Chen Xuening, Wang Jing, Chen Ying, Cai Hanxu, Yang Xiao, Zhu Xiangdong, Fan Yujiang, Zhang Xingdong
National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China.
J Mater Chem B. 2016 Apr 7;4(13):2280-2289. doi: 10.1039/c6tb00349d. Epub 2016 Mar 10.
Osteoinduction of calcium phosphate (CaP) ceramics has been widely confirmed and accepted, but the underlying mechanism has not been fully elucidated. This study investigates the early biomolecular events that contributed to the transduction of extracellular material cues outside in, when MSCs were cultured in osteoinductive biphasic calcium phosphate (BCP) ceramics, and explores their roles in BCP-induced osteogenesis. The results demonstrated that BCP ceramics had a strong adsorption affinity for serum proteins, which might favor cell adhesion and mediate the expression of the cell surface receptor - integrin. qRT-PCR analysis found that BCP ceramics significantly up-regulated integrin α and α genes under both in vitro and in vivo conditions. As integrins clustered together into focal contacts (cell adhesion sites), immunofluorescence staining showed that compared to glass surfaces, cells seeded in BCP ceramics formed a relatively short focal contact and exhibited a smaller cell size. Moreover, western blotting analysis indicated that BCP ceramics could activate down-stream MAPK signaling pathways, whereas blockage of either ERK or P38 signals could dramatically attenuate BCP-induced osteogenesis. These findings suggested that BCP ceramics might mediate cell adhesion through trans-membrane proteins - integrins - to realize the transduction of "outside-in signaling", and subsequently trigger the intracellular MAPK signaling cascade to induce the osteogenic differentiation of MSCs. They offered a promising principle for designing and fabricating tissue-inducing biomaterials to provide appropriate cues for target cells.
磷酸钙（CaP）陶瓷的骨诱导作用已得到广泛证实和认可，但其潜在机制尚未完全阐明。本研究调查了间充质干细胞（MSCs）在骨诱导双相磷酸钙（BCP）陶瓷中培养时，促成细胞外物质信号由外向内转导的早期生物分子事件，并探讨了它们在BCP诱导的成骨过程中的作用。结果表明，BCP陶瓷对血清蛋白具有很强的吸附亲和力，这可能有利于细胞黏附并介导细胞表面受体——整合素的表达。qRT-PCR分析发现，在体外和体内条件下，BCP陶瓷均能显著上调整合素α和α基因的表达。由于整合素聚集形成黏着斑（细胞黏附位点），免疫荧光染色显示，与玻璃表面相比，接种在BCP陶瓷中的细胞形成的黏着斑相对较短，且细胞尺寸较小。此外，蛋白质印迹分析表明，BCP陶瓷可激活下游的丝裂原活化蛋白激酶（MAPK）信号通路，而阻断ERK或P38信号均可显著减弱BCP诱导的成骨作用。这些发现表明，BCP陶瓷可能通过跨膜蛋白——整合素介导细胞黏附，以实现“由外向内信号”的转导，随后触发细胞内MAPK信号级联反应，诱导MSCs的成骨分化。它们为设计和制造组织诱导生物材料以向靶细胞提供适当信号提供了一个有前景的原理。
