BACKGROUND: The efficacy of clinical islet transplantation has been demonstrated with autografts, and although islet allografts have established insulin independence in a small number of IDDM patients, the treatment is confounded by the necessity of central cell damage immunosuppression, 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 ℃ for 7-14 days after isolation, and then at 26 ℃ for 2,4 and 7 days before additional culture at 37 ℃ for an additional 7 days. Central cell damage in the isolated islets was monitored by video-microscopy and analyzed quantitatively by a computer-assisted image analysis system. The analysis included daily measurement of the diameter and the area of the isolated islets and the area of the central cell damage that developed in those islets over time during culture. Histological examination 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 ℃, 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 ℃) culture prevented central cell damage of isolated islets. The 7-day culture procedure at 26 ℃ could inhibit most of the central cell (excluding diameters greater than 300 μm) damage when the islets were rewarmed to 37 ℃.
CONCLUSIONS: Our results indicate that central cell damage to isolated islets of Langerhans correlates with the size of the islets. Low temperature (26 ℃) culture can prevent central cell damage to the isolated islets, and is capable to successfully precondition these islets for 37 ℃ culture. These novel findings may help to understand the pathophysiology 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.