Continuous clonal labeling reveals uniform progenitor potential in the adult exocrine pancreas

The tissue dynamics that govern maintenance and regeneration of the pancreas remain largely unknown. In particular, the presence and nature of a cellular hierarchy remains a topic of debate. Previous lineage tracing strategies in the pancreas relied on specific marker genes for clonal labeling, which left other populations untested and failed to account for potential widespread phenotypical plasticity. Here we employed a tracing system that depends on replication-induced clonal marks. We found that in homeostasis, steady acinar replacement events characterize tissue dynamics, to which all acinar cells have an equal ability to contribute. Similarly, regeneration following pancreatitis was best characterized by an acinar self-replication model, as no evidence for a cellular hierarchy was detected. In particular, rapid regeneration in the pancreas was found to be driven by an accelerated rate of acinar fission-like events. Together these results provide a comprehensive and quantitative model of cell dynamics in the exocrine pancreas. Examination of single cell RNA expression profiles of labeled and non-labeled pancreatic cells during homeostasis and during cerulein-induced pancreatitis (9DPI)