Differentiation of osteoblast-like cells and ectopic bone formation induced by bone marrow stem cells transfected with chitosan nanoparticles containing plasmid-BMP2 sequences

The present study investigated the efficiency of the use of chitosan nanoparticles containing plasmid‑bone morphogenetic protein 2 (pBMP2) sequences (CNPBs) to induce the differentiation of bone marrow stem cells (BMSCs) into osteoblast‑like cells that may be able to promote ectopic bone formation. pBMP2s were constructed, and chitosan nanoparticles were incubated with 50, 100 or 200 µg/ml pBMP2. BMSCs were collected from the tibiae and femurs of 6‑week old rats, cultured and treated with the CNPBs or 200 µg/ml pBMP2 as a positive control. Transfection efficiency was confirmed using the green fluorescent protein assay. Histological staining methods, including alkaline phosphatase, Wright's and von Kasso staining, were used to identify features of osteoblast‑like cells differentiated from BMSCs. Expression levels of the markers of osteoblasts, such as alkaline phosphatase, osteoprotegerin, osteocalcin and osteopontin, were determined to verify the differentiation of BMSCs into osteoblast‑like cells. Ectopic bone formation was observed following the integration of polyglycolic acid (PGA) scaffolds with CNPBs and BMSCs, which were implanted into the dorsal muscles of Sprague‑Dawley rats. Exposure to CNPBs led to the transfection of BMSCs with BMP2. The transfected BMSCs possessed the characteristic phenotypes of osteoblasts. The expression levels of alkaline phosphatase, osteoprotegerin, osteocalcin and osteopontin were significantly higher in the transfected cells compared with the control group, particularly the CBP200 group. PGA scaffolds integrated with BMSCs and CNPBs induced ectopic bone formation, as changes in the morphology of cells were observed using histological staining. Therefore, CNPBs may be a promising method of promoting the formation of novel bone tissue.