Ectopic osteogenesis induced by microspheres of chiston/dextran sulfate/recombinant human bone morphogenetic protein-2

Abstract

Objective To explore the capacity of microspheres of chiston/dextran sulfate/recom-binant human bone morphogenetic protein-2 (CS/DS/rhBMP-2) to induce ectopic osteogenesis. Methods Quadriceps muscle bags were created at the left legs in 48 SD rats which were randomly divided into 4 groups. Gelatin sponge, CS/DS, rhBMP-2 and CS/DS/rhBMP-2 microspheres were implanted into the muscle bags of the 4 groups respectively. At 4, 8, 12 and 16 weeks after implantation, samples were har-vested for examinations of histology by hematoxylin-eosin (HE) staining, alkaline phosphatase (ALP) activity and calcium content. An X-ray check was done at the 16th weekend. Results At 4 weeks, no obvious bone tissue formed in the 4 groups. At 8 weeks, in CS/DS/rhBMP-2 group, a small number of bone cells were observed, bone marrow formed, trabecular bone turned into mature sclerotin, and bone marrow and bone-like materials formed between the trabecular bones. In rhBMP-2 group, some trabecular bone and bone cells were seen, there were a small number of osteoblasts and chondrocytes around the bone cells, but the bone tissues were less mature than in CS/DS/rhBMP-2 group. At 12 and 16 weeks in CS/DS/rhBMP-2 and rhBMP-2 groups, mature bone tissues were seen, and on bone pits in trabecular bone there were bone cells around which a large number of osteoblasts appeared. The bone tissues in CS/DS/rhBMP-2 group were more mature than in rhBMP-2 group, and there were more bone lacunas and bone trabeculae in CS/DS/rhBMP-2 group. No obvious bone tissues formed in gelatin sponge or CS/DS groups. At 8, 12 and 16 weeks, the ALP activity and calcium content in CS/DS/rhBMP-2 group were significantly higher than in rhBMP-2 group (P<0.05). X-ray check at 16 weeks revealed radio-opaque substance with uniform density at the implantation sites in both CS/DS/rhBMP-2 and rhBMP-2 groups. The radiation density of CS/DS/rhBMP-2 microspheres was close to that of nearby femur while the radiation density of rhBMP-2 microspheres was lower than that of nearby femur. The high density radiation area in CS/DS/rhBMP-2 group was larger than in rhBMP-2 group. No high density tissues formed in gelatin sponge or CS/DS group. Conclusion Since CS/DS/rhBMP-2 microspheres are more capable of inducing ectopic bone formation than rhBPM-2 ones, they may have a promising prospect of application in bone tissue engineering. Key words: Bone morphogenetic proteins; Chitosan; Dextran sulfate; Ossification, hetero-topic