Neutralizing the degenerate disc microenvironment to enhance the efficacy of therapeutic stem cells

Abstract Low back pain is the leading cause of disability in the United States, with an estimated socioeconomic cost exceeding $100 billion each year. Intervertebral disc degeneration, a cascade of cellular, compositional, structural and compositional changes, is strongly implicated as a cause of low back pain. Current clinical approaches for treating low back pain associated with disc degeneration have limited long term efficacy as they seek only to manage symptoms without restoring native disc structure and mechanical function. There is an overwhelming clinical need for new treatment options, which target not only the symptoms of low back pain, but also the underlying causes. Mesenchymal stem cells (MSCs) are an attractive option for cell- based disc regeneration due to their safety, ease of isolation and ability to adopt phenotypes similar to those of disc nucleus pulposus cells. A major challenge to successful MSC-based disc regeneration, however, is the local cellular microenvironment, which presents conditions of limited nutrition, low oxygen, low pH, and persistent inflammation that predispose therapeutic interventions to failure. The objective of this proposal is to develop a novel biological therapy that maximizes the survival and anabolic potential of therapeutic stem cells by simultaneously neutralizing the degenerate disc microenvironment via the sustained delivery of nutrients, anti-inflammatory drugs and buffering agents. To accomplish this goal, we will leverage our newly established goat model of disc degeneration that mimics clinically relevant structural, composition and biomechanical characteristics, including tissue-level inflammation, and novel drug delivery methods to enable controlled and sustained release of biofactors that neutralize the degenerative microenvironment. In Aim 1 we will leverage our goat model define the in vivo cellular microenvironment of the disc as a function of degeneration severity, using cutting edge in situ physiological monitoring and ex vivo biomolecular assays. In Aim 2 we will optimize our novel microcapsule drug delivery system to neutralize the degenerate disc microenvironment through sustained delivery of glucose, anti- inflammatory drugs and buffering agents. In Aim 3 we will carry out short and long term in vivo studies to establish therapeutic efficacy in our goat model, including clinically-relevant pain assessments. At the conclusion of these studies we will have developed a rapidly translatable therapy that maximizes the regenerative potential of MSCs in the disc microenvironment, and established long term preclinical efficacy, thus placing us in a strong position to move towards human clinical trials.