Most reports show that at best, about 48% of the human islet isolations yield a sufficient number of islets for subsequent transplantation. Recently, Balamurugan and colleagues at the University of Minnesota’s Schulze Diabetes Institute showed that this percentage could be increased to > 75% by selecting the appropriate mixture of enzymes. The key to the UMN success was using a “new enzyme mixture” containing VitaCyte’s CIzyme Collagenase HA and Serva’s NB neutral protease.
The effectiveness of the new enzyme mixture was initially shown by comparing the new enzyme mixture’s performance (n=4) to enzyme mixtures that contained purified collagenase and thermolysin either Roche or VitaCyte (n=47) or purified collagenase and C. histolyticum neutral protease (CHNP) from Serva (n=25)1. A direct comparison of the performance of thermolysin and CHNP in human islet isolation was made using a split human pancreas and digesting each side with an optimal dose of CIzyme Collagenase HA and thermolysin or the same dose of HA and an optimal dose of CHNP. The results from these experiments showed that higher islets yields (IEQ/g tissue) were obtained with the new enzyme mixture but this result was not statistically significant (p = 0.06). However, the new enzyme mixture was found to provide significantly superior yields (n=18) when compared to islets isolated with Serva NB-1 collagenase/NB neutral protease (n=36) or VitaCyte’s CIzyme Collagenase HA/Thermolysin (n=40).
A key element of these observations is the use of purified class I (C1) and class II (C2) collagenase where a large proportion of the C1 is intact, containing both collagen binding domains. An open question raised from these results is the reasons why CHNP was more effective than thermolysin. Serva’s NB CHNP is heterogeneous and has a specific neutral protease activity of about 15,000 NP U/mg as compared with much higher specific neutral protease activity for other purified bacterial neutral proteases (e.g, > 85,000 NP U/mg protein for BP Protease). This led VitaCyte to develop a highly purified CHNP that has an enhanced specific NP activity is in excess of 150,000 NPU/per mg. This product will be offered soon commercially. If there is interest to obtain samples for evaluation, please contact VitaCyte at 317-917-3547, 888-664-2687 or by e mail at firstname.lastname@example.org.
1. A.N.Balamurugan, G. Loganathan, et al. (2010) A New Enzyme Mixture to Consistently Achieve High Human Islet Yield and Improved Allogenic and Autograft Islet Transplantation Outcome. XXIII International Congress of the Transplantation Society, Vancouver, Canada. MO21.03