Figure 1. Overview of the multistep approach used to develop an in vitro model of osteoarthritis (OA) using cartilage derived from murine iPSCs.
iPSCs were first differentiated in micromasses and then purified based on a collagen type II-GFP reporter. Purified cells were expanded and then cultured as pellets to produce a robust cartilaginous matrix. As a model of OA, iPSC-derived cartilage was cultured with interleukin-1α to create a reproducible degenerative response. Native mouse cartilage served as a control to ensure that the breakdown of iPSC cartilage was consistent with an OA phenotype. After validating the model, pellet formation, culture, and analyses were adapted to a 96-well plate system so that candidate OA therapeutics could be screened efficiently. CM: chondrogenic medium, BMP-4: bone morphogenetic protein 4, bFGF: basic fibroblastic growth factor, TGF-β3: transforming growth factor beta 3, dex: dexamethasone.