Stem cells, scaffolds and small molecules for orthopedic tissue regeneration
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Orthopedic tissue regeneration would benefit the aging population or patients with large osteoporotic large bone fracture and degenerative cartilage diseases, especially osteoarthritis (OA). Despite progress in surgical and pharmacological interventions, new regenerative approaches are needed to meet the challenge of restoring bone and articular cartilage tissues that are not only structurally sound but also functional. The following work explores two promising therapeutic strategies for orthopedic tissue regeneration: “ex vivo tissue engineering” to engineer bone tissue constructs with smart combinations of stem cells and biomaterials and “small molecule-based in vivo regenerative approach” to i) promote the chondrogenic potential of endogenous progenitor cells and ii) eliminate abnormal cells – senescent cells (SnCs) – that develop with OA. The ex vivo tissue engineering focused on the development of functional bone like-tissue by co-culturing human induced pluripotent stem cells-derived osteoblasts (OB) and osteoclasts (OC) in hydroxyapatite (HA)-based three dimensional scaffolds. Results showed 3D bone model comprising both cell types promote bone formation compared to OB only cultures in a HA-dose dependent manner via coupling signals coordinating osteoblast and osteoclast activity and finely tuned expression of inflammatory molecules. The first small molecule approach for cartilage regeneration that was explored involved carbohydrate-based OA drug, tri-butanoylated N-acetyl-D-galactosamine analog, as a inducer of chondrogenic differentiation of hMSCs and inhibitor of inflammation. The second drug-based therapy is intra-articular (IA) injection of a senolytic molecule that selectively killed SnCs. This work explores the role of SnCs in the disease progression of post-traumatic and naturally-occurring OA and how eliminating SnCs can slow OA development. It was found SnCs accumulate in the articular cartilage after anterior cruciate ligament transection (ACLT) and selective elimination of these cells attenuated the development of OA, reduced pain, and increased cartilage development. The three therapies presented in this dissertation represent viable strategies for bone and articular cartilage regeneration.