聚乙烯醇/羟基磷灰石复合水凝胶移植修复兔膝关节软骨缺损

背景目前临床治疗由创伤、骨关节炎等引起的关节软骨病损的方法不能使受损的软骨在形态学、生化和生物力学方面恢复至正常,修复组织不能达到良好的远期疗效,常在短期内发生退行性变.目的探讨聚乙烯醇/羟基磷灰石复合水凝胶移植修复兔膝关节软骨缺损的疗效及了解其组织相容性.设计随机对照动物实验.单位中山大学附属第三医院动物实验中心.材料实验于2003-10/2004-04在中山大学附属第三医院动物实验中心完成.成年健康新西兰白兔20只,雄性12只,雌性8只,体质量2.1～3.0 kg,由中山大学动物实验中心提供.饲养环境温度20℃,相对湿度40%.将兔子随机分成空白对照组(n=6)和实验组(n=14).方法采用溶胶凝胶法原位复合制备聚乙烯醇/羟基磷灰石水凝胶,通过体外力学性能测试,采用日本岛津公司生产的AG-1型万能电子拉力试验机对材料的拉伸性能进行测试,拉伸速度为500 mm/min.空白对照组不作任何处理,实验组于软骨缺损处植入圆柱形聚乙烯醇/羟基磷灰石复合水凝胶,嵌压固定.术后动物单笼关养,所有术肢不予固定,任其自由活动,常规用青、链霉素抗感染治疗.术后第4,8,12周空气栓塞法每批处死6～7只兔子,取患膝关节作大体、光镜观察.主要观察指标主要结局两组家兔膝关节软骨缺损的大体和组织学改变.次要结局聚乙烯醇/羟基磷灰石复合水凝胶的体外拉伸强度与浸泡时间的关系.结果①两组家兔膝关节软骨缺损的大体和组织学改变术后4周,实验组的缺损由聚乙烯醇/羟基磷灰石充填,材料与软骨下骨连接无间隙,术后12周,植入材料与软骨交界面有大量的软骨细胞增殖,未见软骨退变,植入材料与软骨下骨连接紧密,有骨样组织长入;空白对照组缺损主要由纤维肉芽组织修复.②聚乙烯醇/羟基磷灰石复合水凝胶的体外拉伸强度与浸泡时间的关系聚乙烯醇/羟基磷灰石复合水凝胶的力学性能在浸泡初期出现上升,随后有所下降,此后比较平稳,但均比初始强度高.结论聚乙烯醇/羟基磷灰石复合水凝胶与软骨下骨结合良好,没有炎性细胞浸润,无免疫排斥反应发生,说明组织相容性良好,植入后周围软骨细胞无退行性改变,说明具有一定的力学作用,可以作为良好的人工关节软骨替代材料.本实验采用溶胶凝胶法原位复合制备聚乙烯醇/羟基磷灰石水凝胶,避免了涂层材料的降解与剥脱,并能较长时间保持良好的力学特性.

Experimental study of rabbit knee joint articular cartilage defects repaired with transplantation of polyvinyl alcohol/hydroxyapatite composite hydrogel

BACKGROUND: At present, the therapy to treat articular cartilage lesions caused by trauma, osteoarthritis and other diseases fails to repair the damaged cartilage to its normal state morphologically, biochemically and biomechanically and for the repaired tissues, good long-term effect doesn't happen and retrograde degeneration happens in a short period.OBJECTIVE: To study the curative effect of transplantation of polyvinyl alcohol/hydroxyapatite (PVA/HA) composite hydrogel to repair rabbit knee joint articular cartilage defects and to learn about its biocompatibility with host tissues.DESIGN: A randomized controlled experimental animal study.SETTING: The Animal experimental Center of the Third Affiliated Hospital of Sun Yat-sen University.MATERIALS: The experiment was conducted at the Animal Experimental Center of the Third Affiliated Hospital of Sun Yat-san University. Totally 20 adult healthy New Zealand white rabbits including 12 males and 8 females, with a body mass of 2.1 to 3.0 kg were provided by the Animal Experimental Center of Sun Yat-sen University. All animals were bred in an environment of 20℃ and 40% of humidity. The rats were randomized into the blank control group (n=6) and the experimental group (n=14).METHODS: Polyvinyl alcohol/hydroxyapatite composite hydrogel was made by sol-gel method of hydroxyapatite powder. The tensility was tested at a pulling speed of 500 mm/min by AG-1 omnipotence electronic pulling tester (produced by Shimadz Co. of Japan) through mechanical property test in vitro. Rabbits in the control group received no other procedures while the rabbits in the experimental group had their knee joint articular cartilage defects repaired with transplantation of cylindrical PVA/HA composite hydrogel, fixed by inlaying the hydrogel into the defect. Fed in the cage alone postoperatively, all animals were permitted to move without any immobilization to the operated limbs. Routine therapy of benzylpenicillin and streptomycin anti-infection was performed. Then, 6-7 animals were sacrificed by the intravenous injection of air emboli 4, 8 and 12 weeks after the operation for examining the specimens from the operated knees macroscopically and microscopically.MAIN OUTCOME MEASURES: Primary results: macroscopic and histological evaluation of the articular cartilage defects of each group. Secondary results: The relationship between the tensile strength of PVA/HA composite hydrogel in vitro and its soaking time.fects of the rabbits in the two groups: 4 weeks after the operation, the defects in the experimental group were filled up with PVA/HA. No space was found between the material and the subchondral bone. 12 weeks after the operation. A lot of chondrocytes proliferated on the boundaries between the grafts and the normal cartilage and no cartilage degeneration took place.The graft's bottom was tied to the subchondral bone and some osteoid tissues had grown into it. Fiber granulation tissue repair mainly showed up in HA composite hydrogel in vitro and its soaking time: Tensile strength of PVA/HA increased in the early soaking time (in 6 days), then decreased a bit, and then became stable henceforth. But the eventual tensile strength was higher than it was at the beginning.CONCLUSION: PVA/HA composite hydrogel was well combined with subchondral bone without inflammatory cell infiltration and immunological rejection, suggesting a good biocompatibility with host tissues. After the implantation, there was no cartilage cellular degeneration, suggesting that there was certain mechanical effect. This indicates that PVA/HA can be used as a good substitute material for artificial cartilage. Polyvinyl alcohol / hydroxyapatite composite hydrogel was adopted by sol-gel in situ method of hydroxyapatite powder to avoid the degradation and exfoliation of coat materials and to keep good mechanical characteristics for a long time.