Liver regeneration is a clinically important tissue repair process in which the liver responds to injury by driving a synchronized replication of differentiated liver cells. The process involves the interplay of carefully orchestrated signals frm different cell types integrated with systemic factors to recover functional tissue mass. Liver regeneration is inhibited by chronic ethanol consumption and this impaired repair response may contribute to the risk for alcoholic liver disease. The mechanisms responsible for the onset and progression of the regenerative response and its deregulation by ethanol remain poorly characterized. In prior studies we carried out a detailed gene expression and microRNA profiling study of the regeneration response after 70% partial hepatectomy (PHx) in ethanol-fed and control rats and developed novel bioinformatics tools to highlight cell- type specific transcriptomic signatures. These studies indicate that chronic ethanol treatment affects non- parenchymal cells (NPCs) that control hepatocyte priming and replication and is associated with upregulation of a hepatic stellate cell (HSC) activation signature. We obtained evidence that miR-21 may be a driver of these differential responses. Inhibition of miR-21 in the rat in vivo by treatment with AM21, a specific miR-21 antagonist, allowed recovery of liver regeneration in ethanol-fed rats while suppressing the differential HSC activation profile. In the current application we build on these findings to analyze how different cell types contribute to the integrated tissue response using laser capture microdissection (LCM) and integrating the experimental data through a computational modeling approach to predict how regeneration is inhibited by adaptation to chronic ethanol exposure and rescued by miR-21 inhibition. (1) We will analyze the temporal regeneration dynamics in ethanol-fed and control rats and profile the differential impact of AM21 treatment to characterize the miR-21 target processes that contribute to the ethanol-mediated inhibition of liver regeneration, with a focus on the contribution of NPCs to cell cycle progression. We will further compare rat and mouse models of liver regeneration to evaluate how miR-21's interactions with cell cycle regulators differs in animals that have a different temporal response to PHx. (2) We will test the hypothesis that the adaptation to ethanol consumption alters the temporal response of different cell types in the liver, deregulating the integrated tissue response, by analyzing cell type-specific changes in the transcriptome and microRNA expression in ethanol-fed animals compared to controls by analyzing individual cells obtained using LCM. (3) We will apply a computational model of the role of cell-type specific interactions in liver regeneration to iteratively evaluate the consequences of dynamic changes in phenotype distribution. Our integrated experimental and computational analysis will yield new insights into the regulatory miRNA network driving cell phenotype distributions and cell-cell interactions, and the mechanisms through which interventions in these networks can counter ethanol-induced suppression of liver repair, with applications to translational and clinical interventions i in a broad range of liver diseases.
Liver regeneration is a clinically important tissue repair mechanism inhibited by chronic alcohol consumption and this impaired repair response may contribute to the risk for alcoholic liver disease. This project combines experimental and computational modeling analyses to test the hypothesis that the defective liver regeneration in alcohol-treated animals is associated with activation of hepatic stellate cells mediated by a microRNA regulatory network involving miR-21.
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