利用新型脂肪组织来源成骨诱导移植物在体预构血管化骨组织

大体积骨缺损修复是一个临床难题，应用脂肪来源干细胞（ASC）构建骨组织用于骨缺损修复已成为研究热点。但ASC的成骨分化能力会随传代次数增加而降低，且体外构建的骨移植物难以再血管化而限制了其临床转化。项目组预实验发现微粒脂肪组织可经体外增殖、软骨内成骨诱导培养直接分化成肥大软骨组织，但其机制尚不明确。我们认为细胞外基质（ECM）与整合素α5信号通路参与了维持ASC的分化潜能;且利用更加富含ASC和ECM的乳糜化脂肪组织，经过体外软骨内成骨诱导和体内组织预构技术，可能在体预构出血管化骨移植物。为此，我们拟采用机械法获取乳糜化脂肪组织，经过体外软骨内成骨诱导培育成肥大软骨组织，分析ECM与整合素α5在ASC增殖与软骨分化中所起的作用；然后利用裸大鼠腹壁浅血管束作为体内生物反应器，植入利用脂肪组织构建的肥大软骨组织，以期在体预构出大体积、血管化、功能化的骨移植物，为大体积骨缺损的修复提供新的思路。

Reconstructions of critical-sized bone defects is a clinical challenge. Adipose derived stem cells (ASCs)-based bone tissue engineering is a promising strategy for bone defect reconstruction. However, it is well-known that the osteogenic differentiation potential of ASCs decreases with cell passaging. Furthermore, revascularization of in vitro tissue-engineered bone grafts remains a challenge. Our pilot experimental have found that nanofat can directly differentiate into hypertrophic cartilage tissue after a period of in vitro proliferation and endochondral ossification induction. However, its mechanism remains unclear. We hypothesized that extracellular matrix (ECM) and α5 integrin signaling maintain the differentiation potential of ASCs. Therefore, osteogenic and vascularized bone grafts can be generated directly by human fat tissue and tissue prefabrication technique. To prove it, we going to harvest emulsified fat tissue, which rich in ASCs and SEM, by mechanical treatment and centrifugation. The emulsified fat tissue will be mixed with porous hydroxyapatite granules and submitted for in vitro proliferation and endochondral ossification to generate hypertrophic cartilage tissue. The effect of ECM and α5-integrin on proliferation and differentiation of ASCs will be analyzed. Then, an in vivo bioreactor model will be constructed by superficial inferior epigastric vessel bundle in nude rat and used to in vivo cultivate the fat tissue-derived hypertrophic cartilage tissue. Finally, the vascularized, functional bone grafts will be prefabricated after 12 weeks of in vivo cultivation. After this study, we hope the results can provide a new insight and solution of clinical reconstruction of critical-sized bone defects.