Tuning the Delivery and Response of Injectable Stem Cells for Cartilage Repair

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My professional aspiration is to develop an independent research career exploring innovative implants and therapeutics for musculoskeletal tissue repair and regeneration. During my graduate studies at Rutgers University, I designed and fabricated a novel fiber-reinforced meniscus scaffold, evaluated it in a long-term large animal model, and tested its implantation and load-bearing efficacy in human cadaveric knees. With this productive graduate career involving macro-scale biomechanics and tissue engineering, I was fortunate to join the CMCVAMC and the University of Pennsylvania for my postdoctoral training, under the mentorship Dr. Robert Mauck, in order to gain experience and knowledge in cell-biomaterial interactions, mechano-biology, and tissue engineering at the micro-scale. Furthermore, a seasoned co-mentoring team will provide significant support with regards to biomaterials synthesis and modification, surgical models and approaches, and clinical translation. The proposed research plan will expose me to these concepts and methods that work complimentarily to my current skillset, and uses these micro-scale approaches to inform a macro-scale therapy for cartilage defects. Articular cartilage is a remarkable tissue, with a dense extracellular matrix that allows the tissue to undergo fluid pressurization during compressive loading. Cartilage defects compromise this function, introducing free boundaries that result in the flow of proteoglycans and other matrix elements out of the tissue. Decreases in matrix density at defect boundaries make them vulnerable to progressive erosion, instigating a vicious cycle that gradually increases defect size and concludes with joint-wide osteoarthritis (OA). The development of a therapeutic to delay or prevent this progression would be groundbreaking in the clinical management of cartilage injuries. To address cartilage defects, various repair and regeneration techniques have been developed, yet most are inconsistent or ineffective. While new and modified biomaterials can improve treatment efficacy by targeting damaged cartilage to improve scaffold integration or biofactor delivery, the use of such molecular targeting to functionally restore the mechanical properties of the defect boundary has not yet been investigated. We hypothesize that, by introducing a living fibrous barrier that limits fluid flow through the interface (via targeted progenitor cell recruitment and differentiation), one might reestablish normal cartilage biomechanical function and therefore preserve cartilage in the vicinity of a defect, stemming OA progression. To test this hypothesis, the objective of this proposal is to target damaged cartilage with a tunable microenvironment that can recruit cells and direct their activities towards the formation of a barrier that will restore and preserve the native cartilage mechanical function and matrix content. Specifically, we will (1) develop a biomaterial that can effectively localize to defected cartilage; (2) tune the biomolecular and biomechanical cues to attract cells and promote formation of a fibrous barrier; and (3) evaluate the ability of this living barrier to restore fluid pressurization capacity and prevent proteoglycan loss after injury. The first undertaking will be accomplished by optimizing the delivery of modified hyaluronic acid to damaged cartilage, while maintaining native cell cytocompatibility. Next, the delivered biomaterial will be modified to maximize cell attachment and spreading, two requirements for fibrous tissue deposition. Lastly, the efficacy of the microenvironment in delaying progressive matrix loss from defect boundaries will be determined in both an in vitro cartilage explant culture model, and in a large-animal cartilage defect model. A therapeutic that produces a living low-permeability tissue barrier has the potential to delay or prevent the growth of focal defects into joint- wide OA. The proposed research plan and outstanding institutional environment will provide me with the necessary skills and experiences to become a successful VA-based independent investigator.