早期细胞募集促进PLGA/TCP多孔支架材料成骨作用的研究

It was proved that different porous scaffold can promote the bone repair, but most of the studies focused on the effect of implant biomaterials on promoting the bone defect repair long time after implantation.The common mechanism well been known are osteoconduction of the biomaterials itself and osteoinductivity of growth factors which incorporated into the biomaterials. In our previous work, we found the porous PLGA/TCP scaffold could partly promote the bone regeneration without incorporation of growth fractors or stem cells. Though studies showed that the different biomaterials could promote the bone repair whether combined with or without growth factors or stem cells and it is well know that the host progenitor cells play an important role during bone healing. The critical open question is how the host cells take part into the tissue repair and no direct evidence showed the early host cells activity inside of the materials in vivo. That is to say, the early interaction between the biomaterials and host cells is still unknow. We suggestted that the host cells might take part in the bone repair not only during osteoconduction but also during osteoinduction.Based on the previous work, the investigators formulated the hypothesis that the porous scaffold materials can promote the homing and enriching of host cells in bone marrow cavity at early stage after implantation and these cells can spontaneously differentiate into osteoblast to promote the bone formation under micro-environment in vivo without ectogenous growth factors or cells.To test our hypothesis: (1) In vitro study: Observation of the attachment, proliferation, migration and osteogenesis of rabbit BMSCs on the porous PLGA/TCP scaffold. (2) In vivo study: A:To observe the early interaction between porous scaffold and host cells in vivo, we will implant the porous scaffold into the bone marrow cavity of rabbit and take it out to seperate the cells attached to the porous scaffold for quality and quantity. B: The growth factors or cells will be added into the bone marrow cavity after implantation of scaffold to identify the influence of ectogenous growth factors or stem cells on the early interaction between host cells and scaffold. C:The potential relationship between early host cells activity inside the porous scaffold and the later bone formation will also be explored.The object of study is not to develop novel biomaterials but to explore the early cellular mechanism of porous scaffold biomaterials on promoting bone repair using the common biomaterials and identify the relationship between early cellular mechanism and later bone repair. The well understanding of the early cellular mechanism may guide researchers to improve the bological properties of the biomaterials.Thus, the novel biomaterials can be developed for promote more cells homing and enriching to enhance the bone healing without additional growth factors or progenitor cells.

多孔支架生物材料如聚乳酸-羟基乙酸共聚物/磷酸三钙（PLGA/TCP）具有良好的生物相容性和降解性，能促进骨缺损修复，绝大多数研究仅观察生物材料植入体内晚期再生效果，通过晚期骨形成认识生物材料的骨传导和骨诱导作用，但并不清楚材料植入体内与机体之间早期的相互作用。将多孔 PLGA/TCP支架材料植入动物髓腔内，观察植入体内早期（2 周内）多孔材料与机体细胞之间的相互作用（材料对细胞的募集和富集作用），添加生长因子和/或细胞对早期材料-细胞相互作用的影响，观察支架材料在骨髓腔内的新骨形成。本研究揭示生物材料促进骨修复的早期细胞机制，即细胞在材料表面贴壁的时间、数量、类型及成骨分化时间等生物学行为，明确材料内早期胞活动与后期成骨的关系。有助于材料和医学研究者明确材料制备目的、改进材料生物学性能，开发更新颖生物材料以促进早期干细胞聚集及骨缺损修复。

多孔支架生物材料如聚乳酸-羟基乙酸共聚物/磷酸三钙（PLGA/TCP）具有良好的生物相容性和降解性，能促进骨缺损修复，绝大多数研究仅观察生物材料植入体内晚期再生效果，通过晚期骨形成认识生物材料的骨传导和骨诱导作用，但并不清楚材料植入体内与机体之间早期的相互作用。我们的研究将多孔 PLGA/TCP支架材料植入动物髓腔内，观察植入体内早期（2 周内）多孔材料与机体细胞之间的相互作用（材料对细胞的募集和富集作用），添加生长因子和/或细胞对早期材料-细胞相互作用的影响，观察支架材料在骨髓腔内的新骨形成。我们发现：.（1）多孔 PLGA/TCP支架材料(孔径500ul)体外适合骨髓基质干细胞的粘附、生长、分化，适合成骨细胞或者成骨前体细胞的粘附和生长。.（2）多孔支架材料适合新生血管长入。.（3）多孔支架材料在骨髓腔内具有对骨髓基质干细胞的早期募集、和富集作用。.（4）空白的多孔材料植入骨髓腔后，向骨髓腔内添加额外的骨髓基质干细胞可以增加材料对干细胞的富集作用，有利于材料后期成骨。.（5）体外复合骨髓基质干细胞的多孔材料植入骨髓腔内后，大多数细胞都能够保留在材料内部，且成骨能力优于空白多孔材料植入。.（6）空白的多孔材料植入骨髓腔后，添加BMP-2并不能增加材料上骨髓基质干细胞的数量，但是可以增加干细胞的成骨能力，有利于材料后期成骨。. 本研究的意义在于：揭示了生物材料在体内促进后期成骨的是由早期进入材料内的干细胞数量决定的，材料内的干细胞数量越多，成骨能力越强。生长因子促进生物材料成骨，也是通过促进材料内部的干细胞成骨作用来实现的。也就是说，无论是生物材料的骨传导性还是骨诱导性都是通过进入材料内部的干细胞数量来决定的。材料在体内是否具有早期干细胞募集和富集作用，可以预测材料在体内后期成骨作用的效果。掌握了研究体内材料-细胞相互作用的实验方法，这种早期观察材料-细胞之间响应的方法为研究新生物材料在体内成骨实验中节约时间成本。