Regulation of morphology and gene expression in cultured hepatic stellate cells by three-dimensional structure of extracellular matrix

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In response to extracellular matrix (ECM) components, particularly, to interstitial collagen used as a substratum, cultured hepatic stellate cells (HSCs) exhibited a marked change in their morphology, and elongated many cellular processes resembling in vivo structure. The results from our study indicated that the induction of process elongation in cultured HSCs was dependent on cell surface integrin-binding to interstitial collagen, intracellular signaling, microtubule-associated protein 2 (MAP2), and finally microtubule reorganization. ECM components affected also proliferative ability and collagen synthesis and excretion activity, in addition to cell morphology, in cultured HSCs. Matrix metalloproteinase (MMP) expression in cultured HSCs was analyzed by in situ zymography, gelatin zymography, and reverse transcription- polymerase chain reaction (RT-PCR), suggesting the regulatory role of HSC components on the expression of MMP-1, MMP-2, MMP-13, and membrane type of MMP (MT1-MMP), as … More well as the processing of some MMPs to activated form. Thus, ECM components surrounding HSCs appear to control reorganization of basal membrane components including type TV collagen and laminin or stromal components such as type I or type III collagen at transcriptional and/or translational stages or at posttranslational processing. Since no process elongation was occurred when HSCs were cultured in type I-collagen coated dishes, HSCs seems to recognize a secondary or tertiary structure of type I collagen. However, it is not known how cells recognize the secondary or tertiary structure of type I collagen. We cultured HSCs on polystyrene surface, on type I collagen-coated surface, on type I collagen gel, or in type I collagen get, and then examined the differential expression of mRNA species depending on ECM components by using RT-PCR and differential display method. The identification of specific mRNAs expressed in HSCs cultured using type I collagen gel may leads us to clarify the mechanism by which HSCs recognize the secondary or tertiary structure of type I collagen, and are induced to express the specific mRNAs and to alter their morphology and function. Less