Nerve Growth System

Abstract

The nerve regeneration system includes a nerve guide having a proximal end and a distal end. The system includes a nerve growth factor configured to promote growth of axons and associated nerve tissue. The nerve growth factor has a first concentration closer to the proximal end and a second concentration closer to the distal end. The second concentration of growth factor is higher than the first concentration of growth factor. The system includes a myelination factor configured to promote myelination of the grown axons. The myelination factor has a first concentration closer to the proximal end, a third concentration closer to the distal end, and a second concentration of myelination factor between the first and third concentrations of myelination factor. The second concentration of myelination factor is higher than the first concentration of myelination factor and higher than the third concentration of myelination factor.

Description

[Technical field]

[0001] Priority This patent application claims priority to U.S. Provisional Patent Application No. 63 / 327,464, entitled “APPARATUS FOR NERVE GROWTH,” filed April 5, 2022, and listing Mario Romero-Ortega, David Constantine, and Jeffrey Petruska as inventors, the entire disclosure of which is incorporated herein by reference.

[0002] Exemplary embodiments of the present invention relate generally to nerve regrowth, and more particularly, various embodiments of the present invention relate to promoting nerve regrowth using various gradients. [Background technology]

[0003] Nerves are the primary structures of the peripheral nervous system ("PNS"), including associated structures generally outside the brain and spinal cord (i.e., outside the central nervous system, or "CNS"). Nerves are composed of wire-like extensions--axons--of primarily sensory, autonomic, and motor neurons. Thus, nerves are collections of axons, usually one per neuron. Unlike blood vessels, which also extend throughout the body but are composed of many individual cells that connect with each other to form tubes that carry blood, the entire length of an axon is part of a single neuron. Axons are wrapped intermittently along their path by supporting cells known as "Schwann cells." Some of these produce insulation called myelin, a physical structure essential to allow effective conduction of electrical signals (action potentials; APs) carried by axons. Axons also carry chemical signals in both directions between the neuronal cell body (nerve cell body) and target tissues (e.g., spinal cord, skin, muscle, nerves, blood vessels, viscera). In addition, nerves are endowed with a vascular supply to provide nutrients and immune surveillance and to remove waste products.

[0004] Peripheral nerve ("PN") injuries occur in hundreds of thousands of people each year as a result of trauma, disease, or other procedures such as radiation therapy and radical prostatectomy. Many of these cases have damage severe enough to create a gap between the ends of the severed nerve that cannot be bridged by simply acutely stretching the ends and joining them directly. In some cases, the gap is so large that there is currently no treatment that can reasonably be expected to restore it, so the nerve is left unrepaired, often leading to the formation of a painful neuroma.

[0005] Summary of the Invention According to an embodiment of the invention, a nerve regeneration system includes a nerve guide having a proximal end and a distal end. The nerve guide has a housing having one or more ducts. The one or more ducts extend in a direction substantially transverse to a longitudinal axis of the nerve guide. A matrix material is disposed within the housing. The matrix material defines one or more channels extending in a direction substantially along the longitudinal axis of the nerve guide. The system includes a nerve growth factor configured to promote growth of axons and associated nerve tissue. The nerve growth factor has a first concentration closer to the proximal end and a second growth factor concentration closer to the distal end. The second growth factor concentration is higher than the first growth factor concentration. The system includes a myelination factor configured to promote myelination of the grown axons. The myelination factor has a first myelination factor concentration closer to the proximal end, a third myelination factor concentration closer to the distal end, and a second myelination factor concentration between the first myelination factor concentration and the third myelination factor concentration. The second myelinating factor concentration is greater than the first myelinating factor concentration and greater than the third myelinating factor concentration.

[0006] In various embodiments, the channel comprises a channel material containing nerve growth factors and / or myelination factors. In some other embodiments, the matrix may comprise a matrix with nerve growth factors and / or myelination factors. The channel is configured to allow axons to grow through it. The matrix is ​​configured such that axons do not initially grow through it.

[0007] Among other things, the housing may include indicators and neural connections that indicate proper orientation of the device.

[0008] In some embodiments, a first nerve growth factor concentration is at the proximal end of the channel and a second nerve growth factor concentration is near the distal end of the channel. The first myelination factor concentration can be near the proximal end of the channel, the second myelination factor concentration can be near the middle of the channel, and the third myelination factor concentration is near the distal end of the channel.

[0009] In various embodiments, the channel has a substantially linear gradient of growth factor concentration along a longitudinal axis of the channel from a first growth factor concentration to a second growth factor concentration.

[0010] In some embodiments, the channel has a substantial central peak gradient of growth factor concentration along a longitudinal axis of the channel from the first growth factor concentration to the second growth factor concentration.

[0011] The device may be configured to release nerve growth factor from the biodegradable polymer at a first time for a first duration. The device may also be configured to activate myelination factor at a second time for a second duration. In various embodiments, the second time is after the first time and the first duration overlaps in time with the second duration. The second time may be at least one week after the first time. In some embodiments, the second time may be at least two weeks after the first time. Additionally, the second time may be about 20 days after the first time.

[0012] The release rate of the nerve growth factor can increase from a first growth factor concentration to a second growth factor concentration. The channel can include a secondary nerve growth factor. The channel has a first secondary growth factor concentration closer to a proximal end and a second secondary growth factor concentration closer to a distal end. The second secondary growth factor concentration can be higher than the first secondary growth factor concentration.

[0013] Among others, the growth factors and / or secondary growth factors may include nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), insulin-like growth factor-1 (IGF-1), and ciliary neurotrophic factor (CNTF), pleiotrophin (PTN) (also known as heparin-binding growth factor 8, HBGF-8). The myelination factors and / or secondary myelination factors may include neuregulin-1 (also known as acetylcholine receptor-inducing activity (ARIA), breast cancer cell differentiation factor p45, glial growth factor, heregulin (HRG), Neu differentiation factor, sensory and motor neuron-derived factor, NRG1), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), sonic hedgehog (Shh).

[0014] According to another embodiment, a method regenerates an injured nerve having a nerve gap of at least 4 cm. The method provides an injured nerve having a proximal trunk and a distal trunk. A first growth factor concentration is provided closer to the proximal trunk and a second growth factor concentration is provided closer to the distal trunk. The second growth factor concentration is higher than the first growth factor concentration. The first myelinating factor concentration is provided closer to the proximal trunk. The third myelinating factor concentration is provided closer to the distal trunk. The second myelinating factor concentration is provided between the first myelinating factor concentration and the third myelinating factor concentration. The second myelinating factor concentration is higher than the first myelinating factor concentration and higher than the third myelinating factor concentration. The method restores function of the nerve across a gap of at least 4 cm.

[0015] In particular, the provision of the growth factor is initiated at a first time. Similarly, the provision of the myelination factor is initiated at a second time after the axon has regenerated to the point where myelination is possible. In various embodiments, the first time is at least one week prior to the second time. Furthermore, the nerve growth factor is provided for a first duration, and the myelination factor is provided for a second duration. The second duration can be longer than the first duration.

[0016] In various embodiments, at least 60% of the total concentration of myelination factor is released within 200 hours of coupling the device to the nerve. Further, the concentration provided can be between 1 ng / mL and 100 ng / mL.

[0017] Some embodiments may provide a nerve guide having a proximal end and a distal end. The nerve guide may include a biodegradable housing having one or more ducts. The one or more ducts may extend in a direction substantially transverse to a longitudinal axis of the nerve guide. The nerve guide may also include a matrix material disposed within the housing. The matrix material may define one or more channels extending in a direction substantially along the longitudinal axis of the nerve guide.

[0018] The first growth factor concentration can be closer to the proximal trunk and the second growth factor concentration can be closer to the distal trunk. The second growth factor concentration can be higher than the first growth factor concentration. The method can provide the myelination factor at a third time that is at least one week prior to the second time.

[0019] Various embodiments may provide a secondary nerve growth factor. A first secondary growth factor concentration may be closer to the proximal end and a second secondary growth factor concentration may be closer to the distal end. The second secondary growth factor concentration may be higher than the first secondary growth factor concentration. Similarly, a secondary myelination factor may be provided.

[0020] In various embodiments, the matrix is ​​formed from agarose. The channels may comprise collagen.

[0021] Those skilled in the art will be able to more fully appreciate the advantages of various embodiments of the present invention from the following "Description of Exemplary Embodiments," which is described with reference to the drawings summarized immediately below. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a schematic diagram illustrating a cross-sectional view of a nerve according to an exemplary embodiment. [Diagram 2] 1A-1D are schematic diagrams illustrating the process of peripheral nerve injury according to an exemplary embodiment. [Figure 3A] FIG. 2A is a schematic diagram showing a perspective view of a partially transparent representation of a nerve regeneration device according to an exemplary embodiment. [Figure 3B] FIG. 3B is a schematic cross-sectional view of the device of FIG. 3A. [Figure 4A] FIG. 2 is a schematic diagram illustrating details of a channel 52 according to an exemplary embodiment. [Figure 4B] FIG. 2 is a schematic diagram illustrating details of a channel 52 according to an exemplary embodiment. [Figure 4C] FIG. 2 is a schematic diagram illustrating details of a channel 52 according to an exemplary embodiment. [Figure 5A] FIG. 13 is a graphical illustration of an example of nerve growth factor concentration from the proximal end to the distal end, according to an exemplary embodiment. [Figure 5B] FIG. 13 is a graphical illustration of an example of a nerve growth factor release profile from the proximal end to the distal end, according to an exemplary embodiment. [Figure 5C] FIG. 13 is a graphical illustration of an example of nerve growth factor release duration from the proximal end to the distal end, according to an exemplary embodiment. [Figure 6A] FIG. 13 is a graphical illustration of an example of myelination factor concentration from the proximal end to the distal end in accordance with an exemplary embodiment. [Figure 6B] FIG. 13 graphically illustrates an example release profile of a myelination factor from the proximal end to the distal end, according to an exemplary embodiment. [Figure 6C] FIG. 13 is a graphical illustration of an example of myelination factor release duration from the proximal end to the distal end, according to an exemplary embodiment. [Figure 6D] FIG. 2 is a schematic diagram illustrating an example of a cumulative release pattern of a myelination factor over time, according to an exemplary embodiment. [Figure 6E] FIG. 2 is a schematic diagram illustrating an example of a cumulative release pattern of nerve growth factor and myelination factor, according to an exemplary embodiment. [Figure 7] FIG. 1 illustrates a method for regenerating nerves, according to an exemplary embodiment. [Figure 8] FIG. 13 is a schematic diagram illustrating channels with exemplary concentrations, release times, and release rates of nerve growth factor and myelination factor, respectively, according to an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In an exemplary embodiment, damaged (e.g., severed) nerves are regenerated, particularly along long gaps (e.g., 2 cm, 3 cm, 4 cm, and longer). The nerves are regenerated by providing nerve growth factors and myelination factors (collectively, factors) within the gap. The factors are each provided to the gap at a given concentration gradient. The factors are released at different times from each other. Furthermore, in some embodiments, each of the factors has a different time release pattern / gradient along the length of the gap.

[0024] Additionally, various embodiments include a device that couples with the proximal and distal trunks of a nerve. The device is configured to contain nerve growth factors and myelination factors at predetermined concentrations. The factors are configured to provide a predetermined release pattern (e.g., gradient) upon implantation. In particular, the device is configured to provide a given release pattern for each of the factors throughout the nerve's growth cycle to advantageously promote growth and myelination of the injured nerve so that the nerve's axons can grow across the gap for long periods of time. Effective use of this combination device allows growth across shorter and longer nerve gaps. Details of exemplary embodiments are discussed below.

[0025] 1 illustrates a schematic cross-sectional view of a nerve 10 according to an exemplary embodiment. The discussion of the various embodiments relates to a peripheral nerve 10. However, the exemplary embodiments may also include a central nerve 10.

[0026] Nerve 10 is an enclosed, cable-like bundle of nerve fibers (called axons 16). Each axon 16 is an extension of an individual neuron, with some other supporting cells, such as Schwann cells, covering the axon 16 in myelin 18. As used herein, the proximal end 12 refers to the end of the neuron closer to the spine (e.g., the nucleus of the neuron). Thus, the axon 16 grows outward away from the neuron toward the distal end 14 (e.g., closer to the innervated muscle).

[0027] Each nerve 10 is covered on the outside by a dense sheath of connective tissue called the epineurium 20. Beneath the epineurium 20 is the perineurium 22, a layer of fat cells, which forms a nearly complete sleeve around the bundle of axons 16 (called the nerve bundle). The endoneurium 24 (also called the endoneurial channel, endoneurial sheath, endoneurial tube, or Henle's capsule) is a layer of delicate connective tissue surrounding the myelin 18 sheath of each myelinated axon 16 in the peripheral nervous system. In an undamaged nerve 10, the endoneurium 24 forms an unbroken tube from the surface of the spinal cord to the level where the axon 16 synapses with its muscle fibers and / or terminates at a sensory receptor. The endoneurium 24 consists of an inner sleeve of a material called the glycocalyx and an outer delicate meshwork of collagen fibers. Although not shown in FIG. 1, the nerve 10 also contains blood vessels throughout.

[0028] As mentioned above, the axon 16 is intermittently enveloped along its path by supporting cells known as Schwann cells. Some of these cells produce insulation called myelin 18, whose physical structure is essential to allow for effective conduction of the electrical signal (action potential; AP) carried by the axon. The regenerating axon 16 may encounter areas of transplanted conduits or native denervated nerves that have no or few Schwann cells. Without Schwann cells, portions of the axon 16 in these areas will not be metabolically supported or myelinated by Schwann cells. As discussed herein, various signals can promote the migration of Schwann cells into transplanted conduits, foster and promote their proliferation in conduits and nerves, and prevent or reverse their aging. Various signals can also affect the properties of myelination - its quality (compactness, thickness) and spacing - which greatly affect the fidelity, velocity, and frequency of APs that can be conducted by the axon and thus its effectiveness in driving muscle contraction (in the case of motor axons) and sensation (in the case of sensory axons).

[0029] FIG. 2 illustrates a schematic of the process of peripheral nerve 10 injury according to an exemplary embodiment. The nerve may include vasculature 26, sensory axons 16A, motor axons 16B, and / or autonomic axons. Peripheral nerve 10 injury occurs to hundreds of thousands of people each year as a result of trauma, disease, or other treatments, including radiation therapy and radical prostatectomy. Many of these cases have damage severe enough to create a gap 28 between the ends of the severed nerve 10 that cannot be bridged by simply acutely stretching the ends and joining them directly. These cases generally require the insertion of some auxiliary device to fill the gap 28 in an effort to restore function. Some gaps 28 are so large that prior art techniques do not provide reliable treatment for recovery, and the nerve 10 is left unrepaired, often leading to the formation of painful neuromas.

[0030] In a nerve injury condition where the axon 16 is severed, as shown in stage 1, the nerve 10 can have a proximal trunk 30 and a distal trunk 32. The portion of the axon 16 that is separated from the nucleus (e.g., the portion of the axon 16 associated with the distal trunk 32) dies, degrades, and the debris is removed by immune cells. Various embodiments support / promote the growth of the axons 16 from the proximal trunk. As the axons 16 are an extension from the nucleus, as they become reconnected to their final target (e.g., muscle), the axons 16 grow from the point where they were severed back to the target (but do not reconnect with the distal cut portion of the axon 16 that is removed by immune cells). This reconnection, shown in stage 4, is the first step in restoring electrical and chemical communication of the nerve. In humans, the distance that the nerve needs to grow can be over a meter long. The distance that an axon 16 ultimately grows when regeneration is successful includes both the distance of the gap 28 and the distance to the final terminal target (e.g., muscle, skin, viscera). Although the overall distance can exceed one meter, the gap 28 caused by injury to the axon 16 is usually quite short.

[0031] Nerve regeneration may require a length of time that renders the distal nerve tissue and target tissue non-receptive to the regenerating axons, preventing successful reconnection and restoration of function. Exemplary embodiments provide chemical agents that provide signals that enhance the rate of regeneration and myelination of axons 16, allowing the denervated nerve and target tissue to cover greater distances before becoming non-receptive.

[0032] Effective and / or precise connections between specific neuronal types (sensory, autonomic, or motor) and specific body locations (skin regions, visceral structures, muscles, etc.) are established during development, with each axon 16 being provided with a connective tissue encasement (endoneurium). If nerve injury severs an axon 16 but does not severs the endoneurium 24, the regenerating axons 16 are generally able to reach their original targets. However, if there is nerve injury that opens the endoneurium 24, the regenerating axons 16 may not be able to find their original targets. The inventors have recognized that certain signals can facilitate axon target discovery such that an increased number of axons 16 can more precisely connect to their appropriate target tissue type.

[0033] Injury to the nerve 10 recruits immune cells to the site of injury. Some types of immune cells may induce failure of axonal regeneration, while other types of immune cells may promote it. Exemplary embodiments provide factors that generate signals to regulate or induce populations of immune cells to migrate to the injury / transplant / regeneration area or to affect changes in immune cells present in the injury / transplant / regeneration area. As a result, such methods and / or devices are configured to regulate axonal regeneration.

[0034] Injury to the nerve 10 also severs the nerve's axons 16 and blood vessels. Although the axons 16 may have the ability to regenerate into the implanted conduit or native denervated nerve segment without the concomitant collection of new lengths of blood vessels, axon 16 growth stalls. Thus, the exemplary embodiments generate and / or promote various signals and mechanical structures to encourage vascularization and allow infiltration of blood vessels into the implantable nerve guide device 34 and regenerated nerve tissue.

[0035] FIG. 3A illustrates a schematic perspective view of a partially transparent representation of a nerve regeneration device 34 according to an exemplary embodiment. FIG. 3B illustrates a schematic cross-sectional view of the device 34 of FIG. 3A. The device 34 serves as a guide and scaffold for the axons 16 and associated neural tissue as they grow toward the distal end 14. The device 34 is configured to assist nerves 10 of various sizes to regenerate and remyelinate axons 16 across small to large gap 28 sizes. It should be noted that FIGS. 3A-3B illustrate various dimensions of the device 34. These dimensions are not intended to be limiting of various embodiments, but merely illustrate the dimensions of one example of the device 34.

[0036] The size of the device 34 is selected to suit a given gap 28 length and nerve 10. In the example of repairing a nerve 10, the diameter of the device 34 is suitable to interface with and attach to the portion of the nerve 10 being repaired (e.g., typically the end of the nerve 10). For other tissues, the face of the device 34 may suitably match the face of the tissue. In the example where the device 34 is intended to span the separated side of the tissue, such as the cut end of a nerve, the device may be sized sufficiently to span the separated side of the tissue. In various embodiments, different sizes of device 34 may be provided to suit different sizes of nerves 10.

[0037] The device 34 contains nerve growth factor 60 (e.g., GDNF) and myelination factor 62 (e.g., NRG1) in concentrations configured to have a specific release pattern that aids in regeneration and / or myelination of the axons 16 of the nerve 10. Thus, proper orientation of the device 34 when coupled to the nerve 10 is important for optimal results in various embodiments. The device 34 has a proximal end 36 and a distal end 38. The proximal end 36 of the device 34 is configured to couple with the proximal trunk 30 of the nerve 10. Similarly, the distal end 38 of the device 34 is configured to couple with the distal trunk 32 of the nerve 10. To that end, the device 34 may include a nerve coupling portion 40 (e.g., an eyelet for receiving a clamp and / or suture) to aid in coupling to the nerve 10. Additionally, the device 34 may include indicators 42 (e.g., markings indicating which ends of the device 34 connect to the proximal trunk 30 and / or distal trunk 32) to indicate to a medical professional the appropriate intended orientation of the device 34 relative to the nerve 10.

[0038] The device 34 has an outer housing 44, preferably formed from a biodegradable material. In some embodiments, the housing 44 may have the shape of a cylindrical tube. However, other embodiments may shape the housing 44 in a variety of ways. For example, the housing 44 may have a substantially rectangular or hexagonal prism shape, among others. Additionally, the outer surface is preferably smooth without sharp edges. In various embodiments, the housing 44 defines a central or longitudinal axis 48 that extends from the proximal end to the distal end of the housing 44.

[0039] The housing 44 has a number of ducts 46 extending therethrough (e.g., in a direction substantially transverse to the longitudinal axis 48). The ducts 46 fluidly connect the exterior of the device 34 within the internal matrix 50 and / or channels 52. The ducts 46 thus provide for infiltration of neovasculature to provide a blood supply to cells / tissues inside the channels 52 / matrix 50. The ducts 46 may also aid in the reconstruction of the perineurium and epineurium.

[0040] Within housing 44 is a matrix 50 that defines (e.g., by the absence of matrix material) a plurality of channels 52 for growth of axons 16. Matrix 50 is formed from a porous material having pores that allow gases and nutrients to pass through but are generally not large enough for growth of axons 16 (although they may become large enough after sufficient degradation of matrix 50 over time). Thus, device 34 is configured such that axons 16 grow within channels 52 and not within matrix 50. In various embodiments, matrix 50 may be formed from, for example, a 1.5% to 2.5% agarose gel.

[0041] The housing 44 provides a rigid structure for the matrix 50 to support the structure of the matrix 50. The material of the housing 44 can be selected to provide additional features such as mechanical strength, as well as attachment points for objects such as surgical sutures and / or biological integration. The housing 44 can contain internal slots such that there are points / channels of separation from the matrix 50 leading from the duct 46 to allow cells / fluids / etc. from outside the device 34 to access the inside of the housing 44 and most of the outside of the matrix 50.

[0042] The matrix 50 defines one or more of the channels 52. FIGS. 3A-3B show the device 34 having eight channels. However, various embodiments may have one or more channels 52. Additionally, the channels 52 may have a variety of cross-sectional shapes (e.g., circular, rectangular, etc.) and dimensions. Inside the channels 52 is a biological gel-forming material that provides an acceptable growth environment for many types of cells (e.g., type 4 collagen). Preferably, the channels 52 are formed from a material that has viscoelastic properties and nutrients suitable for tissue repair.

[0043] In an exemplary embodiment, the minimum internal dimension of the channels in this embodiment may be 40-50 microns, and the maximum internal dimension of the channels 52 may be 1.0-2.0 millimeters. Additionally or alternatively, the matrix 50 may have one to multiple channels (e.g., 8, 12, 15, 20). The total number of channels 52 is a function of the overall size of the device 34 and its goals. The spacing between the channels 52 (i.e., the amount of matrix 50 between the channels) is a function of the material and properties of the matrix 50. There is sufficient matrix 50 between the channels to provide a durable, flexible (if necessary) channel 52 structure for the intended functional durability of the device 34. FIG. 1D shows a schematic of the material of the matrix 50 inside the housing 44, with the channels 52 within the matrix.

[0044] In various embodiments, the matrix 50 and / or the channels 52 contain the factors 60, 62 therein. The factors may be provided in the form of, among others, polylactic-co-glycolic acid (PLGA) microparticles. In some embodiments, the factors 60, 62 may be distributed throughout the channels 52 at a desired spatial concentration. Additionally or alternatively, the factors 60, 62 may be embedded in the matrix 50 and may diffuse into the channels 52 over time. Further, some embodiments may include a fiber wrapped around the exterior of at least one channel 52, the fiber including an active factor operable to diffuse into the interior of the channel 52. The concentration of the factors 60, 62 may be measured over a certain spatial resolution (e.g., unit volume), such as 500 cubic microns. In various embodiments, the concentration of the factors 60, 62 may be continuously increased along the length of the device such that a gradient is formed. The device may include nerve growth factor 60 in a gradient that increases from a first concentration 60A to a second concentration 60B. The device may include myelination factor 62 in a gradient that increases from a first concentration 62A to a second concentration 62B, and then decreases from the second concentration 62B to a third concentration 62C. In various embodiments, a concentration of factor 60 may then be released within channel 52 to provide a similar concentration gradient (even if only temporarily due to diffusion within channel 52).

[0045] Although the matrix 50 is described as being within the housing 44, it should be understood that some embodiments may not include an outer housing 44. Instead, the channels 52 may be formed and held together (at least temporarily) by the matrix 50. The matrix 50 may include ducts 46 and / or have pores large enough for the passage of nutrients and neovasculature.

[0046] 4A-4C are schematic diagrams illustrating details of a channel 52 according to an exemplary embodiment. In particular, FIG. 4A illustrates a close-up view of a single channel 52 of the device 34 of FIG. 4B. Although the growth factor 60 and the myelination factor 62 are shown as being on different sides of the channel 52, this is merely for clarity and is not intended to limit the various embodiments. Thus, in practice, the myelination factor 62 and the growth factor 60 may be intermingled within the channel 52. However, in some embodiments, the myelination factor 62 may be on the inside of a separate channel 52 from the nerve growth factor 60.

[0047] In various embodiments, the device 34 is configured to release at least two different types of factors 60, 62 within the channel 52. As shown, two different types of factors 60, 62 are disposed within the channel 52. However, as previously discussed, other embodiments may include the factors 60, 62 within the matrix 50, the housing 44, and / or the fibers surrounding the channel 52. In various embodiments, the factors 60, 62 may be suspended within the channel 52 by freezing. In some other embodiments, the factors 60, 62 may be incorporated into the matrix 50 and released when the matrix 50 dissolves.

[0048] In various embodiments, the two factors include a nerve growth factor 60 configured to promote growth of axons 16 and associated nerve tissue, and a myelination factor 62 configured to promote myelination of the grown axons 16. Additionally, the myelination factor may aid in axon sorting. The factors 60, 62 may be configured to have different release profiles that aid in axon 16 growth and myelination.

[0049] 4A shows an exemplary concentration profile of factors 60, 62 within channel 52, according to an exemplary embodiment. The concentration profile varies relative to a longitudinal axis 54 of channel 52, which is substantially parallel to longitudinal axis 48 of device 34. Channel 52 has a first nerve growth factor concentration 60A near a proximal end 56 and a second nerve growth factor concentration 60B near a distal end 58. In various embodiments, the concentration of nerve growth factor 60 increases from the first concentration 60A to the second concentration 60B along the longitudinal axis 54 from the proximal end 56 to the distal end 58. Thus, various embodiments provide an increasing concentration gradient from the proximal end 56 to the distal end 58.

[0050] FIG. 5A graphically illustrates an example of a concentration of nerve growth factor 60 from the proximal end to the distal end, according to an exemplary embodiment. For nerve growth factor 60, the X-axis distance depends on the length of the channel 52. However, the first concentration 60A may be about 0 mm to about 0.5 mm from the proximal end 56. As an example, the second concentration 60B may be about 30 mm (e.g., at or near the distal end 58). However, it should be understood that in various embodiments, the distance may be longer or shorter. The first concentration 60A may have a concentration of growth factor 60 of about 0 to about 5 ng / ml. The second concentration 60B may have a concentration of growth factor 60 of about 90 to about 100 ng / ml.

[0051] Although the addition of nerve growth factor 60 independently aids in the growth of axons 16, the inventors have discovered that a longitudinally increasing concentration gradient of nerve growth factor 60 improves the regeneration of axons 16 compared to a substantially constant distribution of nerve growth factor 60 along the longitudinal axis 54. Without wishing to be bound by any particular theory, the inventors believe, but have not confirmed, that the increased growth rate of axons 16 is due to the tendency of axons 16 to grow from regions of low to high concentration of nerve growth factor 60.

[0052] Furthermore, growth of axons 16 is a slow process. Simultaneous release of nerve growth factor 60 along the entire length of channel 52 may undesirably result in premature degradation of growth factor 60 before achieving the intended effect on growing axons 16. Thus, as shown in FIG. 5B, exemplary embodiments may provide a delayed nerve growth factor 60 release profile along the length of channel 52 such that a concentration closer to the proximal end 56 (e.g., first concentration 60A) is released and available to axons 16 before a concentration closer to the distal end 58 (e.g., second concentration 60B). In various embodiments, the release profile along the length of channel 52 is configured to release a significant portion (or all) of the concentration of growth factor 60 substantially coincident with the growth of axons 16 along the longitudinal axis 54.

[0053] Alternatively, the nerve growth factor 60 may be released substantially simultaneously throughout the channel 52 (e.g., within the first 24 hours of implantation). Preferably, when the nerve growth factor 60 is released substantially uniformly (e.g., substantially throughout the length of the channel), the second nerve growth factor concentration 60B has a longer release duration than the first nerve growth factor concentration 60A. As an example, release may begin on day 1 and continue for approximately 15-30 days (e.g., for nerve growth factor 60 such as GDNF). However, the total concentration released may be lower on any given day at the first concentration 60A (e.g., about 0-5 ng / ml) than the second concentration 60B (e.g., 90-100 ng / ml) because it is continuously released and also continuously degraded or taken up by the cells.

[0054] As previously mentioned, various embodiments can modify the drug delivery profile of the nerve growth factor 60 to vary the release duration. For example, as shown in FIG. 5C, a higher concentration of nerve growth factor 60 available near the distal end 68 can be configured to release over a longer period of time than a concentration of nerve growth factor 60 available near the proximal end 56. Thus, the release duration can include a gradient. In some embodiments, the duration of release of the nerve growth factor 60 can be about 10 days to about 20 days near the proximal end 56 (e.g., first concentration 60A) and about 25 days to about 30 days near the distal end 58 (e.g., second concentration 60B).

[0055] It should be understood that some of the concentration may be immediately available and some of the concentration may be permanent, in various embodiments, this is due to the rate of microparticle degradation and thus the release of encapsulated agents 60, 62 or the rate of de-sequestering of agents 60, 62 from the matrix 50.

[0056] Similar to nerve growth factor 60, various embodiments have different concentrations of myelination factor 62 distributed over the length of channel 52. FIG. 6A graphically illustrates an example of a concentration of myelination factor 62 from proximal end 56 to distal end 58, according to an exemplary embodiment. Myelination factor 62 has a first myelination factor concentration 62A near proximal end 56, a third myelination factor concentration 62C near distal end 58, and a second myelination factor concentration 62B between first concentration 62A and third concentration 62C. The concentration of myelination factor 62 increases from first concentration 62A to second concentration 62B along longitudinal axis 54 and decreases from second concentration 62B to third concentration 62C. Thus, various embodiments provide a concentration gradient that increases toward the center of channel 52 and decreases toward the ends of the channel. This type of gradient may be referred to as a central peak gradient. In various embodiments, the concentration of myelination factor 62 can be about 0-5 ng / ml at a first myelination concentration 62A (e.g., near the proximal end 56), about 15-30 ng / ml at a second concentration (e.g., near the center of channel 52), and about 0-5 ng / ml at a third concentration 62C (e.g., near the distal end 58). In various embodiments, myelination factor 62 can include recombinant human NRG1-β1 (Thr176-Lys246, EGF domain; R&D Systems, Minnesota, USA) and / or SDMF fragment.

[0057] The inventors have discovered that a concentration gradient having a peak between two lower concentrations of myelination factor 62 (e.g., near the middle of the length of channel 52) advantageously enables remyelination of regenerating axons 16 of nerve 10 across long gaps 28.

[0058] From experiments, the inventors have determined that the absence of myelinating factors results in some regenerated axons (using the growth factor concentrations discussed above) not being myelinated near the distal end. By using myelinating factors 62, Schwann cells 66 migrate towards the growing axons 16.

[0059] 6B graphically illustrates an example of the time to onset of release of myelinating factor according to an exemplary embodiment. Various embodiments may provide a sustained continuous release of myelinating factor 62 for approximately 25-50 days.

[0060] FIG. 6C graphically illustrates an example of the release duration of myelination factor according to an exemplary embodiment. In some embodiments, the total duration of release varies from the proximal end to the distal end between two different spatial gradients, with the total duration of the central gradient being longer than that of the linear gradient. Exemplary embodiments optionally titrate the composition of the copolymer to tailor the release profile according to the length of the channel. In various embodiments, the release duration of myelination factor 62 is from about 25 days to about 50 days.

[0061] FIG. 6D illustrates generally an example of a cumulative release pattern of myelinating factor 62 over time, according to an exemplary embodiment.

[0062] FIG. 6E illustrates a schematic of an example of a cumulative release pattern of nerve growth factor 60 and myelination factor 62, according to an exemplary embodiment. As shown, there is a time delay between the release of growth factor 60 and the release of myelination factor 62. It should be noted that despite the use of a time delay, there may be some small, unspecified amount of factor 60, 62 (e.g., unencapsulated) immediately available, and an additional supply of factor 60, 62 is released over time. This insubstantial release is generally below a concentration of 1 ng / mL, and this insubstantial release of factor 60, 62 is not considered part of the time delay. Exemplary embodiments release substantial amounts of peptides, proteins, drugs, or molecules, and the substantial release is at a particular concentration (e.g., at least 1-100 ng / mL).

[0063] In various embodiments, nerve growth factors 60 may include nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) (e.g., to promote motor neuron growth), insulin-like growth factor-1 (IGF-1), and ciliary neurotrophic factor (CNTF), pleiotrophin (also known as heparin-binding growth factor 8, HBGF-8) (e.g., to promote sensory neuron growth). Depending on the type of nerve 10, exemplary embodiments titrate any one of these to promote primarily sensory or primarily motor.

[0064] In various embodiments, myelination factors 62 may include neuregulin-1 (NRG1, also known as acetylcholine receptor-induced activity (ARIA), breast cancer cell differentiation factor p45, glial growth factor, heregulin (HRG), Neu differentiation factor, sensory and motor neuron derived factor), platelet derived growth factor (PDGF), fibroblast growth factor (FGF), and sonic hedgehog (Shh). Preferably, myelination factors 62 include neuregulin types 1-3, which are releasable forms that activate Schwann cells and help them become pro-regenerative and pro-myelination.

[0065] Although the addition of myelinating factor 62 independently aids in myelination of axons 16, the inventors have discovered that a longitudinal median peak concentration gradient of myelinating factor 62 improves myelination of axons 16 compared to a substantially constant longitudinal distribution of myelinating factor 62. Although a constant myelinating factor 62 concentration throughout the length of the channel is operable, the majority of grown axons 18 do not myelinate. The inventors estimate from their experiments that of a possible 15,000-20,000 grown axons, approximately 100 will myelinate with a constant myelinating factor 62 concentration. The inventors speculate, but have not confirmed, that the reason for this unexpected result is due to a process called axon sorting. Myelinating factor 62 also aids in axon sorting. When myelinating factor 62 is provided, Schwann cells are prompted to perform sorting - myelination also requires that the axons are "active" (not in terms of growth).

[0066] From our experiments, the outgrowth of axons appears to be time dependent in that myelination factors 62 and growth factors 60 must be introduced at specific times.

[0067] Thus, various embodiments provide a time delay between the release of the growth factor and the release of the myelination factor 62. For example, the myelination factor 62 may be released 1-4 weeks after the release of the growth factor 60 begins (e.g., about 18-22 days after the release of the growth factor 60 begins). Preferably, the release of the myelination factor is a function of the growth rate of the axons 16. The axons 16 grow to a point near the center of the device 45 at different times based on the overall length of the device. For example, the axons 16 reach the center much faster in a 2 cm long channel than in a 6 cm long channel. Exemplary embodiments pre-adjust the temporal release profile of the factors 60, 62 to account for this time difference in axon arrival times.

[0068] FIG. 7 illustrates a method of regenerating a nerve 10 according to an exemplary embodiment. It should be noted that this method is substantially simplified from a more lengthy method that may typically be used. Thus, the method illustrated in FIG. 7 may have many other steps that one skilled in the art would likely use. Furthermore, some of the steps may be performed in a different order than shown, or simultaneously. For example, in some embodiments, step 706 may begin in parallel with or before step 702, and may have a longer duration. Furthermore, in some embodiments, some of these steps may be optional. Thus, method 700 is merely illustrative of one method according to an exemplary embodiment of the present invention. As such, one skilled in the art may modify the method as appropriate.

[0069] The method of Fig. 7 is described with reference to Fig. 8, which shows a schematic of a device coupled to an injured nerve 10, having various factor concentrations, according to an exemplary embodiment. Fig. 8 shows a schematic of a magnified single channel 52. This is for discussion purposes only, and it should be understood that the device 34 may contain multiple channels 52 having the same or different growth factors 60, 62, growth factor concentrations, and / or release characteristics. Thus, for simplicity, the device 34 and the channel 52 are shown as having the same longitudinal axis 48 / 54 that are substantially parallel.

[0070] The method begins at step 702 with coupling a nerve guide device 34 to the injured nerve 10. The physician identifies the length of the gap 28 of the injured nerve 10 and selects an appropriately sized device 34. To that end, exemplary embodiments may provide a kit including several devices 34 to accommodate various sizes of gap 28 lengths and / or time since the patient sustained injury (e.g., within 24 hours, within a week, etc.). The distribution and release of factors 60, 62 embedded within the device 34 may be tailored to the growth of the axon 18 based on the particular patient's circumstances.

[0071] After selecting the appropriate device 34, the surgeon couples the device 34 to the nerve 10. To that end, the device 34 may include an indicator 42 or other markings to indicate the proper orientation (e.g., proximal vs. distal) of the device 34 relative to the nerve 10. The surgeon uses the connectors 40 of the device 34 to couple to the respective nerve trunks 30, 32. Although FIG. 8 shows the device 34 being sutured to the nerve 10, any conventional method of attachment to a nerve may be used.

[0072] It should be noted that while various embodiments refer to the use of device 34, some embodiments may use similarly configured nerve grafts or other scaffolds (e.g., dissolvable) that include factors 60, 62 of various concentrations and release profiles as described herein.

[0073] In various embodiments, the housing 44 is directly coupled to the epineurium 20. Inside the housing 44 is a matrix 50 that defines one or more channels 52. The channels 52 may be similar in size to the perineurium 22. However, the channels 52 are not necessarily aligned with the perineurium 22, as the axons 16 can travel into the channels 52.

[0074] It should be understood that the various embodiments do not necessarily attempt to reconnect the axons 16 on the proximal trunk 30 to the remaining portions of the axons 16 on the distal trunk 32. The axons 16 on the distal trunk 32 generally die because the axons 16 have been severed from the cell bodies that provide the proteins. However, other cells in the neural tissue remain, but some new cells are recruited because some cells, particularly Schwann cells, can change their phenotype over time. Thus, the device 34 may connect with various remaining portions of the distal trunk 32, such as the perineurium 22 scaffold. The exemplary embodiments provide a scaffold for the neurons to grow back to their original target. Thus, the distal portions of the neurons can be regrown.

[0075] After injury, the distal trunk 32 may contain all nerve tissue except for the axon 16. This is because immune cells remove the distal end of the axon. An exemplary embodiment uses a device to connect two trunks of a severed nerve. However, the axons of the distal trunk separate and the exemplary embodiment regrow inside the distal trunk.

[0076] When injury occurs, insulating Schwann cells in the distal stems 32 are reactivated by inflammation, demyelinating, and becoming pro-regenerative. Schwann cells must align and secrete growth and pro-myelinating factors. Schwann cells are actively involved in several processes including attracting axons 16, enveloping axons, sorting axons, etc.

[0077] In the absence of the exemplary embodiments, over time, reconnection / regrowth is delayed (e.g., proximal axons grow 1-2 mm / day based on gap size). By the time the axon 16 reaches the distal trunk 32, the portion of the axon 16 that is still attached to the distal trunk 32 becomes non-responsive and does not secrete endogenous growth factors. Thus, the exemplary embodiments provide growth factors 60 that aid in the growth of the axon 16. By providing growth factors 60 to the pathway / scaffold, the exemplary embodiments motivate the proximal axon 16 to grow there. Thus, the nerve growth factors 60 help drive the axons 16, and the myelination factors 62 help the Schwann cells not stop prematurely. As discussed below, the factors 60, 62 are provided at different times and at different concentration gradients. Furthermore, Schwann cells that reside further distally in the distal trunk 32 and that do not have contact with the axon 16 for a certain threshold amount of time become "senescent," stop producing growth factors, and no longer sufficiently support the regeneration of the axon 16 to enable effective regeneration of the axon 16 to the target.

[0078] In step 704, nerve growth factor 60 is provided with a given concentration gradient 64A, release time gradient 66A, and / or release rate gradient 68A. As discussed above, concentration gradient 64A is relative to a dimension (e.g., longitudinal axis 54) of channel 52. Initial release time 66A may provide a gradient along longitudinal axis 48 / 54 for nerve factor 60. Release rate gradient 68A defines the rate at which the concentration of factor 60 is released after the initial release time. Although release rate 68A is shown as having a gradient, in some embodiments, release rate 68A may be continuous. In various embodiments, the duration of release of nerve growth factor 60 may be approximately 15-30 days after release begins. As used herein, the term release is considered to encompass substantial release, i.e., release of greater than 1 ng / mL.

[0079] Nerve growth factors 60 may include nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), insulin-like growth factor-1 (IGF-1), and ciliary neurotrophic factor (CNTF), pleiotrophin (PTN) (also known as heparin-binding growth factor 8, HBGF-8), among others. Various embodiments may include multiple nerve growth factors. At least one, and preferably all, of the nerve growth factors have the proposed spatial and temporal gradients, respectively, described herein. For example, some embodiments may include GDNF and PTN, at least one of which has the concentration and temporal gradients described herein (preferably, both nerve growth factors 60 have the concentration gradient 64A, time release gradient 66A, and / or release rate gradient 68A described herein). Various embodiments may use GDNF for motor nerves and PTN for sensory nerves. Some embodiments may include both (eg, where nerve 10 has a combination of motor neurons, sensory neurons, and autonomic neurons).

[0080] As shown, the growth factor 60 may be provided in increasing concentrations along the length of the channel 52. For the reasons discussed above, the concentration of growth factor 60 may be triggered to release in a time-release manner. For example, the concentration closest to the proximal end may be released at an initial time T1, with release of subsequent concentrations occurring at later times along the length of the channel 52 (e.g., represented by times T2, T3, T4, and T5). Additionally, the release rate 68A of the growth factor 60 may vary along the length of the channel 52. In the example shown, the release rate 68A may be lowest near the proximal end 56 and may increase toward the distal end 58.

[0081] In some embodiments, T1 may correspond to the first day (i.e., day 1) of implantation of the device 34. Thus, in various embodiments, the nerve growth factor 60 may begin to release immediately after implantation or within the first 24 hours after implantation.

[0082] The method then proceeds to step 706 of growing the axon 16 and associated nerve 10 tissue. In part, this growth is due to the addition of nerve growth factor 60 from step 704. However, some of the growth may be caused by the body's natural regeneration. When dealing with large gaps 28 (e.g., 2 cm or more, especially 4 cm or more), the body's regenerative capabilities may not be able to regenerate a sufficient length of axon 16, even when a simple nerve guide 34 is provided (e.g., without the factors described herein). For particularly long lengths (e.g., 4 cm or more, especially 5 cm or more), an exemplary embodiment has both myelinating factors 62 and growth factors 60 to adequately regenerate a fully myelinated axon 16.

[0083] The method then proceeds to step 708 of providing myelination factor 62 with a given concentration gradient and time release gradient. Similar to growth factor 60, myelination factor 62 may have its own inherent concentration gradient 64B, release time gradient 66B, and / or release rate gradient 68B. Concentration gradient 64B is relative to a dimension of channel 52 (e.g., longitudinal axis 54). Initial release time 66B may provide a gradient along longitudinal axis 48 / 54 for myelination factor 62. Release rate 68B defines the rate at which the concentration of myelination factor 62 is released after the initial release time. Although release rate 68B is shown as having a gradient, in some embodiments release rate 68B may be continuous. In various embodiments, the duration of release of myelination factor 62 may be approximately 25-50 days after release begins.

[0084] In some embodiments, T3 may correspond to about 15 to about 25 days after implantation of device 34. Thus, in various embodiments, myelination factor 60 may begin to be released after axon 16 growth has commenced.

[0085] Myelination factors 62 may include, among others, neuregulin-1 (NRG1, also known as acetylcholine receptor-inducing activity (ARIA), breast cancer cell differentiation factor p45, glial growth factor, heregulin (HRG), Neu differentiation factor, sensory and motor neuron-derived factor), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), sonic hedgehog (Shh). Furthermore, myelination factors 62 may include one or more isoforms that have been classified as type I NRG (isoforms with an Ig domain and a glycosylation domain, isoforms 1-8), type II NRG (isoforms with an Ig domain but no glycosylation domain, isoform 9), type III NRG (isoforms with a Cys-rich domain, isoform 10) and type IV NRG (isoforms with an additional 5' exon, isoform 11). All of these isoforms serve different tissue-specific functions. Myelination factor 62 may also include any natural or synthetic ligand for ERBB3 and ERBB4 tyrosine kinase receptors for remyelination, as well as tyrosine kinases that bind with high affinity to specific neurotrophins. For example, there are three known Trk receptors: TrkA, which binds to NGF; TrkB, which binds to BDNF and NT-4 / 5; and TrkC, which binds to NT-3. Various embodiments may include multiple myelination factors 62. At least one, and preferably all, of the myelination factors 62 used have the proposed spatial and temporal gradients, respectively, described herein.

[0086] As shown, myelination factor 62 may be provided in various concentrations along the length of channel 52. Advantageously, the concentration of myelination factor 62 may be configured to provide a peak concentration 64B near the center of channel 52. In the case of myelination factor 62, a central gradient advantageously drives Schwann cells from both ends into the device quickly. This concentration helps Schwann cells from proximal and distal trunks 30 and 32 to meet / connect near the center. Without a concentration of myelination factor 62 along the long gap 28, Schwann cells from proximal and distal trunks 30 and 32 would not be motivated to reach and connect, resulting in incompletely or unmyelinated axons 16.

[0087] The myelination factor 62 may be triggered to release in a time-release manner. For example, the concentration closest to the proximal end may be released at an initial time T3, which is after the initial nerve growth factor 60 release time T1. Subsequent releases of the concentration may occur at later times (e.g., represented by times T3, T4, and T5) along the length of the channel 52. Additionally, the release rate of the myelination factor 62 may vary along the length of the channel 52. In the example shown, the release rate may be lowest near the proximal end 56 and increase toward the distal end 58.

[0088] In various embodiments, the growth factors 60 and myelination factors 62 are not released at substantially the same time or in substantially the same pattern. The illustrative embodiments account for the different physiological occurrences in the proximal and distal trunks 30 and 32. In particular, the proximal trunk 30 contacts the growing axon 16. The myelination factors 62 at the distal end help recruit Schwann cells to perform remyelination.

[0089] In part, the inventors believe that the staggering is beneficial because Schwann cells have multiple modes. It can be disadvantageous to lose myelinating factor (e.g., thereby losing factor supply) before an axon is nearby and ready to myelinate. Unused factor degrades, diffuses, is internalized, and is removed. If a high concentration of myelinating factor is provided before an axon is close enough to myelinate, the myelinating factor may undesirably change how the Schwann cells respond. Thus, an exemplary embodiment delays the release of myelinating factor until an axon is inside the tract and positioned to be myelinated.

[0090] Thus, the release of the two factors 60, 62 is staggered and the exemplary embodiments provide a sequence of events: first, the axon 16 is grown using nerve growth factor 60, and then the grown axon is remyelinated with the aid of myelination factor 62. Various embodiments achieve this staggered delivery using controlled delivery of encapsulant / polymer mixtures, as known to those skilled in the art.

[0091] Returning to FIG. 7, the next step 710 is regenerating the nerve 10. The regenerated nerve 10 may regenerate to cover gaps 28 of various lengths. Some embodiments may grow and myelinate axons 16 for gaps 28 from the nerve cell body (e.g., near the spinal cord) to the length of the target. Exemplary embodiments allow for regeneration of long gaps 28 (e.g., 2 cm or more, 4 cm or more, or 6 cm or more), in addition to regeneration of short gaps 28. Notably, successful regeneration of nerve 10 includes regrowth of multiple axons 16 to their original or other suitable target destination, and further myelination of the regrown portions of axons 16.

[0092] In practice, regeneration of nerve 10 can be tested by evoked sensory function (evoked is distinguished from spontaneous, which may result from abnormal activity in the injured nerve), motor control (reflex or voluntary), or autonomic function. Tests to determine if nerve 10 has regenerated may include, among others: Restoration of static two-point discrimination in affected fingers; · Change in PROMIS Pediatric Upper Limb / Parent Surrogate Upper Limb (PUE / PPUE) outcome assessments postoperatively; · Change in visual analog scale (VAS) postoperative pain score; · Change in reported pain using the Faith Pain Scale-Revised scale (FPS-R) assessment after surgery; · Changes in sensory function as measured by the Medical Research Council Classification of Sensory Recovery (MRCC); · Change in motor function as measured by the Medical Research Council Classification of Motor Recovery (MRCC); Changes in motor function as measured by grasping and pinching; and / or Changes in Tinel's sign

[0093] As an example, evaluation of nerve regeneration includes Tinel's sign, which is an induced assessment of regeneration of axons 16 in the distal trunk 32. Sensation can be induced by electrically or mechanically stimulating the nerve segment distal to the repair site. Because the growing axons 16 are mechanosensitive, poking the nerve 10 (e.g., by pressing the skin) can induce them to fire an action potential. Electrical stimulation can activate the axons 16 wherever they are, so it can be gradually progressed further distally along the nerve's path until no further sensation is induced. This sign provides an indication of the progression of regeneration. A successful measurable outcome is the elicitation of sensation (normal or abnormal) in the body area previously innervated by the stimulated nerve (e.g., distal to the cut end of the proximal stump, including inside the device). There will likely be sensation induced from tissues covering the regenerating axons of the distal nerve, but these are ignored as not part of the test.

[0094] As yet another example, autonomic function (sweating) via galvanic skin response (GSR) can be used to assess nerve regeneration. GSR increases local temperature to induce a local response in which the autonomic nervous system activates sweat glands in the heated area. This causes a decrease in the electrical resistance of the skin, which can be detected (GSR). By heating the denervated area, one can measure when and to what extent GSR returns as an indicator of regeneration of damaged autonomic axons. Successful measurable outcomes include the presence of sweat in the heated area, as long as the sweating area is an area that was denervated by injury and is now experiencing restored sweating function.

[0095] The method 700 then ends.

[0096] It should be understood that in some embodiments, some steps may be optional or skipped. For example, when dealing with short gap injuries, some embodiments may omit the myelination factor. A sufficiently short gap 28 can be remyelinated using the body's natural regenerative abilities. However, the inventors have discovered that using a combination of growth factors 60 and myelination factors 62, the nerve 10 can be regenerated over a long gap.

[0097] Although various embodiments refer to the channel 52 having a given concentration, as previously discussed, the factors 60, 62 may be disposed in various locations throughout the device. Thus, discussion of concentrations within the channel 52 is not intended to limit the placement of the factors 60, 62 of the various embodiments. In exemplary embodiments, the concentrations of factors 60, 62 described herein may be similarly disposed in any portion of the device (e.g., matrix, housing, etc.) and / or any portion of the device, alone or in combination with another portion of the device, may be configured to release the factors 60, 62 into the channel at a predetermined concentration as described herein.

[0098] As used herein and in the claims, the singular forms "a," "an," and "the" refer to plural referents unless the context clearly dictates otherwise. For example, a reference to the singular "the channel" includes a plurality of channels, and a reference to the singular "the nerve growth factor" includes one or more nerve growth factors known to those of skill in the art. Thus, in various embodiments, any reference to the singular can include the plural, and any reference to more than one component can include the singular.

[0099] While various embodiments of the present invention have been described and illustrated herein, those skilled in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the embodiments of the present invention described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the particular application or applications in which the teachings of the present invention are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein.

[0100] Thus, the foregoing embodiments are presented by way of example only, and it should be understood that, within the scope of the appended claims and their equivalents, the embodiments of the invention may be practiced otherwise than as specifically described and claimed. Exemplary embodiments of the present disclosure relate to each individual feature, system, article, material, kit, and / or method described herein. Moreover, any combination of two or more such features, systems, articles, materials, kits, and / or methods is within the inventive scope of the present disclosure, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent. The disclosed embodiments, or portions thereof, may be combined in ways not listed above and / or not explicitly claimed. Thus, one or more features from the various disclosed examples and embodiments may be combined in various ways. For example, it should be understood that the present disclosure contemplates that, to the extent possible, one or more features of any embodiment may be combined with one or more features of any other embodiment.

[0101] Various inventive concepts may be embodied as one or more methods, examples of which are provided. The operations performed as part of a method may be ordered in any suitable manner. Thus, while shown as sequential operations in the exemplary embodiment, embodiments can be constructed in which operations are performed in an order different from that illustrated, which may include performing some operations simultaneously.

[0102] While the above discussion discloses various exemplary embodiments of the present invention, it will be apparent to those skilled in the art that various modifications may be made which will achieve some of the advantages of the present invention without departing from the true scope of the invention.

Claims

1. a nerve guide having a housing having a proximal end and a distal end and having one or more ducts, the one or more ducts extending in a direction substantially transverse to a longitudinal axis of the nerve guide; a matrix material disposed within the housing and defining one or more channels extending in a direction substantially along the longitudinal axis of the nerve guide; A nerve regeneration device comprising: The channel comprises: a nerve growth factor configured to promote the growth of axons and associated neural tissue, the channel having a first concentration of growth factor closer to the proximal end and a second concentration of growth factor closer to the distal end, the second concentration of growth factor being greater than the first concentration of growth factor; a myelination factor concentration configured to promote myelination of the grown axons, the channel having a first myelination factor concentration closer to the proximal end, a third myelination factor concentration closer to the distal end, and a second myelination factor concentration between the first myelination factor concentration and the third myelination factor concentration, the second myelination factor concentration being greater than the first myelination factor concentration and greater than the third myelination factor concentration; A nerve regeneration device comprising a channel material containing:

2. The nerve regeneration device of claim 1 , wherein the housing includes an indicator that indicates proper orientation of the device.

3. the first nerve growth factor concentration is at the proximal end of the channel and the second nerve growth factor concentration is at the distal end of the channel; The nerve regeneration device of claim 1, wherein the first myelinating factor concentration is at the proximal end of the channel, the second myelinating factor concentration is at the center of the channel, and the third myelinating factor concentration is at the distal end of the channel.

4. The nerve regeneration device of claim 1 , wherein the channel has a substantially linear gradient of growth factor concentration along the longitudinal axis of the channel from the first growth factor concentration to the second growth factor concentration.

5. The nerve regeneration device of claim 1 , wherein the channel has a substantial central peak gradient of growth factor concentration along the longitudinal axis of the channel from the first growth factor concentration to the second growth factor concentration.

6. releasing said nerve growth factor from the biodegradable polymer at a first time for a first duration; Activating the myelination factor for a second duration at a second time. It is structured as follows: The nerve regeneration device of claim 1 , wherein the second time is after the first time and the first duration overlaps in time with the second duration.

7. The nerve regeneration device of claim 6 , wherein the second time is at least two weeks after the first time.

8. The nerve regeneration device of claim 6 , wherein the release rate of the nerve growth factor increases from the first growth factor concentration to the second growth factor concentration.

9. The channel is Secondary Nerve Growth Factor 2. The nerve regeneration device of claim 1, comprising collagen containing: wherein the channel has a first secondary growth factor concentration closer to the proximal end and a second secondary growth factor concentration closer to the distal end, the second secondary growth factor concentration being higher than the first secondary growth factor concentration.

10. 1. A method of regenerating a damaged nerve having a nerve gap of at least 4 cm, comprising: providing an injured nerve having a proximal trunk and a distal trunk; providing a first concentration of growth factor closer to the proximal stem and a second concentration of growth factor closer to the distal stem, the second concentration of growth factor being greater than the first concentration of growth factor; providing a first concentration of myelinating factor closer to the proximal stem, a third concentration of myelinating factor closer to the distal stem, and a second concentration of myelinating factor between the first and third concentrations of myelinating factor, the second concentration of myelinating factor being greater than the first concentration of myelinating factor and greater than the third concentration of myelinating factor; restoring function of the nerve over a gap of at least 4 cm; The method includes:

11. providing the growth factor begins at a first time; providing said myelination factor begins at a second time after axons have regenerated to the point where myelination is possible, said first time being at least two weeks prior to said second time; The method of claim 10.

12. providing said nerve growth factor for a first duration; providing said myelination factor for a second duration, said second duration being longer than said first duration; The method of claim 10.

13. 13. The method of claim 12, wherein at least 60% of the total concentration of myelinating factor is released within 200 hours of coupling the device to the nerve.

14. Providing a nerve guide having a proximal end and a distal end. and wherein the nerve guide further comprises: a biodegradable housing having one or more ducts extending in a direction substantially transverse to a longitudinal axis of the nerve guide; a matrix material disposed within the housing and defining one or more channels extending in a direction substantially along the longitudinal axis of the nerve guide; 13. The method of claim 12, comprising:

15. providing a first concentration of growth factor closer to the proximal stem and a second concentration of growth factor closer to the distal stem, the second concentration of growth factor being greater than the first concentration of growth factor; providing said myelination factor at a third time that is at least one week prior to said second time; The method of claim 12 further comprising:

16. The method of claim 14 , wherein the matrix comprises agarose.

17. The method of claim 14 , wherein the channel comprises collagen.

18. 13. The method of claim 12, wherein the growth factors comprise at least one of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), insulin-like growth factor-1 (IGF-1), and ciliary neurotrophic factor (CNTF), or pleiotrophin (PTN).

19. 13. The method of claim 12, wherein the myelination factor comprises at least one of neuregulin-1 (NRG1, also known as acetylcholine receptor-induced activity (ARIA), breast cancer cell differentiation factor p45, glial growth factor, heregulin (HRG), Neu differentiation factor, sensory and motor neuron-derived factor), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), or sonic hedgehog (Shh).

20. a nerve guide device having a housing having a proximal end and a distal end and having one or more ducts, the one or more ducts extending in a direction substantially transverse to a longitudinal axis of the nerve guide, and a matrix material disposed within the housing and defining one or more channels extending in a direction substantially along the longitudinal axis of the nerve guide; configured to promote the growth of axons and associated neural tissue; a nerve growth factor, the device being configured to provide a first concentration of growth factor closer to the proximal end and a second concentration of growth factor closer to the distal end, the second concentration of growth factor being greater than the first concentration of growth factor; configured to promote myelination of the grown axons; the device is configured to provide a first myelinating factor concentration closer to the proximal end, a third myelinating factor concentration closer to the distal end, and a second myelinating factor concentration between the first myelinating factor concentration and the third myelinating factor concentration, the second myelinating factor concentration being greater than the first myelinating factor concentration and greater than the third myelinating factor concentration; A neural regeneration system comprising:

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