Identification of endogenous migratory MSC-like cells and their interaction with the implant materials guiding osteochondral defect repair

In this work, spindle-shaped cells derived from bone marrow were separated from the regenerated tissue of an osteochondral defect in a SD rat model. These cells were defined as MSC-like cells because they revealed similar features with MSCs, as demonstrated by the cell morphological observation, H&E staining of the regenerated tissue, typical MSC surface markers, and the differentiation potential assays in osteogenesis, adipogenesis, and chondrogenesis. Bioinert agarose and bioactive collagen I hydrogels were filled in the osteochondral defects to investigate the effects of different biomaterials on the MSC-like cell migration, differentiation, and osteochondral regeneration. After one month's surgery, the defect site was evaluated by histologic staining, IHC staining and micro-CT. These results indicated that the bioinert agarose significantly inhibited cell migration and tissue regeneration, while the bioactive collagen I hydrogel was found to have a therapeutic effect. It would be tempting to speculate that the specifically designed scaffolds that facilitated cell migration were more propitious to osteochondral defect healing. The migration of the MSC-like cells into the osteochondral defect had produced promising outcomes and showed therapeutic potency. In the future, additional work will focus on elucidating the sophisticated mechanisms underlying the origin of the MSC-like cells, function and consequences of cell migration to understand the treatment of osteochondral defects.