Collagen-hydroxyapatite microspheres as carriers for bone morphogenic protein-4.

The purpose of the current study is to evaluate the carrier capability of collagen-hydroxyapatite microspheres to the bone morphogenic proteins (BMP). After anesthesia, a bone defect (6.0 mm in diameter and 10.0 mm in depth) was created at the distal femoral condyles of New Zealand white rabbits. These 10.0 mm3 defects were then completely filled with the implant materials. After 2, 4, 6, and 8 weeks, the animals were sacrificed and histological evaluations were performed. The results showed that when the defects were left untreated, there was no evidence of bone formation during the eight-week experimental period. In the group treated with collagen-hydroxyapatite microspheres without BMP-4, the defect was filled with fibrous tissue and inflammatory cells, while active bone formation with mature marrow tissue formation was evident in the defect treated with collagen-hydroxyapatite microspheres containing BMP-4. Collagen-hydroxyapatite microspheres were expected to be replaced by the regenerated bone structure as the bone reconstruction and bone remodelling process occurred. It was apparent that bone regeneration was influenced by the addition of BMP-4. Collagen-hydroxyapatite microspheres were good carriers for bone morphogenic proteins.