Studies on circulating microRNA biomarkers in dog and monkey acute pancreatic injury models

Abstract

Circulating miRNAs are promising biomarkers for pancreatic injury that potentially overcome the limitation of traditional serum enzyme biomarkers. Serum amylase and lipase have low sensitivity and specificity and do not correlate well with disease severity. This study aimed to evaluate the usefulness of four miRNAs in dog and monkey acute pancreatic injury models. Beagle dogs and Cynomolgus macaques are the most frequently used nonrodent animals in nonclinical studies. Acute pancreatic injury was induced by infusion of cerulein, a cholecystokinin analog, for 2 h (7.5 μg/kg/h) and 1 h (40 μg/kg/h) in dogs and monkeys, respectively. The levels of the well-known miRNAs, miR-216a, and miR-375, and new candidates miR-551b and miR-7 were measured at 0, 0.5, 1, 2, 6, 9, or 12, and 24 h. Serum amylase and lipase and histopathological examinations were also performed. The results of the dog study revealed that miRNAs reflect the degree of injury more sensitively than traditional biomarkers. Among the four miRNAs, miR-216a and miR-375, along with serum enzymes, were significantly increased by cerulein treatment. The expression levels of miRNAs and serum enzymes peaked at 2-6 h later with a similar pattern; however, the overall increases in the miR-216a and miR-375 levels were much higher than those of the serum enzyme biomarkers. Increased levels of miR-216a and miR-375 were most highly correlated to the degree of individual histopathological injuries of the pancreas and showed much greater dynamic response range than serum enzyme biomarkers. The results of the monkey study indicated that the overall levels of circulating miR-216a, -551b, -375, and -7 did not show a greater sensitive or larger range of response to pancreatic injury than traditional serum enzyme biomarkers. Minimal elevation of plasma miR-216a was noted in a single animal without significant changes in any other parameters. There were no significant increases of miR-375, miR-7, or miR-551b. A 24-h time-course analysis revealed time-dependent changes of miRNA expression levels from their initial increase to their decrease to pre-dose levels in acute pancreatic injury. Our findings demonstrated that in dogs, miR-216a and miR-375 have the potential to sensitively detect pancreatitis and also reveal the degree of pancreatic injury, whereas miR-551b and miR-7 do not.