Cell-derived matrix enhances osteogenic properties of hydroxyapatite

The study aimed to evaluate osteogenic properties of hydroxyapatite (HA) scaffold combined with extracellular matrix (ECM) derived in vitro from rat primary calvarial osteoblasts or dermal fibroblasts. The cellular viability, and the ECM deposited onto synthetic HA microparticles were assessed by MTT, Glycosaminoglycan, and Hydroxyproline assays as well as immunohistochemistry and scanning electron microscopy after 21 days of culture. The decellularized HA-ECM constructs were implanted in critical-sized calvarial defects of Sprague-Dawley rats, followed by bone repair and local inflammatory response assessments by histomorphometry and immunohistochemistry at 12 weeks postoperatively. We demonstrated that HA supported cellular adhesion, growth, and ECM production in vitro, and the HA-ECM constructs significantly enhanced calvarial bone repair (p<0.05, Mann-Whitney U-test), compared with HA alone, despite the significantly increased number of CD68+ macrophages, and foreign body giant cells (p<0.05, Mann-Whitney U-test). Selective accumulation of bone sialoprotein, osteopontin, and periostin was observed at the tissue-HA interfaces. In conclusion, in vitro-derived ECM mimics the native bone matrix, enhances the osteogenic properties of the HA microparticles, and might modulate the local inflammatory response in a bone repair-favorable way. Our findings highlight the ability to produce functional HA-ECM constructs for bone tissue engineering applications.