Engraftment of islets obtained by collagenase and liberase in diabetic rats: A comparative study

Introduction: Islet transplantation is an attractive solution for type I di abetes, but the results are at the present discouraging. Collagenase. the e nzyme used to obtain islets for transplantation, presents interbatch variab ility and endotoxin contamination that induces inflammatory cytokine produc tion. Liberase (Roche. Basel, Switzerland), a new mixture of purified enzym es, has the same composition in all batches and is endotoxin-free. Aims: To compare the engraftment of islets obtained using either enzyme in streptozotocin-induced diabetic rats. Methodology: Collagenase- or Liberase- isolated islets were transplanted un der the kidney capsule of diabetic rats. Collagenase islets restored glycem ia and insulinemia in all animals 24 hours, and both parameters were mainta ined in 45% of rats over 90 days; however, Liberase islets failed to revers e diabetes in all subjects. Results: In vitro experiments showed that Liberase islets did not maintain active insulin secretion. Cytotoxicity assays showed toxicity of Liberase t o islets: both enzymes induced inflammatory cytokine production by macropha ges. Conclusion: In summary, in our model, Liberase is not a good substitute for collagenase as an islet-isolating reagent. A major effort and investment i n developing enzymes for tissue dispersion is needed to improve the outcome of islet transplantation.