ISLET AND PANCREAS TRANSPLANTATION I

D. O'gorman¹, T. Kin², S. Imes³, R. Pawlick⁴, P. Senior¹, J. Shapiro^3
1Clinical Islet Transplant Program, Alberta Health Services, Edmonton/CANADA, ²Clinical Islet Transplant Program, University of Alberta, Edmonton/CANADA, ³Clinical Islet Transplant Program, Alberta Health Services, Edmonton/AB/CANADA, ⁴, University of Alberta, Edmonton/CANADA

Body: Background: Islet transplantation is recognized as a viable treatment for select patients with insulin dependent diabetes mellitus. The islet isolation process can produce highly variable results which, in part, are contributed by the inconsistencies seen in the commercially available enzymes. Following the discontinuation of the manufacturing of Liberase HI ™ because of a small potential for prion disease transmission, Roche Diagnostics developed a new enzyme product, Liberase MTF. This product 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 to Serva NB-1 with modified enzyme delivery method.

Methods: Islets were isolated from 41 pancreata using either the MTF enzyme (n=17) or NB-1 (n=24) enzymes. NB-1 enzymes were delivered using a modified (non-simultaneous) enzyme delivery method while isolations using MTF utilized the standard method of simultaneous collagenase and thermolysin perfusion. Pancreata were perfused with enzyme using an automated perfusion system at 4°C and digestion of the organ was facilitated by heating a closed recirculation system to 37°C. Once a suitable number of free islets were observed under microscopy the pancreas digestion was stopped by cooling and dilution of tissue digest. Islets were purified on a modified COBE 2991 Cell Blood Processor and the subsequent purity layers were quantified to a normalized islet equivalent (IE) using a dithizone stained sample under microscopy. Islet membrane integrity was determined using fluorescence microscopy. The islet preparation was cultured at 22°C in a CMRL based media and islet isolations that met release criteria were infused intraportally. Post transplant metabolic testing was performed at one month following transplantation. Analysis of enzyme was done using anion exchange high performance liquid chromatography (HPLC).

Results: The average islet mass post purification was 392 ± 36 x 103 IE for MTF versus 371 ± 40 x 103 IE for Serva NB-1 (P= 0.63). Post-IE/cc of tissue was 110 ± 9 x 103 I.E/cc and 91 ± 11 x 103 IE/cc for MTF and NB-1 respectively (P = 0.07). The isolation success rate (> 400,000 I.E.) for MTF was 53% compared to 33% for Serva (P = 0.33). Clinical outcomes between the 2 groups were statistically similar. The insulin reduction rate was 64.6 ± 13.9% and 48.7 ± 8.8% for MTF and NB-1 respectively. The rate of insulin independence achieved 1 month following transplantation was 38% for MTF and 25% for NB-1. Results from HPLC analyses illustrate that the collagenase I (CI) fraction of the MTF had no degradation where as NB-1 analysis consistently showed a degraded CI fraction (P<0.001)

Conclusions: 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. Further studies may be required to determine the optimized enzyme dosing and delivery methods.

Disclosure: All authors have declared no conflicts of interest.