Beneficial effect of recombinant rC1rC2 collagenases on human islet function: Efficacy of low‐dose enzymes on pancreas digestion and yield

A high number of human islets can be isolated by using modern purified tissue dissociation enzymes; however, this requires the use of >20 Wunsch units (WU)/g of pancreas for digestion. Attempts to reduce this dose have resulted in pancreas underdigestion and poor islet recovery but improved islet function. In this study, we achieved a high number of functional islets using a low dose of recombinant collagenase enzyme mixture (RCEM‐1200 WU rC2 and 10 million collagen‐degrading activity [CDA] U of rC1 containing about 209 mg of collagenase to digest a 100‐g pancreas). The collagenase dose used in these isolations is about 42% of the natural collagenase enzyme mixture (NCEM) dose commonly used to digest a 100‐g pancreas. Low‐dose RCEM was efficient in digesting entire pancreases to obtain higher yield (5535 ± 830 and 2582 ± 925 islet equivalent/g, P < .05) and less undigested tissue (16.7 ± 5% and 37.8 ± 3%, P < .05) compared with low‐dose NCEM (12WU/g). Additionally, low‐dose RCEM islets retained better morphology (confirmed with scanning electron microscopy) and higher in vitro basal insulin release (2391 ± 1342 and 1778 ± 978 μU/mL; P < .05) compared with standard‐dose NCEM. Nude mouse bioassay demonstrated better islet function for low‐dose RCEM (area under the curve [AUC] 24 968) compared with low‐dose (AUC–38 225) or standard‐dose NCEM (AUC–38 685), P < .05. This is the first report indicating that islet function can be improved by using low‐dose rC1rC2 (RCEM).