9.6 - Single-cell spatial transcriptomics analysis of a regenerating liver

Satdarshan Monga (University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center), Sungjin Ko (University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center), Shikai Hu (University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center), Sucha Singh (University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center), Minakshi Poddar (University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center)

Liver, the largest gland in the body performs more than 500 functions. It is comprised of lobules, which are the functional metabolic units formed by a central vein in the center, and multiple portal triads at the periphery. Each portal triad is composed of a portal vein, hepatic artery and bile duct. Blood enters the lobule through portal vein and hepatic artery and moves through sinusoids that are lined by the sinusoidal endothelial cells (LSECs) and eventually exits through the central vein. Hepatocytes line the other side of the endothelial cells along the porto-central axis. Intriguingly, the hepatocytes located across the lobule express genes differently based on their proximity to portal triad (zone-1) versus central vein (zone-3). This process of metabolic zonation ensures division of labor making hepatocytes more efficient in performing their endowed functions of synthesis, metabolism and detoxification based on their location in specific zones. Recent studies have begun to show that zonation of gene expression exists not only in hepatocytes but also in other minority cell types of the liver including cholangiocytes, endothelial cells, macrophages and stellate cells. Liver is also a unique organ with an innate capability to regenerate following toxicant-induced injury or surgical resection. The process of regeneration is ensured by replication of all surviving cells in the liver. Very little is known about how metabolic zonation changes during the process of regeneration and how the various functions performed by the liver are maintained while the hepatocytes and other cells undergo replication towards attaining the pre-hepatectomy mass. Here, we perform Molecular CartographyTM, a single cell spatial transcriptomics technique, to address changes in the both the expression and location of both zonated and non-zonated genes in various cell types of the liver following partial hepatectomy. We address how these one hundred carefully selected genes undergo dynamic regulation as cells in the remnant liver attempt to maintain both function and proliferate to restore liver mass. In our current study we identify dynamic changes in spatiotemporal regulation of multiple important genes associated with most proliferation and function of cells during the process of liver regeneration.