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Abstract Background Pancreatic fibrosis is an early diagnostic feature of the common inherited disorder cystic fibrosis (CF). Many people with CF (pwCF) are pancreatic insufficient from birth and the replacement of acinar tissue with cystic lesions and fibrosis is a progressive phenotype that may later lead to diabetes. Little is known about the initiating events in the fibrotic process though it may be a sequela of inflammation in the pancreatic ducts resulting from loss of CFTR impairing normal fluid secretion. Here we use a sheep model of CF (CFTR −/− ) to examine the evolution of pancreatic disease through gestation. Methods Fetal pancreas was collected at six time points from 50-days of gestation through to term, which is equivalent to ~ 13 weeks to term in human. RNA was extracted from tissue for bulk RNA-seq and single cells were prepared from 80-day, 120-day and term samples for scRNA-seq. Data were validated by immunochemistry. Results Transcriptomic evidence from bulk RNA-seq showed alterations in the CFTR −/− pancreas by 65-days of gestation, which are accompanied by marked pathological changes by 80-days of gestation. These include a fibrotic response, confirmed by immunostaining for COL1A1, αSMA and SPARC, together with acinar loss. Moreover, using scRNA-seq we identify a unique cell population that is significantly overrepresented in the CFTR −/− animals at 80- and 120-days gestation, as are stellate cells at term. Conclusion The transcriptomic changes and cellular imbalance that we observe likely have pivotal roles in the evolution of CF pancreatic disease and may provide therapeutic opportunities to delay or prevent pancreatic destruction in CF.

Abstract Highly effective modulator therapies for cystic fibrosis (CF) make it a treatable condition for many people. However, although CF respiratory illness occurs after birth, other organ systems particularly in the digestive tract are damaged before birth. We use an ovine model of CF to investigate the in utero origins of CF disease since the sheep closely mirrors critical aspects of human development. Wildtype (WT) and CFTR ‐/‐ sheep tissues were collected at 50, 65, 80, 100, and 120 days of gestation and term (147 days) and used for histological, electrophysiological, and molecular analysis. Histological abnormalities are evident in CFTR‐/‐ ‐/‐ animals by 80 days of gestation, equivalent to 21 weeks in humans. Acinar and ductal dilation, mucus obstruction, and fibrosis are observed in the pancreas; biliary fibrosis, cholestasis, and gallbladder hypoplasia in the liver; and intestinal meconium obstruction, as seen at birth in all large animal models of CF. Concurrently, cystic fibrosis transmembrane conductance regulator (CFTR)‐dependent short circuit current is present in WT tracheal epithelium by 80 days gestation and is absent from CFTR ‐/‐ tissues. Transcriptomic profiles of tracheal tissues confirm the early expression of CFTR and suggest that its loss does not globally impair tracheal differentiation.