Department of Health Sciences and Technology, Institute of Translational Medicine, Laboratory of Applied Mechanobiology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich, 8093, Switzerland.
Biomater Sci. 2017 Sep 26;5(10):2009-2023. doi: 10.1039/c7bm00276a.
Blood clots stop bleeding and provide cell-instructive microenvironments. Still, in vitro models used to study implant performance typically neglect any possible interactions of recruited cells with surface-adhering blood clots. Here we study the interaction and synergies of bone marrow derived human mesenchymal stem cells (hMSCs) with surface-induced blood clots in an in vitro model by fluorescence microscopy, scanning and correlative light and electron microscopy, ELISA assays and zymography. The clinically used alkali-treated rough titanium (Ti) surfaces investigated here are known to enhance blood clotting compared to native Ti and to improve the healing response, but the underlying mechanisms remain elusive. Here we show that the presence of blood clots synergistically increased hMSC proliferation, extracellular matrix (ECM) remodelling and the release of matrix fragments and angiogenic VEGF, but did not increase the osteogenic differentiation of hMSCs. While many biomaterials are nowadays engineered to release pro-angiogenic factors, we show here that clot-entrapped blood cells on conventional materials in synergy with hMSCs are potent producers of pro-angiogenic factors. Our data might thus not only explain why alkali-treatment is beneficial for Ti implant integration, but they suggest that the physiological importance of blood clots to create pro-angiogenic environments on implants has been greatly underestimated. The importance of blood clots might have been missed because the pro-angiogenic functions get activated only upon stimulation by synergistic interactions with the invading cells.
血液凝块可以止血，并提供细胞指导的微环境。然而，用于研究植入物性能的体外模型通常忽略了募集细胞与表面附着的血液凝块之间可能存在的任何相互作用。在这里，我们通过荧光显微镜、扫描和相关的光镜和电子显微镜、ELISA 检测和组织化学检测研究了骨髓来源的人间充质干细胞（hMSC）与体外模型中表面诱导的血液凝块的相互作用和协同作用。这里研究的临床使用的碱处理粗糙钛（Ti）表面已知与天然 Ti 相比能增强血液凝固并改善愈合反应，但潜在的机制仍不清楚。在这里，我们表明，血液凝块的存在协同增加了 hMSC 的增殖、细胞外基质（ECM）重塑以及基质片段和血管生成 VEGF 的释放，但不会增加 hMSC 的成骨分化。虽然现在许多生物材料被设计成释放促血管生成因子，但我们在这里表明，在传统材料上与 hMSC 协同作用的血栓捕获的血细胞是促血管生成因子的有力产生者。因此，我们的数据不仅可以解释为什么碱处理对 Ti 植入物的整合有益，而且还表明血液凝块在植入物上产生促血管生成环境的生理重要性被大大低估了。血液凝块的重要性可能被忽视了，因为促血管生成功能只有在与入侵细胞协同作用的刺激下才会被激活。
