Wacker Bradley K, Alford Shannon K, Scott Evan A, Das Thakur Meghna, Longmore Gregory D, Elbert Donald L
Department of Biomedical Engineering and Center for Materials Innovation, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
Biophys J. 2008 Jan 1;94(1):273-85. doi: 10.1529/biophysj.107.109074. Epub 2007 Sep 7.
Sphingosine 1-phosphate (S1P) is a potent chemokinetic agent for endothelial cells that is released by activated platelets. We previously developed Arg-Gly-Asp (RGD)-containing polyethylene glycol biomaterials for the controlled delivery of S1P to promote endothelialization. Here, we studied the effects of cell adhesion strength on S1P-stimulated endothelial cell migration in the presence of arterial levels of fluid shear stress, since an upward shift in optimal cell adhesion strengths may be beneficial for promoting long-term cell adhesion to materials. Two RGD peptides with different integrin-binding specificities were added to the polyethylene glycol hydrogels. A linear RGD bound primarily to beta(3) integrins, whereas a cyclic RGD bound through both beta(1) and beta(3) integrins. We observed increased focal adhesion formation and better long-term adhesion in flow with endothelial cells on linear RGD peptide, versus cyclic RGD, even though initial adhesion strengths were higher for cells on cyclic RGD. Addition of 100 nM S1P increased cell speed and random motility coefficients on both RGD peptides, with the largest increases found on cyclic RGD. For both peptides, much of the increase in cell migration speed was found for smaller cells (<1522 microm(2) projected area), although the large increases on cyclic RGD were also due to medium-sized cells (2288-3519 microm(2)). Overall, a compromise between high cell migration rates and long-term adhesion will be important in the design of materials that endothelialize after implantation.
1-磷酸鞘氨醇（S1P）是一种由活化血小板释放的、对内皮细胞具有强大趋化作用的物质。我们之前开发了含精氨酸-甘氨酸-天冬氨酸（RGD）的聚乙二醇生物材料，用于S1P的可控释放以促进内皮化。在此，我们研究了在动脉水平的流体剪切应力存在下，细胞黏附强度对S1P刺激的内皮细胞迁移的影响，因为最佳细胞黏附强度的上调可能有利于促进细胞对材料的长期黏附。将两种具有不同整合素结合特异性的RGD肽添加到聚乙二醇水凝胶中。线性RGD主要与β(3)整合素结合，而环状RGD则通过β(1)和β(3)整合素结合。我们观察到，与环状RGD相比，线性RGD肽上的内皮细胞在流动状态下形成的黏着斑增加，长期黏附更好，尽管环状RGD上细胞的初始黏附强度更高。添加100 nM S1P可提高两种RGD肽上细胞的速度和随机运动系数，其中环状RGD上的增加幅度最大。对于两种肽，细胞迁移速度的增加主要见于较小的细胞（投影面积<1522 平方微米），尽管环状RGD上的大幅增加也归因于中等大小的细胞（2288 - 3519平方微米）。总体而言，在设计植入后能实现内皮化的材料时，在高细胞迁移率和长期黏附之间达成平衡将很重要。
