Project description:The liver is a central organ for metabolism and hepatocytes are the main cell type responsible for most of its functions. Several previous studies investigated the cell types involved in tissue homeostasis and regeneration, however, the mechanisms underlying post-natal liver growth and establishment of the mature hepatocyte phenotypes remain to be fully understood. Here we investigate liver tissue dynamics in mice during growth and adulthood, by spatial transcriptomics, clonal analysis, and lineage tracing. We observe the progressive establishment of metabolic zonation of hepatocytes following weaning, with the specification of the centrilobular identity only in adults. We report that only a fraction of hepatocytes proliferate in the newborn liver, generating most of the adult tissue, and that preferential gene editing of the more proliferating hepatocytes allows expansion of the genetically engineered liver area. We also describe age-dependent differences in the efficiency and distribution of lentiviral in vivo gene delivery, with higher efficiency of gene transfer in young compared to adult animals and a skewed localization within the liver lobule. We identify high proteasome activity in the peri-central lobular area as the major determinant of the observed outcome and successfully revert it by proteasomal inhibition before vector administration. Overall, our findings provide new insights into the spatiotemporal dynamics of hepatocytes during post-natal growth, which extend our understanding of liver biology and have important implications for therapeutic applications.
Project description:The liver is a central organ for physiology and metabolism, with hepatocytes being the main cell type responsible for most of its functions. Several previous studies investigated the cell types involved in tissue homeostasis and regeneration, however the mechanisms underlying post-natal liver growth and establishment of the mature hepatocyte phenotypes remain to be fully understood. Moreover, genetic modification of hepatocytes is emerging as a promising therapeutic approach, particularly for genetic diseases of the coagulation system and hepatic metabolism. Here, we investigate liver tissue dynamics in mice during post-natal growth and turnover in adulthood, by spatial transcriptomics, clonal analysis, and lineage tracing. We observe progressive establishment of metabolic zonation of hepatocytes and that only a fraction of hepatocytes proliferates in the newborn liver, generating most of the adult tissue. We assess the impact of these changes on both in vivo liver gene transfer and gene editing. We show that the age at treatment affects both the efficiency and lobule distribution of lentiviral vector-mediated gene transfer, and that preferential targeting of the more proliferating hepatocytes allows expansion of the genetically modified liver area. Overall, our findings provide new insights into the spatio-temporal dynamics of the liver during post-natal growth and hepatocyte heterogeneity, with broad implications for liver biology and therapeutic applications.
Project description:Liver regeneration is an extraordinarily complex process involving a variety of factors; however, the role of chromatin protein in hepatocyte proliferation is largely unknown. In this study, we investigated the functional role of high-mobility group box 2 (HMGB2), a chromatin protein in liver regeneration using wild-type and HMGB2-knockout (KO) mice. Liver tissues were sampled after 70% partial hepatectomy (PHx), and analyzed by immunohistochemistry using various markers of cell proliferation, including Ki-67, PCNA, cyclin D1, cyclin B1, EdU and pH3S10. In WT mice, hepatocyte proliferation was strongly correlated with the spatiotemporal expression of HMGB2; however, cell proliferation was significantly delayed in hepatocytes of HMGB2-KO mice. Quantitative PCR demonstrated that cyclin D1 and cyclin B1 mRNAs were significantly decreased in HMGB2-KO mice livers. Interestingly, hepatocyte size was significantly larger in HMGB2-KO mice at 36-72 h after PHx, and these results suggest that hepatocyte hypertrophy appeared in parallel with delayed cell proliferation. In vitro experiments demonstrated that cell proliferation was significantly decreased in HMGB2-KO cells. A significant delay in cell proliferation was also found in HMGB2-siRNA transfected cells. In summary, spatiotemporal expression of HMGB2 is important for regulation of hepatocyte proliferation and cell size during liver regeneration.
Project description:Cholestatic injuries, featured with regional damage around the periportal, cause considerable mortality without curative therapies. It is technically challenging to dissect regional cell-cell interactions and molecular changes to fully understand cholangiopathies. Here, we generated a high-definition atlas of spatiotemporal transcriptome during cholestatic injury and repair. Remarkably, cholangiocytes functioned as a periportal hub by integrating signals from neighboring cells. We also dissected periportal damage, spatial heterogenous reprogramming and zonal regeneration, which appeared to be strongly associated with cholangiocyte. Moreover, spatiotemporal analyses revealed a key inhibitory rheostat for hepatocyte proliferation. Together, our study provides a comprehensive resource that is instrumental to demarcate regional cholestatic injury.