Wirz W, Antoine M, Tag C G, Gressner A M, Korff T, Hellerbrand C, Kiefer P
Institute of Clinical Chemistry and Pathobiochemistry, RWTH Aachen, D-52073 Germany.
Differentiation. 2008 Sep;76(7):784-94. doi: 10.1111/j.1432-0436.2007.00260.x. Epub 2008 Jan 3.
Hepatic stellate cells (HSCs) are pericytes of liver sinusoidal endothelial cells (LSECs) and activation of HSC into a myofibroblast-like phenotype (called transdifferentiation) is involved in several hepatic disease processes including neovascularization during liver metastasis, chronic and acute liver injury. While early smooth muscle cell (SMC) differentiation markers including SM alpha-actin and SM22alpha are expressed in a variety of non-SMC, expression of late-stage markers is far more restricted. Here, we found that in addition to early SMC markers, activated rat HSC express a large panel of characteristic late vascular SMC markers including SM myosin heavy chain, h1-calponin and h-caldesmon. Furthermore, myocardin, which is present exclusively in SMCs and cardiomyocytes and controls the transcription of a subset of early and late SMC markers, is highly expressed in activated HSC. We further studied activated HSC in a functional three-dimensional spheroidal co-culture system together with endothelial cells (EC). Co-culture spheroids of EC and SMC differentiate spontaneously and organize into a core of SMC and a surface layer of EC representing an inside-outside model of the physiological assembly of blood vessels. Replacing SMC by in vitro activated HSC resulted in a similar organized spheroid with differentiated, von-Willebrand factor producing, surface lining quiescent human umbilical vein endothelial cell and a core of HSC. In an in vitro angiogenesis assay, activated HSC induced quiescence in vascular EC-the hallmark of vascular SMC function. Co-spheroids of LSEC and activated HSC formed capillary-like sprouts in gel angiogenesis assays expressing the vascular EC marker VE-cadherin. Our findings indicate that activated HSC are capable to adapt a functional SMC phenotype and to induce formation of tubular sprouts by LSEC and vascular endothelial cells. Since tumors and tumor metastasis induce HSC activation, HSC may take part in tumor-induced neoangiogenesis by adapting SMC-like functions.
肝星状细胞（HSCs）是肝窦内皮细胞（LSECs）的周细胞，HSC激活转变为肌成纤维细胞样表型（称为转分化）参与了多种肝脏疾病过程，包括肝转移过程中的新生血管形成、慢性和急性肝损伤。虽然早期平滑肌细胞（SMC）分化标志物，如平滑肌α-肌动蛋白和SM22α，在多种非SMC中表达，但晚期标志物的表达则更为局限。在此，我们发现，除了早期SMC标志物外，活化的大鼠HSC还表达大量特征性的晚期血管SMC标志物，包括平滑肌肌球蛋白重链、h1-钙调蛋白和h-钙调蛋白。此外，仅存在于SMC和心肌细胞中并控制早期和晚期SMC标志物子集转录的心肌转录因子，在活化的HSC中高度表达。我们进一步在功能性三维球体共培养系统中，将活化的HSC与内皮细胞（EC）一起进行研究。EC和SMC的共培养球体可自发分化，并组织形成一个SMC核心和一层EC表面层，代表血管生理组装的由内而外模型。用体外活化的HSC替代SMC，可产生类似的有组织的球体，其表面衬有分化的、产生血管性血友病因子的静止人脐静脉内皮细胞，核心为HSC。在体外血管生成试验中，活化的HSC诱导血管EC静止，这是血管SMC功能的标志。LSEC和活化HSC的共球体在表达血管EC标志物血管内皮钙黏蛋白的凝胶血管生成试验中形成毛细血管样芽。我们的研究结果表明，活化的HSC能够适应功能性SMC表型，并诱导LSEC和血管内皮细胞形成管状芽。由于肿瘤和肿瘤转移会诱导HSC活化，HSC可能通过发挥类似SMC的功能参与肿瘤诱导的新生血管形成。
