Dynamic scRNA-seq of live human pancreatic slices reveals functional endocrine cell neogenesis through an intermediate ducto-acinar stage.

Human pancreatic plasticity is implied from multiple single-cell RNA sequencing (scRNA-seq) studies. However, these have been invariably based on static datasets from which fate trajectories can only be inferred using pseudotemporal estimations. Furthermore, the analysis of isolated islets has resulted in a drastic underrepresentation of other cell types, hindering our ability to interrogate exocrine-endocrine interactions. The long-term culture of human pancreatic slices (HPSs) has presented the field with an opportunity to dynamically track tissue plasticity at the single-cell level. Combining datasets from same-donor HPSs at different time points, with or without a known regenerative stimulus (BMP signaling), led to integrated single-cell datasets storing true temporal or treatment-dependent information. This integration revealed population shifts consistent with ductal progenitor activation, blurring of ductal/acinar boundaries, formation of ducto-acinar-endocrine differentiation axes, and detection of transitional insulin-producing cells. This study provides the first longitudinal scRNA-seq analysis of whole human pancreatic tissue, confirming its plasticity in a dynamic fashion.

Endothelial c-Myc knockout enhances diet-induced liver inflammation and fibrosis.

Endothelial cells play an essential role in inflammation through synthesis and secretion of chemoattractant cytokines and expression of adhesion molecules required for inflammatory cell attachment and infiltration. The mechanisms by which endothelial cells control the pro-inflammatory response depend on the type of inflammatory stimuli, endothelial cell origin, and tissue involved. In the present study, we investigated the role of the transcription factor c-Myc in inflammation using a conditional knockout mouse model in which Myc is specifically deleted in the endothelium. At a systemic level, circulating monocytes, the chemokine CCL7, and the extracellular-matrix protein osteopontin were significantly increased in endothelial c-Myc knockout (EC-Myc KO) mice, whereas the cytokine TNFSF11 was downregulated. Using an experimental model of steatohepatitis, we investigated the involvement of endothelial c-Myc in diet-induced inflammation. EC-Myc KO animals displayed enhanced pro-inflammatory response, characterized by increased expression of pro-inflammatory cytokines and leukocyte infiltration, and worsened liver fibrosis. Transcriptome analysis identified enhanced expression of genes associated with inflammation, fibrosis, and hepatocellular carcinoma in EC-Myc KO mice relative to control (CT) animals after short-exposure to high-fat diet. Analysis of a single-cell RNA-sequencing dataset of human cirrhotic livers indicated downregulation of MYC in endothelial cells relative to healthy controls. In summary, our results suggest a protective role of endothelial c-Myc in diet-induced liver inflammation and fibrosis. Targeting c-Myc and its downstream pathways in the endothelium may constitute a potential strategy for the treatment of inflammatory disease.