Recombinant human bone morphogenetic protein-7 enhances bone formation ability of jaw bone defect using human umbilical cord mesenchymal stem cells combined with nano-hydroxyapatite/collagen/poly(L-lactide)

Abstract Background: Human umbilical cord mesenchymal stem cells (hUC-MSCs) have been suggested as an alternative source of MSCs. However, the studies on its bone formation ability in oral maxillo-facial bone defect are rare. This study investigated the bone formation ability of recombinant human bone morphogenetic protein-7 (rhBMP-7)-induced hUC-MSCs combined with nano-hydroxyapatite/collagen/poly(L-lactide) (nHAC/PLA) in the back of nude mice and jaw bone defect of rabbit. Methods: The characteristics of hUC-MSCs were analyzed by plastic adherence, cell phenotype and multilineage differentiation potential. Cell proliferation was examined using a CCK-8 assay. Osteogenic differentiation was evaluated by quantitative calcium concentration, phosphorous concentration, alkaline phosphatase (ALP) activity, osteocalcin (OCN) concentration, mineral formation, and the mRNA levels of ALP, OCN and bone morphogenetic protein (BMP)-2. Scanning electron microscopy was used to observe cell adhesion, growth and differentiation. Bone formation was assessed by immunohistochemical staining, micro-CT and hematoxylin and eosin staining. Results: The isolated hUC-MSCs expressed CD105, CD90 and CD73, did not express CD45, CD34, CD11a and HLA-DR, exhibited self-renewal potential, and favored osteogenesis and adipogenesis. The exogenously-added rhBMP-7 attenuated the inhibitory effect of the serum-free osteogenic media (OMD) on the proliferation of hUC-MSCs combined with nHAC/PLA, increased the promoting effect of OMD on osteogenic differentiation of hUC-MSCs in two or three-dimensional culture, and enhanced its heterotopic bone formation and jaw bone defect repair abilities. Furthermore, the bone formation of in situ bone defect was significantly superior to heterotopic bone formation. Conclusions: That the microenvironment formed by the regenerative engineered constructs and the in situ bone defect microenvironment closely matched that of the bone tissue in its native state may be essential for sufficient and timely bone regeneration. The endogenously-produced BMPs may serve an important regulatory role in the process. These results paved the way for developing allogeneic hUC-MSCs-based constructs for clinical jaw bone regenerative therapeutic applications.