Methods and compositions for diagnosing and treating arthritic disorders and regulating bone mass

Abstract

The present invention relates to improved diagnostic methods for early detection of a risk for developing an arthritic disorder in humans, and screening assays for therapeutic agents useful in the treatment of arthritic disorders, by comparing the levels of one or more indicators of altered mitochondrial function. Indicators of altered mitochondrial function include enzymes such as mitochondrial enzymes and ATP biosynthesis factors. Other indicators of altered mitochondrial function include mitochondrial mass, mitochondrial number and mitochondrial DNA content, cellular responses to elevated intracellular calcium and to apoptogens, and free radical production. Methods of treating, and of stratifying, human patients as such methods relate to disclosed indicators of altered mitchondrial function are also provided.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 09 / 661,848, filed Sep. 14, 2000, and claims the benefit of U.S. Provisional Patent Application No. 60 / 154,145 filed Sep. 15, 1999, which applications are incorporated herein by reference in their entireties.STATEMENT OF POTENTIAL GOVERNMENT RIGHTS IN THE INVENTION [0002] Part of the invention was made in the course of research sponsored by NIH grant number P01AG07996 and by a Merit Review Award from the Veterans Affairs Medical Service to one of the inventors (R.T.). The United States Government may have certain rights in this invention.TECHNICAL FIELD [0003] The present invention relates generally to arthritis and related disorders. In particular, the invention relates to compositions and methods for the diagnosis, prognosis and treatment of osteoarthritis and rheumatoid arthritis, and for preventing bone loss. BACKGROUND OF THE INVENTION [0004] Numerous chronic deb...

AI Technical Summary

Benefits of technology

The present invention provides a method for identifying a risk for arthritic disorders in a vertebrate subject by comparing the level of at least one indicator of altered mitochondrial function in a biological sample from the subject with a control sample. The method can also be used to determine the degree of progression of the arthritic disorder by comparing the level of the indicator at different time points. Additionally, the invention provides a method for identifying an agent suitable for treating a vertebrate subject suspected of having an arthritic disorder by comparing the level of the indicator before and after administering the agent to the subject. The invention can also be used to identify subtypes of arthritic disorders in a vertebrate species.

Problems solved by technology

Severe breakdown of the joint cartilage by biochemical and / or biomechanical processes leads to arthritis, which is therefore generally defined as a failure of the vertebrate weight bearing system.

Impaired skeletal joint function dramatically reduces an individual subject's mobility, such as that involved in rising from a sitting position or in climbing and descending stairs.

Lack of these precursors will lead to defects in the structure and function of the skeletal joints.

This deficiency occurs often when activity levels are very high, or when cartilage tissue is traumatized.

Damage to these structures can lead to impaired joint function and to articular cartilage degeneration.

Surgical removal of these fibrocartilagenous structures, for example, following apparently irreparable cartilage tears, can result in early onset of osteoarthritis.

These joints typically perform their functions so well and efficiently that their existence may be innocuous until injury strikes or arthritis develops.

Failure of the joint bearings surfaces (i.e., articular cartilage), as with mechanically engineered artificial bearings, means a failure of these bearings to provide their central functions, such as delivery of mechanical energy and load support.

In extreme cases, chronic inflammation erodes and distorts the joint surfaces and connective tissue, resulting in severe articular deformity and constant pain.

Moreover, RA often leads to OA, further compounding the destruction of the joint.

Finally, complete erosion occurs, leaving the subchondral bone exposed and susceptible to wear.

In both RA and OA, degeneration of the weight bearing joints such as the hips and knees can be especially debilitating and often requires surgery to relieve pain and increase mobility.

No means currently exist for halting or reversing the degenerative changes brought about by RA and related arthritic disorders.

While these compounds often alleviate or palliate the arthritic symptoms, they frequently have undesirable side effects, for example, nausea and gastrointestinal ulceration.

These drugs also have undesirable side effects, particularly where long term use may be required, and so may be contraindicated in many patients.

In addition to difficulties in determining effective dosages, a number of adverse reactions have been reported during intra-articular treatment with these and other steroids.

With more than thirty million Americans suffering from these disabling diseases, such surgery poses enormous medical and economic challenges and is not without its own risks and contraindications.

It is characterized by the breakdown of the cartilage within a joint, causing painful rubbing of one bone of the joint against another bone and leading to a loss of movement within the affected joint.

Included in the more than 80 affected canine breeds are German shepherd, Newfoundland, Old English sheepdog, English bulldog, Labrador retriever, other retriever breeds, Irish setter, Great Dane, and St. Bernard. The disease is characterized by laxity and incongruity of the hip joint, which results in degeneration of joint tissues.

Osteoarthritis develops as a result of the abnormal positioning of the head of the femur in relation to the joint due to laxity, and results in the erosion of joint cartilage, and inflammation of the synovium.

However, a problem arises in that the outcome for Labradors having a distraction index in this range cannot reliably be predicted (Smith et al., 1993, supra; Lust et al., 1993 Am. J. Vet. Res.

Altered or defective mitochondrial activity, including but not limited to failure at any step of the ETC, may result in catastrophic mitochondrial collapse that has been termed “permeability transition” (PT) or “mitochondrial permeability transition” (MPT).

Altered or defective mitochondrial activity may dissipate this membrane potential, thereby preventing ATP biosynthesis and halting the production of a vital biochemical energy source.

When, however, the integrity of the inner mitochondrial membrane is compromised, as occurs during MPT that may accompany a disease associated with altered mitochondrial function, protons are able to bypass the conduit of Complex V without generating ATP, thereby “uncoupling” respiration because electron transfer and associated proton pumping yields no ATP.

Moreover, some disease states are thought to be associated with either insufficient (e.g., cancer, autoimmune diseases) or excessive (e.g., stroke damage, AD-associated neurodegeneration) levels of apoptosis.

Neither do any of these currently available treatments improve all of the physiological abnormalities in arthritic disorders such as abnormal articular chondrocyte activity, cartilage degradation, articular erosion and severe joint deformity.

In addition, treatment failures are common with these agents, such that multi-drug therapy is frequently necessary.

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