The Role of Mesenchymal Stem Cell Therapy for Disc Degeneration
Low-back pain is the most common health problem for men and women between 20 and 50 years of age, resulting in 13 million doctor visits in the US annually, with significant costs to society in terms of lost time from work and direct and indirect medical expenses. Although the exact origin of most cases of low-back pain remains unknown, it is understood that degenerative damage to the intervertebral disc (IVD) plays a central role in the pathogenic mechanism leading to this disorder. Current treatment modalities for disc-related back pain (selective nerve root blocks, surgical discectomy and fusion) are costly procedures aimed only at alleviating symptoms. Consequently, there is growing interest in the development of novel technologies to repair or regenerate the degenerated IVD. Recently, mesenchymal stem cells (MSCs) have been found to possess the capacity to differentiate into nucleus pulposus–like cells capable of synthesizing a physiological, proteoglycan-rich extracellular matrix characteristic of healthy IVDs. In this article, the authors review the use of MSCs for repopulation of the degenerating IVD. Although important obstacles to the survival and proliferation of stem cells within the degenerating disc need to be overcome, the potential for MSC therapy to slow or reverse the degenerative process remains substantial.

Back pain is a cause of significant morbidity in all Western industrialized societies. It is estimated that up to 80% of the population in these societies will experience some form of back pain over their lifetime, with approximately 10% of sufferers becoming chronically disabled. Not only does this result in a significant amount of physical and emotional distress for patients and their families, but it is also an enormous economic burden. The societal costs for medical treatment, lost time from work, and disability benefits are on the order of $30 billion annually in the US alone, and £12 billion per year in the United Kingdom.

Although there are numerous causes of back pain, it is clear that this disorder is strongly associated with degeneration of the IVD. Moreover, IVD degeneration is thought to contribute to spinal arthritis, radiculopathy, and myelopathy. Instead of focusing on repairing or reversing damage to the IVD, current treatment strategies, including nonsurgical (physical therapy, nerve root blocks) and surgical ones (disc excision and arthrodesis) effect only symptomatic relief and may actually accelerate the same degenerative process at adjacent levels. Thus, degeneration of the IVD is currently regarded as an irreversible phenomenon with no effective treatment. Nevertheless, recent advancements in the understanding of tissue repair mechanisms and stem cell biology have led to the identification of novel tissue engineering–based treatment strategies to regenerate or repopulate the diseased IVD with stem cells.

In this paper we comment on the ability of MSCs to slow or reverse the degenerative process, on potential obstacles to stem cell survival and proliferation within the degenerating disc, and we conclude with future directions for research aimed at overcoming these barriers.