Delivery of dimethyloxalylglycine in calcined bone calcium scaffold to improve osteogenic differentiation and bone repair.

As hypoxia plays a vital role in the angiogenic-osteogenic coupling, using proline hydroxylase inhibitors to manipulate hypoxia-inducible factors has become a strategy to improve the osteogenic properties of biomaterials. Dimethyloxallyl glycine (DMOG) is a 2-ketoglutarate analog, a small molecular compound that competes for 2-ketoglutaric acid to inhibit proline hydroxylase. In order to improve the osteogenic ability of calcined bone calcium (CBC), a new hypoxia-mimicking scaffold (DMOG/Collagen/CBC) was prepared by immersing it in the DMOG-Collagen solution, followed by freeze-drying. All coated CBC scaffolds retained the inherent natural porous architecture and showed excellent biocompatibility. A slow release of DMOG by the DMOG-loaded CBC scaffolds for up to one week was observed in in vitro experiments. Moreover, the DMOG/Collagen/CBC composite scaffold was found to significantly stimulate bone marrow stromal cells to express osteogenic and angiogenic genes in vitro. In addition, the osteogenic properties of three kinds of scaffolds, raw CBC, Collagen/CBC, and DMOG/Collagen/CBC, were evaluated by histology using the rabbit femoral condyle defect model. Histomorphometric analyses showed that the newly formed bone (BV/TV) in the DMOG/Collagen/CBC group was significantly higher than that of the Collagen/CBC group. However, immunostaining of CD31 and Runx2 expression between these two groups showed no significant difference at this time point. Our results indicate that DMOG-coated CBC can promote osteogenic differentiation and bone healing, and show potential for clinical application in bone tissue engineering.