骨形态发生蛋白-2基因治疗对假体-骨界面影响的实验研究

Effects of bone morphogenetic protein-2 gene therapy on the bone-implant interface: an experimental study with dogs

目的观察假体周围骨缺损重建中,骨形态发生蛋白(BMP)2基因治疗对假体骨界面骨整合的影响。方法14条成年Beagle犬,于双侧股骨外髁造成横向骨缺损,植入光滑面钛合金假体后保持假体周围3mm骨缺损。共28侧分成4组:空白对照组(2侧),缺损区未行处理;其余分3组为无细胞组(8侧)、细胞组(8侧)和基因组(10侧),采用压缩植骨技术重建股骨髁假体周围骨缺损,分别植入犬异体冻干骨、复合自体骨髓基质干细胞的冻干骨以及复合转BMP2基因自体骨髓基质干细胞的冻干骨。通过组织学、组织形态计量学及生物力学评估假体骨界面的愈合和整合。结果术后6周,基因组假体表面明显较多的新骨沉积,可见散在的假体与新骨间点状接触,假体骨接触率(BIC)达10%左右,而空白对照组、无细胞组和细胞组界面为厚薄不一的软组织,BIC为0;12周时,空白对照组界面仍是较厚的软组织,无细胞组和细胞组的界面主要为结缔组织纤维膜,少量点状骨接触,BIC均未超过10%,基因组的假体骨界面主要为骨组织,假体骨界面可见连续性骨接触,部分BIC达50%,远高于前两组(39.2±7.5比8.4±1.3、7.2±1.5,均P<0.01)。各组的界面推出强度随时间增加,基因组的强度在各个时间段均远高于前两组(1.40±0.22比0.09±0.04、0.08±0.04,均P<0.01)。结论BMP2基因治疗可明显提高假体骨界面的骨整合。

Objective To investigate the effects of bone morphogenetic protein-2 (BMP-2) gene therapy on the bone-implant interface in the reconstruction of periprosthetic bone defect. Methods Transverse defects were caused in the external condylae of both femurs of 14 adult Beagle dogs. Titanium alloy implants were inserted and a bone defect 3 mm wide around the titanium alloy implant was preserved. Then the total 28 defects were divided into 4 groups: 8 bone defects remained untreated (blank control group); 8 bone defects were implanted with heterogeneous freeze-dried bone by impaction grafting technique (non-cell group); 8 bone defects were implanted with heterogeneous freeze-dried bone loaded with autogenous bone marrow stromal cells (BMSCs) from the greater trochanter of the same dog (cell group); and 10 bone defects were implanted with freeze-dried allograft loaded with autogenous BMSCs from the greater trochanter of the same dog which were transfected by Adv-BMP-2 gene (gene group). Three, 6, and 12 weeks after implantation X-ray examination was carried out to observe the place of the implant and the absorption of the implants. Six and 12 weeks after the dogs were killed and their bone defects were taken out to undergo histological, histomorphometric and biomechanical examination to observe the healing and oseeointegration of the bone-implant interface. Results Histological examination showed that 6 weeks after implantation new bone formation was found on the implant surface and there was point contact between the bone and implant in the gene group with the bone-to-impact contact (BIC) of about 10%; and continuous soft tissue was found at bone-implant interface in all other groups. Twelve weeks after, there was thick soft tissue membrane between the new bone and implant in the blank control group; most of the interface was connective fibrous tissue in the non-cell group and cell group with point contact between the bone and implant and a BIC lower than 10%; and in the gene group the interface consisted mainly of bone tissue and continuous bone-implant contact was found with the BIC of 50%, significantly higher than those of the other 2 groups (both P<0.01). The mechanical strength of interface increased time-dependently in all groups, that of the gene group being significantly higher than those of the other 2 groups at any time-points (both P<0.01). Conclusion BMP-2 gene therapy can improve the osseointegration of bone-implant interface.