Yip Cindy Ying Yin, Chen Jan-Hung, Zhao Ruogang, Simmons Craig A
Institute of Biomaterials and Biomedical Engineering, University of Toronto, ON, Canada.
Arterioscler Thromb Vasc Biol. 2009 Jun;29(6):936-42. doi: 10.1161/ATVBAHA.108.182394. Epub 2009 Mar 19.
Extensive remodeling of the valve ECM in calcific aortic valve sclerosis alters its mechanical properties, but little is known about the impact of matrix mechanics on the cells within the valve interstitium. In this study, the influence of matrix stiffness in modulating calcification by valve interstitial cells (VICs), and their differentiation to pathological phenotypes was assessed.
Primary porcine aortic VICs were cultured in standard media or calcifying media on constrained type I fibrillar collagen gels. Matrix stiffness was altered by changing only the thickness of the gels. Calcification did not occur in standard media, regardless of matrix stiffness. However, when VICs were grown in calcifying media on relatively compliant matrices with stiffness similar to that of normal tissue, they readily formed calcified aggregates of viable cells that expressed osteoblast-related transcripts and proteins. In contrast, VICs cultured in calcifying media on stiffer matrices (similar to stenotic tissue) differentiated to myofibroblasts and formed calcified aggregates that contained apoptotic cells. Actin depolymerization reduced aggregation on stiff, but not compliant, matrices. TGF-beta1 potentiated aggregate formation on stiff matrices by enhancing alpha-smooth muscle actin expression and cellular contractility, but not on compliant matrices attributable to downregulation of TGF-beta receptor I. Cell contraction by VICs inhibited Akt activation and enhanced apoptosis-dependent calcification on stiff matrices.
Differentiation of VICs to pathological phenotypes in response to biochemical cues is modulated by matrix stiffness. Although osteogenic or myofibrogenic differentiation of VICs can result in calcification, the processes are distinct.
钙化性主动脉瓣硬化中瓣膜细胞外基质（ECM）的广泛重塑改变了其力学性能，但关于基质力学对瓣膜间质内细胞的影响知之甚少。在本研究中，评估了基质硬度对瓣膜间质细胞（VICs）调节钙化及其向病理表型分化的影响。
将原代猪主动脉VICs在标准培养基或钙化培养基中培养于受限的I型纤维状胶原凝胶上。仅通过改变凝胶厚度来改变基质硬度。无论基质硬度如何，在标准培养基中均未发生钙化。然而，当VICs在钙化培养基中生长于与正常组织硬度相似的相对顺应性基质上时，它们很容易形成表达成骨细胞相关转录本和蛋白质的活细胞钙化聚集体。相反，在钙化培养基中于较硬基质（类似于狭窄组织）上培养的VICs分化为肌成纤维细胞，并形成含有凋亡细胞的钙化聚集体。肌动蛋白解聚减少了在硬基质而非顺应性基质上的聚集。转化生长因子-β1（TGF-β1）通过增强α-平滑肌肌动蛋白表达和细胞收缩性，增强了在硬基质上的聚集体形成，但在顺应性基质上未增强，这归因于TGF-β受体I的下调。VICs的细胞收缩抑制了Akt激活，并增强了在硬基质上依赖凋亡的钙化。
VICs对生化信号的病理表型分化受基质硬度调节。虽然VICs的成骨或肌纤维生成分化可导致钙化，但过程是不同的。
