Wiester Lisa M, Giachelli Cecilia M
Department of Bioengineering, University of Washington, Seattle, WA 98195-7335, USA.
J Heart Valve Dis. 2003 Sep;12(5):605-16.
Aortic valve interstitial cells (VIC), the most prevalent valve leaflet cells, have not been well studied. However, recent interest in constructing tissue-engineered living heart valves has provided motivation to further an understanding of the molecular and cellular biology of VIC. Since cell-extracellular matrix interactions are critical for tissue morphogenesis, adhesive interactions and integrin function in VIC were investigated.
Bovine and baboon VIC were isolated and characterized by morphology, cytoskeletal protein expression and integrin expression. The interaction of VIC integrin alpha9beta1 with osteopontin, a ligand known to be up-regulated in the wounded valve, was examined. The ability of bovine VIC alpha9beta1 to mediate adhesion, focal contact formation, migration and proliferation when plated on the immobilized osteopontin substrates, was investigated.
Cultured bovine VIC possessed characteristics of both fibroblasts and smooth muscle cells. Like fibroblasts, bovine VIC had an elongated morphology with long cytoplasmic processes. Like smooth muscle cells, bovine VIC expressed alpha-smooth muscle actin and SM22alpha. Using fluorescent flow cytometry, the surface expression of integrins alpha9beta1 and alpha(v)beta3 in bovine VIC and integrins alpha1beta1, alpha2beta1, and alpha5beta1 in baboon VIC was identified. Expression of alpha9beta1 in cultured VIC and in native valve leaflets was further confirmed by Western blot and RT-PCR analysis. Bovine VIC were found to adhere to the 30N fragment of osteopontin in an alpha9beta1-dependent manner, and this interaction was mediated through the SVVYGLR motif. Bovine VIC also formed focal contacts through the alpha9beta1 integrin, but osteopontin (30N) did not stimulate migration or proliferation of bovine VIC through the integrin alpha9beta1.
Integrin alpha9beta1 appears to be predominantly involved in controlling anchorage rather than movement or proliferation, in bovine VIC. For tissue engineering, knowledge of the VIC integrin profile can be applied to the rational design of scaffolds with the appropriate ligands for tissue formation. The VIC a9beta1-SVVYGLR interaction could be exploited to promote cell anchorage within a tissue engineering scaffold.
主动脉瓣间质细胞（VIC）是最常见的瓣叶细胞，但尚未得到充分研究。然而，近期对构建组织工程化活心脏瓣膜的兴趣促使人们进一步了解VIC的分子和细胞生物学。由于细胞与细胞外基质的相互作用对组织形态发生至关重要，因此研究了VIC中的黏附相互作用和整合素功能。
分离牛和狒狒的VIC，并通过形态学、细胞骨架蛋白表达和整合素表达进行表征。检测VIC整合素α9β1与骨桥蛋白（一种已知在损伤瓣膜中上调的配体）的相互作用。研究了牛VICα9β1在固定化骨桥蛋白底物上介导黏附、焦点接触形成、迁移和增殖的能力。
培养的牛VIC具有成纤维细胞和平滑肌细胞的特征。与成纤维细胞一样，牛VIC形态细长，有长的细胞质突起。与平滑肌细胞一样，牛VIC表达α-平滑肌肌动蛋白和SM22α。使用荧光流式细胞术，鉴定了牛VIC中整合素α9β1和α(v)β3以及狒狒VIC中整合素α1β1、α2β1和α5β1的表面表达。通过蛋白质印迹和RT-PCR分析进一步证实了培养的VIC和天然瓣叶中α9β1的表达。发现牛VIC以α9β1依赖性方式黏附于骨桥蛋白的30N片段，这种相互作用通过SVVYGLR基序介导。牛VIC还通过α9β1整合素形成焦点接触，但骨桥蛋白（30N）不会通过整合素α9β1刺激牛VIC的迁移或增殖。
在牛VIC中，整合素α9β1似乎主要参与控制锚定，而不是运动或增殖。对于组织工程，VIC整合素谱的知识可应用于合理设计具有适当配体的支架以促进组织形成。VIC的α9β1-SVVYGLR相互作用可用于促进细胞在组织工程支架内的锚定。
