Chastain Sara R, Kundu Anup K, Dhar Sanjay, Calvert Jay W, Putnam Andrew J
Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92697, and Long Beach Venterans Affairs Healthcare System 90822, USA.
J Biomed Mater Res A. 2006 Jul;78(1):73-85. doi: 10.1002/jbm.a.30686.
The osteogenic potential of mesenchymal stem cells (MSCs) cultured on poly(lactide-co-glycolide) (PLGA) or poly(caprolactone) (PCL), two widely used polymeric biomaterials that have been reported to differentially support osteogenic differentiation, was compared in these studies. Here we report that MSCs cultured in 3-D PLGA scaffolds for up to 5 weeks significantly upregulate osteocalcin gene expression levels. By contrast, osteocalcin expression was markedly downregulated in 3-D PCL-based constructs over the same time course. We hypothesized that differential adsorption of extracellular matrix (ECM) proteins present in serum-containing culture medium and subsequent differences in integrin-mediated adhesion are responsible for these differences, and tested this hypothesis using thin (2-D) polymeric films. Supporting this hypothesis, significant amounts of fibronectin and vitronectin deposited onto both materials in serum-containing osteogenic media, with type-I collagen present in lower amounts. Adhesion-blocking studies revealed that MSCs adhere to PCL primarily via vitronectin, while type-I collagen mediates their attachment to PLGA. These adhesive mechanisms correlated with higher levels of alkaline phosphatase (ALP) activity after 2 weeks of monolayer culture on PLGA versus PCL. These data suggest that the initial adhesion of MSCs to PLGA via type-I collagen fosters osteogenesis while adhesion to PCL via vitronectin does not, and stress the need for an improved molecular understanding of cell-ECM interactions in stem cell-based therapies.
在这些研究中，比较了在聚（丙交酯-共-乙交酯）（PLGA）或聚己内酯（PCL）上培养的间充质干细胞（MSC）的成骨潜力，这两种广泛使用的聚合物生物材料据报道对成骨分化有不同的支持作用。在此我们报告，在3-D PLGA支架中培养长达5周的MSC显著上调骨钙素基因表达水平。相比之下，在相同时间进程中，基于3-D PCL的构建体中骨钙素表达明显下调。我们假设，含血清培养基中存在的细胞外基质（ECM）蛋白的差异吸附以及整合素介导的黏附随后的差异是造成这些差异的原因，并使用薄（2-D）聚合物膜对这一假设进行了测试。支持这一假设的是，在含血清的成骨培养基中，大量纤连蛋白和玻连蛋白沉积在两种材料上，而I型胶原的含量较低。黏附阻断研究表明，MSC主要通过玻连蛋白黏附于PCL，而I型胶原介导它们与PLGA的附着。这些黏附机制与在PLGA上单层培养2周后比在PCL上更高水平的碱性磷酸酶（ALP）活性相关。这些数据表明，MSC通过I型胶原与PLGA的初始黏附促进成骨，而通过玻连蛋白与PCL的黏附则不然，并强调在基于干细胞的治疗中需要对细胞-ECM相互作用有更好的分子理解。
