Bone formation mediated by local administration of thymosin β4 in distraction osteogenesis / 中华创伤骨科杂志

ABSTRACT

Objective To explore the effect and mechanism of local administration of thymosin β4 (Tβ4) on bone regeneration in a distraction osteogenesis model of rat fenur.Methods Sixty Sprague-Dawley rats were randomly divided into groups A,B and C in this study.A distraction osteogenesis model was established in the left femur after osteotomy.At the end of distraction period,the bone regeneration area in group A was subjected to no treatment,that in group B to injection of phosphate buffer saline (PBS),and that in group C to injection of Tβ4.On days 22,29 and 43 postoperatively,the rats from each group were randomly sacrificed and processed for observation of bone regeneration in the distraction osteogenesis area using radiography,Micro-CT,histology and immunohistochemical staining.RT-PCR was used to detect the expression of related genes as well.Results Radiography revealed that the bone regeneration in group C was superior to that in groups A and B on days 22,29 and 43 postoperatively.Micro-CT examination showed significantly increased bone volume (BV),bone mineral density (BMD) and ratio of bone volume to tissue volume (BV/TV) in group C on days 22,29 and 43 postoperatively,and significantly decreased ratio of bone surface area to bone volume on postoperative day 43 in comparison with groups A and B(P ＜ 0.05).HE staining indicated that local capillary density was significantly higher in group C than in groups A and B after local administration of Tβ4 in the distraction osteogenesis.Immunohistochemical staining showed that the capillary density and osteoblasts in group C were higher than in groups A and B.RT-PCR results revealed significantly higher expression of eNOS and Osterix mRNA in the local callus in group C on postoperative day 22 than in groups A and group B (P ＜ 0.05).Conclusion Local administration of thymosin β4 may promote bone formation,which is probably related to the increased expression of eNOS and Osterix.