Overall Research Strategy: The overall goal of the CaRa-AP Collaborative Program is to develop a treatment for post-traumatic osteoarthritis (PTOA) that will relieve pain and improve function. We hypothesize that PTOA is caused by maladaptive repair responses including activation of the pro-inflammatory pathways of innate immunity that in turn result in pain, loss of function and structural decline. This Program addresses the hypothesis through two highly-integrated aims: (1) innovative intra-articular treatments using small molecules, biologic inhibitors and immunomodulatory cells to reduce pain and inflammation in the joint and (2) tissue engineering using stem cell-based therapies for reconstruction of the damaged joint infrastructure. The investigators collaborating in this program will coordinate testing of therapies in four animal models that mimic different mechanisms of injury that initiate PTOA in patients. The experiments will take into consideration relevant factors affecting joint physiology and treatment response. The effects of different therapeutic modalities will be evaluated using group-standardized measurements of pain, function, inflammation and structure, so that results can be compared across laboratories and the most promising therapeutic strategies prioritized for clinical trials. We provide compelling evidence that sequential treatment of mesenchymal progenitors with BMP2 and non- canonical Wnt5a, cultured in high density pellets, yield articular-like cells in vitro. These effects are reproduced when small molecules Kartogenin (KGN), a chondrogenic small molecule targeting Runx1, and Foxy5, a Wnt5a mimetic peptide, are sequentially used. Moreover, implantation of pellets, treated with BMP2 followed by Wnt5a, into a rat chondral defect regenerate articular-like cartilage. Our preliminary data also demonstrate an influence of physical exercise on cartilage preservation and joint function in a rat model of PTOA. Thus, we ask whether the source of stem cells can differentially promote hyaline cartilage regeneration and if physical rehabilitation can improve pellet integration and treatment outcome. Specifically, we aim to compare the efficacy of somatic cells (human articular chondrocytes and bone marrow derived mesenchymal stem cells) to that of patient- specific, and readily available, pluripotent stem cells. We hypothesize that cell plasticity will determine the potential of adult versus pluripotent stem cells to treat cartilage degeneration, and that successful restoration of cartilage integrity via cellular and physical therapy will lead to enhanced functional outcomes and reduced nociception in vivo. We will first establish the capacity of iPSC-derived MSCs to that of adipose-derived and human articular cartilage MSCs with and without sequential treatment with KGN and Foxy5 to regenerate articular cartilage following implantation of control or treated high-density pellets into a rat chondral defect model of PTOA. Histological evaluations, matrix synthesis, mechanical testing and molecular imaging analyses will be performed (Aim 1). We will then assess the effect of cellular and physical treatment of animals on long-term functional, nociceptive, and centralized pain outcomes. We will evaluate functional outcomes in control and experimental rats that receive either iPSC-derived MSCs or the most effective adult stem cell source identified in Aim 1. Specifically, gait, voluntary running, muscle strength, mechanical testing, and allodynia analyses will also be performed. We will also assess the neurological changes that often lead to chronic joint pain (Aim 2).
A staggering 94.4% of our young veterans returning from the Global War on Terror with fragment projectiles and gunshot wounds will develop arthritis, presenting a serious need to regenerate permanent cartilage of their joints before the development of osteoarthritis and a lifetime of pain. This proposal builds upon our recently developed stem cell-based strategy of tissue regeneration by establishing the efficacy of readily available cell sources and physical therapy to repair articular cartilage defects, restore joint function, and alleviate pain. We believe our approach will ultimately circumvent a variety of limitations and move us towards an off-the-shelf solution to post-traumatic osteoarthritis.
