超长期缓释IGF-1的可注射复合微球材料对骨质疏松性骨缺损治疗机制的研究

Because osteoporosis needs long term treating, developing a prolong term controlled release carrier of drugs, protein or nucleic acid is one of the key issues in osteoporosis research field. Insulin-like Growth Factor 1 is one of the key factors in osteoporosis treatment research, but due to its limited acting cycle, which needs repeat injection,its application in the clinical fields was restricted. In our preliminary study, a new type of injectable nHAC/CS scaffold based on CS, nHA and Col was fabricated with a biomimetic strategy. Preliminary evidences showed that the nHAC/CS scaffold can repair the bone defect successfully. Based on early research, our ideas are as follows: (1) Preparing the polyester coating nHA/PLA microspheres carrying IGF-1/IGFBP3. By combining the polyester coating nHA/PLA microspheres with injectable nHAC/CS composite, developing the injectable composite microsphere materials,which can prolong term controlled release IGF-1. By optimizing the preparation of the coating structure and the microspheres, prolong term controlled releasing of IGF-1 for 18 months and maintaining its activity could be achieved; (2) Evaluating the physical and chemical properties, injectability and releasing function of the composite. Exploring the biocompatibility,toxicity and bone induction of the composite by cytology and histopathology methods; (3)Injecting the composite into the bone defect of the osteoporosis animal model,evaluating the bone defect repairing and bone metabolic regulating mechanism of IGF-1 by imaging, histochemistry, biomechanics methods. Providing new ideas in the development of the prolong term controlled release carrier,and new strategies for osteoporosis bone defect treatment.

由于骨质疏松治疗的长期性，研制一种可超长期缓释药物、蛋白或核酸的载体是该领域研究的关键问题，其中，IGF-1是其治疗研究的关键因子之一，但因作用周期有限、需反复注射给药等问题限制了临床应用。课题组前期研制了可注射nHAC/CS材料，初步证明材料骨修复性能良好，本课题拟在前期基础上:①制备载IGF-1/IGFBP3的聚酯涂层nHA/PLA微球，与可注射nHAC/CS材料复合，研制超长期缓释IGF-1的可注射复合微球材料，通过对微球及涂层结构的构建及优化，实现材料缓释IGF-1周期达18个月并保持活性的目标；②评价材料的理化性质、可注射及缓释性能，通过细胞学及组织病理学等方法评估材料的生物相容性、毒性及骨诱导性能；③将材料注射入骨质疏松骨缺损动物模型内，通过影像学、组织化学、生物力学等探讨材料对骨修复和骨代谢的双重调控机制，为超长期缓释载体的研制提供新思路，为骨质疏松骨缺损的治疗提供新策略。

针对骨质疏松治疗的长期性，本项目研制了一种可超长期缓释IGF-1的双层微球载体系统。课题组首先采用nHA和PLA制备出载rhIGF-1的nHA/PLA/Eu双层微球，优化微球性能，调整微球载药量及载药率，最终制备出超长期缓释IGF-1或阿仑膦酸钠（Ale）的双层复合微球材料；微球表面较光滑，大小均一，颗粒分散良好；体外药物释放结果显示rhIGF-1的缓释周期超过180天，复合材料可实现IGF-1的平稳释放，释放性能优于IGF-1/PLA单层微球。体外细胞实验证实IGF-1/PLA/Eu双层微球具有良好的细胞相容性。动物实验采用采用两种年龄的雄性C57BL/6小鼠，分别为成年小鼠（3月龄）和老龄小鼠（10月龄）。将载rhIGF-1的nHA/PLA/Eu双层微球分别植入到雄性C57BL/6小鼠背部皮下。在6个月实验周期内，采用ELISA法检测小鼠血清、肝、骨的rhIGF-1含量；结果显示，体内药物释放周期特点与体外结果相一致。动物实验结果提示，微球能够对成年小鼠骨量和老龄小鼠软骨带来有益作用。对于成年小鼠，微球组的骨量显著高于对照组。对于老龄小鼠，微球组的OARSI评分显著低于对照组，说明微球治疗能够延缓老龄小鼠的关节退变。这些结果提示，nHA/PLA/Eu双层微球能够超长期缓释rhIGF-1，使得局部应用药物缓释系统来预防全身骨量丢失和软骨退变成为可能。该研究有助于深入了解IGF-1在骨矿化和关节软骨方面的生物学作用。通过超长期缓释IGF-1来延缓骨质疏松和软骨退变是一种很有潜力的治疗手段，为超长期缓释载体的研制提供新思路，为骨质疏松骨缺损的治疗提供新策略。