Prevention of central cell damage to isolated islets of Langerhans in hamsters by low temperature preconditioning

BACKGROUND: The efficacy of clinical islet transplanta- tion has been demonstrated with autografts, and although islet allografts have established insulin independence in a small number of IDDM patients, the treatment is con- founded by the necessity of central cell damage immuno- suppression, the lack of donor tissue, and recurring islet immunogenicity. These limitations underscore a need to develop therapies to serve the large population of diabetic patients. This study was designed to document central cell damage to isolated islets of Langerhans in hamsters and its prevention. METHODS: Islets were cultured at 37 °C for 7-14 days after isolation, and then at 26 °C for 2,4 and 7 days before addi- tional culture at 37 °C for an additional 7 days. Central cell damage in the isolated islets was monitored by video-mi- croscopy and analyzed quantitatively by a computer-assis- ted image analysis system. The analysis included daily measurement of the diameter and the area of the isolated is- lets and the area of the central cell damage that developed in those islets over time during culture. Histological exami- nation and TdT-mediated dUTP-biotin nick end labeling (TUNEL) assay were used to characterize cell damage and to monitor islet function. RESULTS; Microscopic analysis showed that during the 7 to 14 days of culture at 37 °C, central cell damage appeared in the larger islets with diameters greater than 200 μm, which included both necrotic and apoptotic cell death. Low temperature (26 °C) culture prevented central cell damage of isolated islets. The 7-day culture procedure at 26 °C could inhibit most of the central cell ( excluding diameters greater than 300 μm) damage when the islets were re- warmed to 37 °C. CONCLUSIONS: Our results indicate that central cell da- mage to isolated islets of Langerhans correlates with the size of the islets. Low temperature (26 °C) culture can preventcentral cell damage to the isolated islets, and is capable to successfully precondition these islets for 37 °C culture. These novel findings may help to understand the patho- physiology of early loss of islet tissue after transplantation, and may provide a new strategy to improve graft function in the clinical setting of islet transplantation.

Apoptosis and oxidative injury of donor islets during isolation and purification

Objective To observe the changes of islet cell apoptosis and oxidation - antioxidation before transplantation,and to explore pathways of islet protection. Methods Fifteen human pancreases were perfused with Hanks solution containing collagenase,then digested and isolated.

Testing of a New Collagenase Blend for Pancreatic Islet Isolation Produced by Clostridium histolyticum

Clostridium histolyticum is used for production of several proteolytic enzymes such as elastase, neutral proteases, clostripain and in particular collagenase. Besides industrial applications, collagenase has been indispensable for medical purposes including isolation of pancreatic islets for diabetes treatment. The aim of this study was to optimize the method for production and partial purification of a new collagenase blend and to test its suitability for successful pancreatic islets isolation in a rat model. Bacterial strain of C. histolyticum was sequenced for presence of the collagenase genes. Different fermentation conditions were tested and the process of collagenase extraction was modified and optimized. Samples of collagenases were taken for western blot detection, activity assessment, and ability for dissociation of pancreatic tissue. Findings indicate that concentrated trypton growth medium with pepton was the most suitable for Clostridium growth and collagenase production. Whole genome sequencing revealed two genes for collagenase and also gene for clostripain. Western blot specific detection helped to select useful production modifications. Following these modifications was also improved the yield, morphology and in vitro function of intact pancreatic islets which were finally comparable or better than those achieved using standard blends of collagenase. The results support the use of the new collagenase blend for islet isolation giving thus the opportunity to choose an alternative product. Our next steps would lead to further enzyme purification through scaling up of the production method for a wider use.