Islet transplantation is a method for the treatment of type 1 diabetes mellitus (DM) and has been widely performed around the world. The long-term cryopreservation of islets shows many advantages in the field of islet transplantation. Previous studies have described the development of sheet-type polyvinyl alcohol (PVA) macro-encapsulated islets (MEI) to treat type 1 DM without any immunotherapy. The present study examined their beneficial effects on islet cryopreservation. PVA MEI of Wistar rats were divided into three groups of 1-day, 7-day and 30-day cryopreservation at -80 degrees C. The 30-day group showed a lower recovery rate of the islet number and impaired insulin release in comparison to the 1-day group, whereas no significant differences of the in vitro results were observed between the 1-day and 7-day groups. The MEI transplantation recipient mice in the 1-day and 7-day groups reached normoglycemia for a 4-week observation period, and the recipients in 30-day group also showed a significant decrease followed by a slightly higher non-fasting blood glucose level. These results suggest that the PVA MEI are useful for islet long-term cryopreservation, and that the use of cryopreserved PVA MEI may, therefore, be a promising modality for performing DM therapy.
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