Gene regulation by 3-D structure of extracellular matrix : a model for hepatic stellate cells

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Interaction between cells and extracellular matrix (ECM) is essential for cell functions such as morphology, proliferation, motility, differentiation, and gene expression. The native form of type I collagen fibrils is known to affect these cell functions and ECM degrading enzymes such as matrix metalloprotease-2 (MMP-2, gelatinase A) and MMP-13 (collageanase-3) in several cell types. In this study we examined the roles of ECM components including type I collagen in the regulation of morphology and function of cultured hepatic stellate cells (HSCs). HSCs showed myofibroblast-like cell shapes with well-developed stress fibers when cultured on type I collagen coated surface, whereas rounded shapes when cultured on Matrigel, suggesting that HSCs recognize native structure of extracellular type I collagen fibrils and change their morphology and function. Then we examined the involvement of intracellular signaling including protein kinases, PI-3 kinase, small G-proteins, microtubule-associat … More ed protein (MAP2), and cytoskeleton reorganization in HSCs cultured on type I collagen gel. Several mRNA species including SP1, BCRP, dystonin, KIF1, and KAP3B were differentially regulated by extracellular type I collagen. These results indicated that cell surface-binding to extracellular interstitial collagen may trigger intracellular signaling and alteration in gene expression of cytoskeleton-related proteins, and finally induced cytoskeleton reorganization of process elongation. Gelatin zymography of the conditioned media revealed that pro and active forms of MMP-2 was increased in the HSCs cultured on type I collagen gel but not gelatin-, or type IV collagen-coated surface or Matrigel, suggesting the importance of the native form of type I collagen fibrils in pro-MMP-2 activation. RT-PCR analysis indicated that MMP-2, MT1-MMP and TIMP-2 mRNA levels were elevated in HSCs cultured on type I collagen gel. Therefore, the native fibrillar but not monomeric form of type I collagen induced pro-MMP-2 production and activation through MT1-MMP and TIMP-2 in cultured HSCs. Less