We newly developed a sheet-type macroencapsulation device entrapping rat islets from 3% polyvinyl alcohol (PVA) dissolved in Euro-Collins solution containing 10% fetal bovine serum and 5% dimethyl sulfoxide (PVA + EC) using a freezing/thawing technique. The same encapsulation technique but with 3% PVA dissolved only in double-distilled water (PVA) and a culture of free islets were served as controls. After 14-day culture in the CMRL-1066 medium, the islet recovery rate, morphological changes, insulin content, and insulin secretion were evaluated in vitro to prove the feasibility of this method of encapsulation. We also xenotransplanted the device into the peritoneal cavity of diabetic C57BL/6 mice to check its function in vivo. After 1-day culture, the islet recovery rate and insulin content in the PVA group were significantly lower than that in the PVA + EC and free islet groups. After 14-day culture, only the islets in the PVA+EC group maintained a normal morphology and effective insulin secretory response to high glucose while the response was not observed in the PVA group after 1-day culture and no longer observed in the free islets after 7-day culture. After transplantation of rat islets encapsulated in the PVA + EC device to diabetic C57BL/6 mice, nonfasting blood glucose levels showed a rapid decrease from high glucose levels of pre-transplantation, maintaining significantly lower glucose levels during the whole course of study in comparison with the sham-operated group. Our results indicated that this freezing/thawing macroencapsulation technique using 3% PVA + EC was effective for xenotransplantation of islet cells.

Islet transplantation is a minimally invasive treatment for severe diabetes. However, it often requires multiple donors to accomplish insulin-independence and the long-term results are not yet satisfying. Therefore, novel ways to overcome these problems have been explored. Isolated islets are fragile and susceptible to pro-apoptotic factors and poorly proliferative. In contrast, mesenchymal stem cells (MSCs) are highly proliferative, anti-apoptotic and pluripotent to differentiate toward various cell types, promote angiogenesis and modulate inflammation, thereby studied as an enhancer of islet function and engraftment. Electrofusion is an efficient method of cell fusion and nuclear reprogramming occurs in hybrid cells between different cell types. Therefore, we hypothesized that electrofusion between MSC and islet cells may yield robust islet cells for diabetes therapy. We establish a method of electrofusion between dispersed islet cells and MSCs in rats. The fusion cells maintained glucose-responsive insulin release for 20 days in vitro. Renal subcapsular transplantation of fusion cells prepared from suboptimal islet mass (1,000 islets) that did not correct hyperglycemia even if co-transplanted with MSCs, caused slow but consistent lowering of blood glucose with significant weight gain within the observation period in streptozotocin-induced diabetic rats. In the fusion cells between rat islet cells and mouse MSCs, RT-PCR showed new expression of both rat MSC-related genes and mouse β-cell-related genes, indicating bidirectional reprogramming of both β-cell and MSCs nuclei. Moreover, decreased caspase3 expression and new expression of Ki-67 in the islet cell nuclei suggested alleviated apoptosis and gain of proliferative capability, respectively. These results show that electrofusion between MSCs and islet cells yield special cells with β-cell function and robustness of MSCs and seems feasible for novel therapeutic strategy for diabetes mellitus.

Subcutaneous transplantation of macroencapsulated porcine PEC normalized hyperglycemia in diabetic mice. Our results identified a potential for a favorable development of subcutaneous transplantation of porcine PEC as a cure for diabetes.

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.

Renal failure occurring in dogs during experimental acute pancreatitis and the effect on renal function of intravenous injections of ascitic fluid which accumulated during the acute pancreatitis were studied. Five hours after the induction of acute pancreatitis, the accumulation of 200 to 400 ml of ascitic fluid, and an elevation in hematocrit as well as a decreased mean arterial pressure were observed, which suggested hypovolemia due to plasma loss. At the same time, the renal blood flow, glomerular filtration rate, and urinary output decreased significantly. Hypovolemia was observed to be the main cause of renal failure in accordance with previous reports. When the sterile ascitic fluid was injected into healthy dogs, temporary hypotension was observed without changes in the hematocrit. However, the renal blood flow, glomerular filtration rate and urinary output decreased, together with an elevation in renal vascular resistance, even after the hypotension had returned to normal. This study shows that renal failure associated with acute pancreatitis occurred mainly as a direct result of hypovolemia but also that the sterile ascitic fluid contained nephrotoxic substances which were suspected to be unrelated to vasoactive substances or protease. Their removal is therefore necessary for the treatment and prevention of renal failure complicating acute pancreatitis.