Gastrointestinal Pathology in Juvenile and Adult CFTR-Knockout Ferrets

Abstract

Cystic fibrosis (CF) is a multiorgan disease caused by loss of a functional cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel in many epithelia of the body. Here we report the pathology observed in the gastrointestinal organs of juvenile to adult CFTR-knockout ferrets. CF gastrointestinal manifestations included gastric ulceration, intestinal bacterial overgrowth with villous atrophy, and rectal prolapse. Metagenomic phylogenetic analysis of fecal microbiota by deep sequencing revealed considerable genotype-independent microbial diversity between animals, with the majority of taxa overlapping between CF and non-CF pairs. CF hepatic manifestations were variable, but included steatosis, necrosis, biliary hyperplasia, and biliary fibrosis. Gallbladder cystic mucosal hyperplasia was commonly found in 67% of CF animals. The majority of CF animals (85%) had pancreatic abnormalities, including extensive fibrosis, loss of exocrine pancreas, and islet disorganization. Interestingly, 2 of 13 CF animals retained predominantly normal pancreatic histology (84% to 94%) at time of death. Fecal elastase-1 levels from these CF animals were similar to non-CF controls, whereas all other CF animals evaluated were pancreatic insufficient (<2 μg elastase-1 per gram of feces). These findings suggest that genetic factors likely influence the extent of exocrine pancreas disease in CF ferrets and have implications for the etiology of pancreatic sufficiency in CF patients. In summary, these studies demonstrate that the CF ferret model develops gastrointestinal pathology similar to CF patients.

Directly Sampling the Lung of a Young Child with Cystic Fibrosis Reveals Diverse Microbiota

“…These findings support culture-based studies of children with CF (34-36) and the CF porcine and ferret models (37,38), which identified respiratory symptoms, structural lung disease, and airway inflammation in the absence of abundant "traditional CF pathogens." They also support prior lung explant studies, showing that oropharyngeal swabs did not accurately reflect the microbiota in concurrent lung samples.…”

Ferret and Pig Models of Cystic Fibrosis: Prospects and Promise for Gene Therapy

“…90,97 Interestingly, a small subset of CFTR knockout ferrets (<1%) demonstrates pancreatic sufficiency throughout life with normal weight gain and only minor exocrine damage. 91 These findings suggest that pancreatic modifier genes exist in CF ferrets, as has also been suggested in patients with CF. However, the exocrine pancreas of most CFTR knockout ferrets undergoes rapid destruction over the first month of life, leading to extensive fibrosis, loss of exocrine pancreas, islet remodeling, and diabetes.…”

“…However, the exocrine pancreas of most CFTR knockout ferrets undergoes rapid destruction over the first month of life, leading to extensive fibrosis, loss of exocrine pancreas, islet remodeling, and diabetes. 91,97 Both CF ferrets and pigs also show abnormalities in insulin secretion at birth, 97,98 suggesting that abnormal islet function initiates early in CF. Because CF ferret and pig models have differing degrees of exocrine disease severity at birth, they present opportunities to test CF gene therapies that target early and late disease processes, respectively.…”

“…Malnutrition and distal intestinal obstruction syndrome in older CF ferrets and pigs is similar to that observed in patients with CF. 91,92 The creation of gut-corrected CFTR knockout ferrets and pigs harboring a wild-type CFTR transgene under the direction of the fatty acid-binding promoter will be useful models with reduced intestinal pathologies. 90,92 Furthermore, gutcorrected CFTR knockout models provide the opportunity to test gene therapies without the potential complication of developing cellular immunity against the CFTR transgene.…”

Origins of Cystic Fibrosis Lung Disease

“…A similar gene targeting strategy was used to produce ferrets lacking CFTR 21 . They develop characteristic features of human cystic fibrosis including intestinal, pancreatic, and airway disease, and they may be particularly valuable for studying cystic fibrosis-related diabetes mellitus 21,[31][32][33][34] . Cystic fibrosis rats, recently produced using zinc finger endonuclease technology, develop intestinal, airway and reproductive features consistent with human disease 22 .…”