[Experimental study of repairing femoral bone defects with nHA/RHLC/PLA scaffold composite with endothelial cells and osteoblasts in canines].

OBJECTIVE: To explore whether a tissue-engineered construct composed of autogenous endothelial cells, osteoblasts and a new bioresorbable nano-hydroxyapatite/recombinant human-like collagen/polylactic acid (nHA/RHLC/PLA) would enhance bone regeneration and repair femoral head defects in canine models.

METHODS: The bone marrow stem cells (BMSCs) were isolated from bone marrow of canine ilium and cultured in Dulbecco's modified eagle medium:nutrient mixture F-12 culture media for 1 week and the second-generation BMSCs were further induced by osteogenic medium (1×10(-8) mol/L dexamethasone, 10 mmol/L B-sodium glycerophosphate and 50 µg/ml vitamin C) and by endothelial cell grow medium (vascular endothelial growth factor and basic fibroblast growth factor) for 14 days in vitro. Thus BMSCs were induced into ECs and OBs. After the second passage, cells were digested and collected.And cell density was adjusted to 1.0×10(6)/ml.The cells and nHA/RHLC/PLA scaffold were co-cultured for 2-4 hours then nHA/RHLC/PLA scaffold composites prepared. Cavity defects of 8 mm in diameter and 10 mm in height were made in femoral heads.The nHA/RHLC/PLA scaffold composited with ECs and osteoblasts (OBs) (group A) and composited with OBs (group B) were inserted into different defects while cell-free nHA/RHLC/PLA scaffold served as controls (group C). New bone formation and defect repair were evaluated at 3 and 6 months by radiographic examination, histology and bone histomorphometry.

RESULTS: New bone formation was evident as early as 3 months in groups A, B and C.At 6 months, abundant bone tissue within defects was observed in group A. The control animals with cell-free scaffold showed less bone formation at both timepoints.The scaffold of nHA/RHLC/PLA was degraded and absorbed gradually with the formation of new bone tissues.Histology and bone histomorphometry further revealed significantly increased trabecular bones in group A compared with groups B and C at 6 months postimplantation (P < 0.01).

CONCLUSION: More abundant new bone tissue may be found in the bone defect areas implanted with osteoblast-endotheliocyte composite than osteoblasts composite and scaffold materials only.ECs and osteoblasts derived from BMSC are ideal seed cells for repairing femoral head defects.