A Novel Injectable Cell-Loaded Hydrogel System for Cartilage Repair: <i>In Vivo</i> and <i>In Vitro</i> Study

Polyhydroxyalkanoates are promising biomaterials, but their application in cartilage repair is still limited. In this study, an injectable thermosensitive hydrogel poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate)-Polyethylene Glycol (PEG)/hyaluronic acid/kartogenin was prepared from 3-hydroxybutyrate, 3-hydroxyvalerate, 3-hydroxyhexanoate, hyaluronic acid, and kartogenin. The hydrogels are porous, temperature-sensitive, and hydrophilic and have good compressive modulus. Mesenchymal stem cells derived from peripheral blood can proliferate on the hydrogels under two- and three-dimensional cultures. In addition, the hydrogel has the ability to induce chondrogenic differentiation of stem cells and induce M2 differentiation of macrophages. The hydrogel loaded with peripheral blood mesenchymal stem cells can repair cartilage defects in the knee joints of New Zealand rabbits and the newly formed cartilage was identified as type II collagen. Overall, this newly developed system could provide a new treatment option for repairing cartilage defects.