Huang Chenglong, Zhao Song, Cheng Biao, Chen Gang, Pan Jieen
Department of Orthopedics, Clinical Medical School, the Affiliated Shanghai No.10 People's Hospital, Nanjing Medical University, Shanghai, 200072, P.R.China.
Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, P.R.China.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2020 Sep 15;34(9):1177-1183. doi: 10.7507/1002-1892.202001029.
To assess the effect of microfracture and biomimetic hydrogel scaffold on tendon-to-bone healing in a rabbit rotator cuff tear model.
Gelatin and methacrylic anhydride were used to synthesize gelatin methacryloyl (GelMA). Then the GelMA were treated with ultraviolet rays and vacuum freeze-drying method to obtain a biomimetic hydrogel scaffold. The morphology of the scaffold was observed by gross observation and scanning electron microscope. Degradation of the scaffold was determined at different time points. Twenty-four adult New Zealand rabbits, weighting 2.8-3.5 kg and male or female, were surgically created the bilateral acute rotator cuff tear models. One shoulder was treated with microfractures on the footprint and transosseous suture (control group, =24). The other shoulder was treated with the same way, except for putting the scaffold on the footprint before transosseous suture (experimental group, =24). The general conditions of rabbits were observed postoperatively. Tendon-to-bone healing was evaluated by gross observation, Micro-CT, HE staining, and bio-mechanical testing at 4 and 8 weeks after operation.
The scaffold was white and has a porous structure with pore size of 31.7-89.9 μm, which degraded slowly in PBS solution. The degradation rate was about 95% at 18 days. All the rabbits survived to the completion of the experiment. Micro-CT showed that there was no obvious defect and re-tear at the tendon-to-bone interface in both groups. No difference was found in bone mineral density (BMD), tissue mineral density (TMD), and bone volume/total volume (BV/TV) between the two groups at 4 and 8 weeks postoperatively ( >0.05). HE staining showed that the fibrous scar tissue was the main component at the tendon-to-bone interface in the control group at 4 and 8 weeks postoperatively; the disorderly arranged mineralized cartilage and fibrocartilage formation were observed at the tendon-to-bone interface in the experimental group at 4 weeks, and the orderly arranged cartilage formation was observed at 8 weeks. Besides, the tendon maturation scores of the experimental group were significantly higher than those of the control group at 4 and 8 weeks ( <0.05). There was no significant difference in the ultimate load to failure and stiffness between the two groups at 4 weeks ( >0.05); the ultimate load to failure at 8 weeks was significantly higher in the experiment group than in the control group ( =4.162, =0.009), and no significant difference was found in stiffness between the two groups at 8 weeks ( =2.286, =0.071).
Compared with microfracture alone, microfracture combined with biomimetic hydrogel scaffold can enhance tendon-to-bone healing and improve the ultimate load to failure in rabbits.
在兔肩袖撕裂模型中评估微骨折和仿生水凝胶支架对肌腱-骨愈合的影响。
使用明胶和甲基丙烯酸酐合成甲基丙烯酰化明胶（GelMA）。然后通过紫外线和真空冷冻干燥法处理GelMA以获得仿生水凝胶支架。通过大体观察和扫描电子显微镜观察支架的形态。在不同时间点测定支架的降解情况。24只成年新西兰兔，体重2.8 - 3.5 kg，雌雄不限，通过手术建立双侧急性肩袖撕裂模型。一侧肩部在足迹处进行微骨折并经骨缝合（对照组，n = 24）。另一侧肩部采用相同方法处理，但在经骨缝合前将支架放置在足迹处（实验组，n = 24）。术后观察兔的一般情况。在术后4周和8周通过大体观察、Micro-CT、HE染色和生物力学测试评估肌腱-骨愈合情况。
支架呈白色，具有孔径为31.7 - 89.9μm的多孔结构，在PBS溶液中降解缓慢。18天时降解率约为95%。所有兔均存活至实验结束。Micro-CT显示两组肌腱-骨界面均无明显缺损和再撕裂。术后4周和8周两组间骨密度（BMD）、组织矿物质密度（TMD）和骨体积/总体积（BV/TV）无差异（P > 0.05）。HE染色显示术后4周和8周对照组肌腱-骨界面主要为纤维瘢痕组织；实验组术后4周肌腱-骨界面观察到矿化软骨排列紊乱和纤维软骨形成，8周时观察到软骨形成有序。此外，实验组在4周和8周时的肌腱成熟度评分显著高于对照组（P < 0.05）。4周时两组间的极限破坏载荷和刚度无显著差异（P > 0.05）；8周时实验组的极限破坏载荷显著高于对照组（t = 4.162，P = 0.009），8周时两组间刚度无显著差异（t = 2.286，P = 0.071）。
与单纯微骨折相比，微骨折联合仿生水凝胶支架可增强兔的肌腱-骨愈合并提高极限破坏载荷。
