Comparison of Human Islet Isolation Outcomes Using a New Mammalian Tissue-Free Enzyme Versus Collagenase NB-1

Background. After the discontinuation of the manufacturing Liberase HI because of a small potential for prion disease transmission, Roche Diagnostics (Indianapolis, IN) developed a new enzyme product (Liberase MTF [mammalian tissue free]), which is similar to Liberase HI with the exception that no mammalian tissue is used in the manufacture of the collagenase component. We report our experience using the MTF enzyme in clinical islet isolations compared with Serva NB-1 with modified enzyme delivery method. Methods. Islets were isolated from 41 pancreata using MTF enzyme (n=17) or NB-1 enzyme (n=24). NB-1 enzymes were delivered using a modified (nonsimultaneous) enzyme delivery method whereas isolations using MTF used the standard method of simultaneous collagenase and thermolysin perfusion. Islets were purified on a COBE 2991 Cell Blood Processor and subsequently cultured. Results. The average islet mass after purification was 392 +/- 36x10(3) islet equivalent (IE) for MTF versus 371 +/- 40x10(3) IE for Serva NB-1 (P=0.63). Post-IE/cm(3) of tissue was 110 +/- 9x10(3) IE/cm(3) and 91 +/- 11x10(3) IE/cm(3) for MTF and NB-1, respectively (P=0.07). The isolation success rate (>400,000 IE) for MTF was 53% compared with 33% for Serva (P=0.33). Conclusion. We conclude that MTF may be successfully used for high-yield human islet isolation and clinical transplantation and provides similar quality islets to those derived using NB-1.