[Promoting of angiogenesis and osteogenesis in radial critical bone defect regions of rabbits with nano-hydroxyapatite/collagen/PLA scaffolds plus endothelial progenitor cells].

Objective To explore the roles of nano-hydroxyapatite/collagen/PLA (nHAC/PLA)plus endothelial progenitor cells (EPCs) in repairing segmental bone defects of rabbit radius and enhancing angiogenesis and new bone formation.Methods EPCs isolated from New Zealand white rabbit bone marrow were cultured,identified and seeded into nHAC/PLA scaffolds.And the growth of EPCs in scaffolds was observed under scanning electron microscopy ( SEM ).Thirty-six were randomly divided into 3 groups to establish segmental bone defect models in radii.Two groups were implanted with EPCs/scaffolds constructs ( group A,n =16) and scaffolds alone (group B,n =16) respectively.The remaining four rabbits were used as negative control (group C) and nothing was implanted.Animals were sacrificed at different timepoints and radii harvested to undergo radiological examination,histological examination and microvessle density test.Results These cells isolated from bone marrow were confirmed as EPCs.SEM showed that EPCs attached to the nHAC/PLA scaffolds, grew and proliferated well.Animal experiments revealed that radiological scores (5w:2.25 ±0.50 vs 1.00 ±0.00; 10w:2.75 ±0.50 vs 1.75 ±0.50; 15w:4.25 ±0.50 vs 3.0 ± 0.0 ; each P ＜ 0.05 ),percentage of new bone formation area in bone defect regions (5w:29.0％ ± 3.5％ vs 8.1％ ±0.8％; 10w:63.4％ ±5.5％ vs 16.6％ ±1.3％; 15w:96.0％ ±4.3％ vs 34.0％ ±6.6％ ; each P ＜ 0.05 ) and microvessel density ( 2w:13.5 ± 0.9 vs 4.3 ± 1.0; 5w:9.8 ± 0.7 vs 4.8 ±0.3 ; 10w:7.0 ± 0.4 vs 4.5 ± 0.4; each P ＜ 0.05 ) in group A were significantly higher than those in group B.No new bone formation occurred in group C.Conclusion The composite structure of EPCs-nHAC/PLA can enhance angiogenesis and new bone formation in segmental bone defects in rabbit radii.It may become a potential candidate of promoting revascularization of tissue engineering bone and repairing large bone defects. Key words: Reconstructive surgical procedures; Osteogenesis; Tissue therapy; Stem cells