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<p><p> Articular cartilage is a smooth connective tissue that covers the ends of bones
and protects joints from wear. Cartilage has a poor healing capacity, and the lack
of treatment options motivates the development of tissue engineering strategies.
The widespread cartilage degeneration associated with osteoarthritis (OA) is dramatically
accelerated by joint injury, but the defined initiating event presents a therapeutic
window for preventive treatments. In vitro model systems allow investigation of OA
risk factors and screening of potential therapeutics. This dissertation develops
stem-cell based strategies to 1) treat cartilage injury and OA using tissue-engineered
cartilage, 2) prevent the development of OA by delivering stem cells to the joint
after injury, and 3) study cartilage by establishing systems to model genetic and
environmental contributors to OA.</p><p> Adipose-derived stem cells (ASCs) and bone
marrow-derived mesenchymal stem cells (MSCs) are promising human adult cell sources
for cartilage tissue engineering, but require distinct chondrogenic conditions. As
compared to ASCs, MSCs demonstrated enhanced chondrogenesis in both alginate beads
and cartilage-derived matrix scaffolds. </p><p> We hypothesized that MSC therapy would
prevent post-traumatic arthritis (PTA) by altering the balance of inflammation and
regeneration. Highly purified MSCs (CD45-TER119-PDGFRα+Sca-1+) rapidly expanded
under hypoxic conditions. Unexpectedly, MSCs from control C57BL/6 (B6) mice proliferated
and differentiated more than MSCs from MRL/MpJ (MRL) "superhealer" mice. We injected
B6 or MRL MSCs into mouse knees immediately after fracture, and MSCs of either strain
were sufficient to prevent PTA. </p><p> Genetically reprogramming adult cells into
induced pluripotent stem cells (iPSCs) generates large numbers of patient-matched
cells with chondrogenic potential for therapy and cartilage modeling. We produced
murine iPSC-derived cartilage constructs with a multi-phase approach involving micromass
culture with bone morphogenetic protein-4, flow cytometry cell sorting of chondrocyte-like
cells, monolayer expansion, and pellet culture with transforming growth factor-beta
3. Successful differentiation was confirmed by increased chondrogenic gene expression,
robust synthesis of glycosaminoglycans and type II collagen, and the repair of an
in vitro cartilage defect. </p><p> The diverse applications pursued in this research
illustrate the power of stem cells to deepen the understanding of cartilage and guide
the development of therapies to prevent and treat cartilage injury and OA.</p>
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