Integrated Multi-Assay Culture Model for Stem Cell Chondrogenic Differentiation

Recent osteochondral repair strategies highlight the promise of mesenchymal progenitors, an accessible stem cell source with osteogenic and chondrogenic potential, used in conjunction with biomaterials for tissue engineering. For this, regenerative medicine approaches require robust models to ensure selected cell populations can generate the desired cell type in a reproducible and measurable manner. Techniques for in vitro chondrogenic differentiation are well-established but largely qualitative, relying on sample staining and imaging. To facilitate the in vitro screening of pro-chondrogenic treatments, a 3D micropellet culture combined with three quantitative GAG assays has been developed, with a fourth parallel assay measuring sample content to enable normalisation. The effect of transforming growth factor beta (TGF-β) used to validate this culture format produced a measurable increase in proteoglycan production in the parallel assays, in both 2D and 3D culture configurations. When compared to traditional micropellets, the monolayer format appeared less able to detect changes in cell differentiation, however in-well 3D cultures displayed a significant differential response. Effects on collagen 2 expression confirmed these observations. Based on these results, a microplate format was optimised for 3D culture, in a high-throughput in-well configuration. This model showed improved sensitivity and confirmed the 3D micropellet in-well quantitative assays as an effective differentiation format compatible with streamlined, high-throughput chondrogenic screens.