Methods and compositions for nerve regeneration

Abstract

Methods and compositions for modulating growth of a neuron with a Wnt, a Wnt-like substance, and / or a chemical compound affecting a Wnt signaling pathway are disclosed. Also disclosed are methods for identifying a substance that modulates growth of a neuron by obtaining a candidate substance and contacting the candidate substance with the neuron are disclosed and methods for modulating growth of a neuron in a subject using a Wnt, a Wnt-like substance, and / or a chemical compound affecting a Wnt signaling pathway. The Wnt, Wnt-like substance, and / or chemical compounds affecting a Wnt signaling pathway can be delivered to the subject using gene therapy techniques. Also disclosed are pharmaceutical compositions for modulating growth of a neuron in a mammal that include a Wnt or a Wnt-like substance. Methods and compositions for inhibiting growth of a neuron are also disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. application Ser. No. 10 / 847,972 filed May 17, 2004, which claims the benefit of U.S. Provisional Application No. 60 / 470,913 filed May 15, 2003, and both are incorporated herein by reference in their entireties.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to the fields of molecular biology, cell biology, pharmacology, developmental neuroscience, neurology, neurosurgery and regenerative biology. More particularly, it concerns methods and compositions for modulating regeneration of a nerve cell using a Wnt, a Wnt-like substance, and / or a chemical compound affecting a Wnt signaling pathway. It also concerns methods and compositions for inhibiting growth of a neuron using inhibitors of neuronal growth that act via the Wnt signaling pathways, such as a Secreted Frizzled-Related Protein (sFRP), sFRP-like substance, Ryk, or Ryk-like substance.[0004...

AI Technical Summary

Benefits of technology

[0019]The inventor has further found that a different set of Wnt proteins pattern the connections of corticospinal tract (CST) axons projecting along the opposite direction by a repulsive mechanism. CST axons project from the motor cortex of the brain to the spinal cord motor circuits and send voluntary movement signals from the brain to the body. Several Wnt genes were found to be expressed at the dorsal funiculus in an anterior-to-posterior decreasing gradient at the cervical spinal cord, where CST axons first enter the spinal cord and a anterior-to-posterior increasing gradient at the lumbar spinal cord level, forming a “half-pipe” gradient. Wnt1 and Wnt5a can repel CST axons in collagen gel assays. A repulsive Wnt receptor, Ryk (Oshikawa et al., 2003; Halford et al., 2000), is expressed in the CST axons and can be detected at the pyramidal decussation and in the dorsal funiculus. Antibodies against the ectodomain of Ryk can block the repulsion of Wnt1. Finally, intrathecal injection of a Wnt inhibitor, secreted Frizzled related protein 2 (sFRP2), at the rostral cervical level (C1 and C2), can inhibit the posterior growth of CST axons in vivo, leading to weaker grip strength.

[0053]In some cases, it will be beneficial to apply one or more Wnt to the site of a spinal cord injury, such that the Wnt(s) will provide attractive guidance to those neurons that need to be attracted to the site of injury during regeneration and repellant guidance to those neurons that need to grow away from the site of injury during regeneration. In this regard, Wnt(s) applied at the site of an injury will provide directional guidance to axonal growth and cause sensory neurons to grow up through the site of the injury and repel motor neurons to grow down through the site of the injury. Further, in this embodiment, it may be beneficial to inhibit the Ryk pathway at the site of the injury so that motor neurons growing through the site of the injury are not inhibited by any Wnts present in the injury site, whether those Wnts are applied to the injury site, or expressed there as a result of normal adult Wnt expression or injury-induced Wnt expression. One may also apply a blocker of myelin inhibitors to the injury site, to prevent such inhibitors from impacting the growth of sensory neurons through the site.

Problems solved by technology

Unlike the peripheral nervous system, damage to the central nervous system axons, such as spinal cord axons cannot be repaired, causing permanent impairment of neural function, such as in paralysis.

The majority of broken necks and broken backs, or vertebral fractures, do not cause any spinal cord damage; however, in 10-14% of the cases where a vertebral trauma has occurred, the damage is of such severity it results in damage to the spinal cord.

Treatment options for patients with spinal cord injuries are limited.

Often, patients with SCI are left with severe, permanent disabilities.

A major reason for the limited availability of treatment options is the fact that there is little known about factors that can control and modulate nerve growth and regeneration following spinal cord injury.

The expression pattern of the Slits and Semaphorins identified in these studies have been examined, but no anterior-posterior gradient of these chemorepellents in the spinal cord has been identified, suggesting that these repellents do not control anterior-posterior pathfinding.

However, a role for Wnts in mammalian directional axonal growth regulation in the spinal cord has not previously been suggested or considered.

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