The role of the Interleukin-6 receptor in liver damage and regeneration

免疫应答和肝损伤/再生的干扰是由白细胞介素（IL-）6家族的细胞因子控制的。最近，我们已经证明主要是IL-6反式信号直接或间接地促进肝细胞增殖，并足以在肝部分切除术（PHX）后肝再生。除IL-6外，其他IL-6型细胞因子包括IL-11、OSM和LIF也影响肝脏再生。在本研究项目中，我们将利用多种转基因小鼠模型揭示IL-6通路在PHX后肝脏再生过程中的细胞类型特异性贡献。首先，我们将分析在PHX期间肝脏中哪些细胞类型表达IL-6型细胞因子及其受体，包括IL-6， IL-11， OSM和LIF。由于IL-6R缺陷小鼠具有肝脏再生功能障碍，因此这些细胞因子在PHX后挽救这种表型的潜力将被确定。此外，我们将确定在PHX后肝脏再生过程中IL-6信号传导的靶细胞。为此，将在肝细胞、肝星状细胞、巨噬细胞或T细胞中显示组织特异性条件IL-6R缺乏的小鼠中监测PHX后的肝脏再生。反之亦然，将使用L-gp130和GVHH-gp130的组织特异性表达来研究功能获得。L-gp130是一种合成的不依赖配体的组成型活性gp130受体变体，能够启动和维持细胞自主IL-6信号转导。GVHH-gp130是一种可切换的合成gp130细胞因子受体，可被二聚体GFP（绿色荧光蛋白）配体激活。对于GVHH-gp130，我们将通过注射重组同源二聚体GFP融合蛋白诱导合成IL-6信号，确定IL-6信号的最佳再生时间窗。L-gp130和GVHH-gp130在转基因小鼠中与表达Cre-recombinase的小鼠杂交后启动表达，有利于在肝细胞、肝星状细胞、巨噬细胞或T细胞中进行组织特异性表达。将这些小鼠杂交到IL-6R缺乏的背景下，在监测PHX后的肝脏再生之前，禁用内源性天然IL-6信号。该分析将允许表征il -6依赖性，再生能力的细胞类型的肝脏在损伤和再生阶段。该项目旨在利用常见的功能丧失和新型功能获得转基因小鼠模型，阐明目前未知的IL-6在PHX后肝脏再生中的细胞类型特异性功能。

The interference of immune response and liver damage/-regeneration is controlled by cytokines of the Interleukin (IL-)6 family. Recently, we have demonstrated that mainly IL-6 trans-signalling directly and indirectly promotes hepatocyte proliferation and is sufficient for liver regeneration following partial hepatectomy (PHX). In addition to IL-6, other IL-6 type cytokines including IL-11, OSM and LIF affect liver regeneration. In this research project, we will unravel the cell-type specific contribution of IL-6 pathways during liver regeneration following PHX using a variety of transgenic mouse models. First of all, we will analyze which cell types of the liver express IL-6 type cytokines and their receptors during PHX including IL-6, IL-11, OSM, and LIF. Since IL-6R deficient mice have a disfunctional liver regeneration, the potential to rescue this phenotype by these cytokines following PHX will be determined. Moreover, we will define the target cells of IL-6 signalling during liver regeneration following PHX. To this end, liver regeneration after PHX will be monitored in mice displaying a tissue specific conditional IL-6R deficiency in hepatocytes, hepatic stellate cells, macrophages, or T cells. Vice versa gain-of-function will be studied using tissue specific expression of L-gp130 and GVHH-gp130. L-gp130 is a synthetic ligand-independent, constitutive active gp130 receptor variant, which is able to initiate and maintain cell-autonomous IL-6 signal transduction. GVHH-gp130 is a switchable synthetic gp130 cytokine receptor, which can be activated by dimeric GFP (green fluorescent protein)-ligands. For GVHH-gp130, we will induce synthetic IL-6 signalling by injection of recombinant homodimeric GFP fusion proteins, to determine the optimal regenerative time window of IL-6 signalling. Expression of L-gp130 and GVHH-gp130 in transgenic mice will be initiated after crossing to Cre-recombinase expressing mice, which facilitates tissue specific expression in hepatocytes, hepatic stellate cells, macrophages, or T cells. These mice will be crossed onto the IL-6R deficient background to disable endogenous, natural IL-6 signalling before monitoring the liver regeneration following PHX. This analysis will allow the characterization of IL-6-dependent, regeneration competent cell types of the liver during the damage and regeneration phases. The project aims to elucidate the currently unknown cell-type specific function of IL-6 in liver regeneration following PHX using/employing common loss-of-function and novel gain-of-function transgenic mouse models.