胶原/壳聚糖复合支架植入大鼠不同部位降解速率的变化

Degradation rate of collagen-chitosan composite scaffold implanted into different rat tissues

背景:生物支架应随着新生组织的形成而逐渐降解,支架降解率是评价材料的一项重要指标。传统测试方法因存在一定限制而会影响对材料在不同部位降解率的评估。目的:评估胶原壳聚糖复合支架植入SD大鼠皮下、脊髓和脑组织的降解率,并初步探讨其机制。方法:制备3 mm×3 mm圆盘状胶原壳聚糖复合支架,通过扫描电子显微镜观测支架微观结构,对其主要的物理学特性进行测试;CCK-8法检测神经干细胞与支架共培养时的活力以评估支架生物相容性。将SD大鼠随机分为大脑组、脊髓组及皮下组,分别于脑皮质、脊髓T9处、背部T9皮下处植入胶原壳聚糖复合支架。于不同时间点灌注取材,每组3只大鼠取出支架称质量,评估支架体内降解率;组内其他大鼠用于制备组织切片,观察移植区支架与周围组织的组织学变化。结果与结论:1扫描电镜发现,胶原壳聚糖复合支架具有立体多孔结构,孔径大小能达到体内移植的生物学要求;2体内实验结果表明,植入胶原壳聚糖复合支架后未发生排斥反应,证明复合材料具有良好的生物相容性。皮下组降解速率最快,12 d即可降解完全,明显高于脊髓组和大脑组(P<0.05);脊髓组降解速率于第3周开始明显高于大脑组(P<0.05),脊髓组于12周基本降解完全,但大脑组仍有部分残余;3皮下组的支架周围血管数量和巨噬细胞浸润定性评分大于同一时间点的其他2组(P<0.05),且脊髓组高于大脑组(P<0.05);4结果说明,胶原/壳聚糖支架具有良好的生物相容性,在3个组织内的降解速率存在明显差异。组织工程学领域中平衡生物支架的降解率与人体重建速度时,应考虑靶向组织复杂的微环境和支架移植后的宿主反应的具体机制。

BACKGROUND： Biological scaffolds should be gradually degraded with the formation of new tissues, so the degradation rate is an important index for evaluating scaffold materials. Conventional testing methods make an impact on the assessment of the scaffold degradation rate at different sites due to some limitations. OBJECTIVE： To evaluate the degradation rate of collagen-chitosan（CG-CS） composite implanted into the subcutaneous, spinal cord and brain tissues of Sprague-Dawley rats and to explore the underlying mechanism. METHODS： A 3 mm×3 mm disc-shaped CG-CS composite scaffold was prepared, and its microstructure was observed under scanning electron microscope. Nerve stem cells were co-cultured with CG-CS scaffold, and then the cell viability was detected through cell counting kit-8 assay to assess the biocompatibility. Sprague-Dawley rats were randomly divided into three groups： cortex, spinal cord, and subcutaneous groups. The CG-CS scaffold was implanted into cortex, spinal cord T9, or back T9, respectively. The rats were sacrificed at different time points, and three rats in each group were subjected to the scaffold removal to evaluate the scaffold degradation rate. The resting rats were used to prepare the tissue sections for histological observation of the scaffold and the surrounding tissues.RESULTS AND CONCLUSION： Scanning electron microscope revealed that the CG-CS composite scaffold had a three-dimensional porous structure with a pore size that met the biological requirements of in vivo transplantation. The in vivo experiments showed that no graft rejection occurred, suggesting that the scaffold has good biocompatibility. The degradation rate was fastest in the subcutaneous group, and the scaffold was degraded completely with 12 days, which was significantly higher than that in the spinal cord and brain groups（P〈0.05）. The degradation rate in the spinal cord group was significantly higher than that in the brain group since the 3rd week（P〈0.05）; the scaffold degraded completely in the spinal cord group, while the partial scaffold could still be found in the brain group. The number of blood vessels and the scores of macrophage infiltration were as follows： subcutaneous group spinal cord group brain group（P〈0.05）. Our findings suggest that the CG-CS scaffold holds a good biocompatibility and its degradation rate differs significantly among groups. In the field of tissue engineering, the complex microenvironment of target tissues and the host response after stent implantation should have effects on the balance between the biodegradation rate and reconstitution rate of the organism.