BACKGROUND: Silk fibroin, the main component of silk fibroin biofilm, is a natural protein, but it is still a heterologous protein to the body. Its immunogenicity/toxicity is an important factor in determining the development prospects. OBJECTIVE: To evaluate the toxicity of absorbable silk fibroin biofilm and its degradation products on the rat immune system by muscle implantation experiments in rats. METHODS: Ten Wistar rats from Beijing Weitong Lihua Experimental Animal Technology Co., Ltd. were implanted with a long strip of 1 mm× 10 mm in the right gluteal muscle to observe the implant absorption and determine the implantation cycle. Seventy-two Wistar rats were assigned into control and experimental groups (n=36/group, 18 in either sexes) . A long strip of 1 mm×10 mm was implanted into the rat right gluteal muscle in the experimental group, and the control group received no implantation. Some of the rats were taken for histological examination and calculate the organ/weight ratio, at 26 weeks postoperatively. The spleen lymphocyte proliferation ability, NK cell activity, cell classification of T lymphocytes, and levels of interleukin 2 and tumor necrosis factor α were detected. Another part of the animals was taken for macrophage phagocytosis of erythrocytes cell capacity and antibody producing cell count. RESULTS AND CONCLUSION: (1) Silk fibroin biofilm was completely absorbed after implanted into the rat muscle for 26 weeks. (2) In female or male Wistar rats, the immune organs in the experimental group showed no significant changes in the appearance, weight and histological examination. There were no significant differences in the hematological indexes (hemoglobin, red blood cell count, hematocrit, blood platelet count and white blood cell count and classification) , spleen lymphocyte proliferation, NK cell activity, the ratio of T lymphocytes and their subpopulations, and the levels of interleukin 2 and tumor necrosis factor α had no significant differences between two groups (P> 0.05) . (3) In female or male Wistar rats, the macrophage phagocytosis of chicken erythrocytes cell capacity and antibody producing cell count showed no significant differences between two groups (P> 0.05) . (4) These results indicate that silk fibroin biofilm causes no immunosuppression or immunostimulation on immune organs, immune cells and immune molecules (cytokines) of rats.%背景:丝素生物膜的主要成分丝素蛋白是天然蛋白质, 但对机体来说仍属异源蛋白, 其免疫原性/毒性的强弱是决定其开发前景的重要因素.目的:通过大鼠肌肉植入实验评价可吸收丝素生物膜及其降解产物对大鼠免疫系统的毒性作用.方法:取10只Wistar大鼠 (北京维通利华实验动物技术有限公司提供) , 右侧臀肌植入1 mm×10 mm的长条状丝素生物膜, 观察植入物吸收情况, 确定实验植入周期.将72只Wistar大鼠分为对照组与受试物组, 每组36只, 每组内雌雄各18只, 受试物组在右侧臀肌植入1mm×10mm的长条状丝素生物膜, 对照组不放置植入物, 其余操作同受试物组, 植入26周后, 取其中一部分动物, 进行免疫器官脏体比及组织病理学检查, 以及脾淋巴细胞增殖能力、NK细胞活性、外周血T淋巴细胞及其亚群、细胞因子白细胞介素2和肿瘤坏死因子α检测;取另一部分动物, 进行巨噬细胞红细胞吞噬率与吞噬指数、溶血空斑数检测.结果与结论:①丝素生物膜植入大鼠肌肉26周基本全部吸收;②在雌性或雄性Wistar大鼠中, 受试物组免疫器官外观、质量和组织病理学检查未见有生物学意义的明显改变, 血液学指标 (血红蛋白、红细胞计数、红细胞压积、血小板计数、白细胞计数及分类) 、脾淋巴细胞增殖能力、NK细胞活性、外周血T淋巴细胞及其亚群、白细胞介素2和肿瘤坏死因子α水平与对照组比较差异均无显著性意义 (P>0.05) ; ③在雌性或雄性Wistar大鼠中, 受试物组巨噬细胞红细胞吞噬率与吞噬指数、溶血空斑数与对照组比较差异均无显著性意义 (P> 0.05) ;④结果表明, 丝素生物膜未引起大鼠机体的免疫抑制或免疫刺激等免疫毒性反应, 对机体免疫器官、免疫细胞和免疫分子 (细胞因子) 无明显影响.
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