Assessment of a novel two-component enzyme preparation for human islet isolation and transplantation

Background. Biologic characteristics of enzyme products used for islet isolation are critical for the success of islet transplantation. In particular, lot-to-lot variability significantly affects the yields of the isolation procedure. In this study, we have evaluated a new enzyme preparation in which highly purified collagenase can be blended with separately supplied neutral protease in a predetermined ratio. Methods. We compared the results of human-islet isolations performed either with Collagenase NB1 supplemented with Neutral Protease NB (group I, n = 9) or with Liberase (group II, n = 9). Results. Endotoxin contents of the enzyme preparations were lower in group I. Total islet yields were similar in both groups, but islet equivalents per gram of pancreas was higher in group I (4,020 +/- 1,240 vs. 2,360 +/- 1,350; P < 0.05). Islet morphology was improved in group I with significantly higher proportion of free and intact islets (71 +/- 9% vs. 52 +/- 14%; P < 0.01). In vitro function was improved and apoptosis rate was lower in group I. Conclusions. This new enzyme blend was as efficient as Liberase in terms of islet yields and showed improvements in islet morphology, viability, and in vitro function. The possibility to control lot-to-lot variability, and the low endotoxin contents make Collagenase NB1 a promising product for human-islet isolation.