No abstract

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.

In a prospective trial to determine whether gastric surgery induces gallbladder sludge and stone formation, 48 patients with gastric cancer were ultrasonographically examined with simultaneous observation on changes in gallbladder contractile function before and serially for 5 years after gastrectomy. Gallbladder sludge formation was induced with a high frequency of 42% 1 month after gastrectomy, with corresponding significant lowering of gallbladder contractile function. Most of gallbladder sludges, however, disappeared within 12 months in relation to the gradual recovery of gallbladder contractile function. Conversely, gallstone developed in nine patients (18.8%), mostly more than 6 months after gastrectomy. Interestingly, gallstone formation was induced in seven patients who were sludge negative. An evolvement of gallbladder sludge into stone was observed in only two patients, who were, however, treated with intravenous hyperalimentation. This study first provides evidence for the relationship between gastrectomy and a considerably high frequency of incidence of gallbladder sludge and stone in relation to changes in gallbladder kinetics after gastrectomy.

Islet isolation involves enzymatic digestion of the interstitial matrix and mechanical disruption of the tissue. It is possible that a fundamental change of islet biology resulting from the loss of critical factors required for islet function or survival will occur. Extracellular matrix (ECM) is one of the most important components of the islet microenvironment. Reconstruction of the cell-matrix relationship seems to be effective for improving the loss of differentiated islet structure and function. The purpose of this study was to characterize and compare the effects of collagen gel mixture or Matrigel on β-cell function and islet cell survival. After isolation by the collagenase digestion technique, rat islets were divided and cultured with various types of collagen gel mixture. They were assessed for their glucose-stimulated insulin secretion and cell viability. Glucose-induced insulin secretion of islets cultured with collagen type I gel or a mixture of collagen type I and IV was improved after 11 days in culture. In conclusion, a type of gel composed of collagen type I and/ or type IV as an islet microenvironment is sufficient to maintain glucose responsiveness and may be useful for islet transplantation.

This study provides evidence that the subcutaneous tissue is a promising site for pancreatic islet transplantation, which suggests the acceptability of this treatment for diabetic recipients.