Shoichiro Sumi

Gallbladder sludge and stone formation in relation to contractile function after gastrectomy. A prospective study.

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.

Effect of synthetic neuromedin U-8 and U-25, novel peptides identified in porcine spinal cord, on splanchnic circulation in dogs.

Two novel peptides which exert a potent stimulant effect on rat uterus smooth muscle have recently been identified in porcine spinal cord. These peptides designated neuromedin U-8 and U-25 have been reported to exert a hypertensive effect in rats. But further biological activities are not known. In the present study, the effect of these peptides on blood flow in portal vein, superior mesenteric artery and pancreatic tissue and on blood pressure were examined in dogs, utilizing recently developed ultrasonic transit time volume flow meter and laser Doppler flow meter. Neuromedin Us potently reduced blood flow in superior mesenteric artery. The minimum reductions could be observed even at very small doses of neuromedin U-25 (32 fmol/kg) and U-8 (90 fmol/kg), while the maximal reductions of 48.4 and 51.0% were attained at the doses of 320 pmol/kg (U-25) and 900 pmol/kg (U-8), respectively. These peptides also reduced portal vein blood flow, and the maximal reductions of 42.1 and 37.2% were attained at the doses of 32 pmol/kg (U-25) and 90 pmol/kg (U-8), respectively. On the other hand, blood flow in pancreatic tissue increased slightly with the maximal increases of 13.8% at 3.2 pmol/kg (U-25) and 11.8% at 9 pmol/kg (U-8), respectively. The maximal increases of blood pressure were 5.2% at 320 pmol/kg (U-25) and 4.3% at 90 pmol/kg (U-8). Furthermore, neither neuromedin U-25 nor U-8 influenced the axillary artery blood flow, suggesting their selective effect on splanchnic blood flow. Because of the potent and probably selective activity on splanchnic circulation, neuromedin U-25 and U-8 may well be recognized as physiologically significant novel neuropeptides or hormones.

In vivo functioning and transplantable mature pancreatic islet-like cell clusters differentiated from embryonic stem cells.

Introduction Although the differentiation of embryonic stem (ES) cells to islet like clusters using differentiation method without employing gene transfer technique has been recently reported, neither endocrine granules in the cytoplasm nor in vivo function of differentiated islet like clusters has been demonstrated. Aims To investigate whether ES cells could be differentiated to mature islet like clusters which show in vivo function after transplantation as well as retain endocrine granules in the cytoplasm by electron microscopic observation. Methodology In this experiment, using mouse embryonic stem (mES) cells as a model system for lineage specific differentiation, we tried to differentiate mES cells to pancreatic islet-like cell clusters (PICCs) through a series of treatments (4-step procedure). Differentiated PICCs were analyzed and characterized by various techniques, such as RT-PCR, immunohistochemistry, electron microscopic observation, in vitro static incubation test, and in vivo transplantation to diabetic animals. Results Differentiated islet-like cell clusters from ES cells using our newly developed method (four-step procedure) showed strong expression of essential specific genes to the endocrine pancreas and also specific genes to the exocrine pancreas demonstrating that these islet-like clusters were mature from the developmental biologic point of view. These differentiated cells clearly revealed many mature insulin secretory granules of pleomorphic shape in the cytoplasm as well as well-developed rough endoplasmic reticulum. In vitro study indicated that differentiated cells retain a potent insulin secretory responsiveness to glucose stimulation. Furthermore, the islet-like cell clusters significantly decreased high blood glucose levels almost to normal levels when grafted to streptozotocin-induced diabetic mice without induction of any teratoma formation after transplantation. Conclusion Our results provide evidence that ES cells could differentiate to functioning and transplantable mature pancreatic islet-like cell clusters using our newly developed differentiation method without employing gene transfer technique. This study may lead to a basis for production of indefinite sources of islets that could be applicable for future clinical trial.

Experimental hybrid islet transplantation: application of polyvinyl alcohol membrane for entrapment of islets.

In this study, we first examined in vitro a polyvinyl alcohol membrane to be used to contain hybrid islet cells, and second we tested a bioartificial pancreas with entrapment of pancreatic islets in polyvinyl alcohol membrane in rats with experimentally induced diabetes. The permeability of the polyvinyl alcohol membrane to different substances was studied in a two-cell chamber system. Glucose, insulin, and nutrients passed through the membrane easily, whereas the passage of immunoglobulin G was completely prevented, indicating that this membrane could be effective in protecting the bioartificial pancreas from immunorejection. Approximately 2,000 islets collected from three Sprague-Dawley rats were enclosed in a mesh-reinforced polyvinyl alcohol tube and transplanted into the peritoneal cavity of six Wistar rats with streptozotocin-induced diabetes. Their nonfasting serum glucose levels were significantly decreased for at least 12 days. Six diabetic rats receiving intra-peritoneal transplantation of free islets without the tube showed a slight but significant decrease in nonfasting serum glucose levels for only 3 days. One diabetic rat with transplantation of the bioartificial pancreas had a significant and sustained decrease in nonfasting glucose levels from pretransplanted levels of 440–500 mg/dl to a mean value of 162 ± 13 mg/dl for over 3 months without immunosuppression. The bioartificial pancreas was then removed, and glucose levels gradually increased to over 500 mg/dl. The results of the present study suggest that a bioartificial pancreas with entrapment of islets in a polyvinyl alcohol membrane could be a promising therapeutic approach to diabetes mellitus.

Encapsulated islets transplantation: Past, present and future.

Islet transplantation could become an ideal treatment for severe diabetes to prevent hypoglycemia shock and irreversible diabetic complications, once some of the major and unresolved obstacles are overcome, including limited donor supplies and side effects caused by permanent immunosuppressant use. Approximately 30 years ago, some groups succeeded in improving the blood glucose of diabetic animals by transplanting encapsulated islets with semi-permeable membranes consisting of polymer. A semi-permeable membrane protects both the inner islets from mechanical stress and the recipients immune system (both cellular and humoral immunities), while allowing bidirectional diffusion of nutrients, oxygen, glucose, hormones and wastes, i.e., immune-isolation. This device, which enables immune-isolation, is called encapsulated islets or bio-artificial pancreas. Encapsulation with a semi-permeable membrane can provide some advantages: (1) this device protects transplanted cells from the recipients immunity even if the xenogeneic islets (from large animals such as pig) or insulin-producing cells are derived from cells that have the potential for differentiation (some kinds of stem cells). In other words, the encapsulation technique can resolve the problem of limited donor supplies; and (2) encapsulation can reduce or prevent chronic administration of immunosuppressants and, therefore, important side effects otherwise induced by immunosuppressants. And now, many novel encapsulated islet systems have been developed and are being prepared for testing in a clinical setting.

Subcutaneous transplantation of macroencapsulated porcine pancreatic endocrine cells normalizes hyperglycemia in diabetic mice.

Background. The ultimate goal of islet transplantation is the unlimited availability of insulin-secreting cells to be transplanted in a simple procedure that requires no use of immunosuppressive drugs. Immunoisolation of xenogeneic pig islets for transplantation has great potential therapeutic benefits for treatment of diabetes. Methods. Approximately 4×106 porcine pancreatic endocrine cells (PEC) isolated from 6-month-old pigs were macroencapsulated in agarose-poly(styrene sulfonic acid) mixed gel and implanted into a prevascularized subcutaneous site in streptozotocin-induced C57BL/6 diabetic mice. Animals receiving an equal number of free porcine PEC were used as controls. After transplantation, nonfasting blood glucose, body weight, intraperitoneal glucose tolerance test, and immunohistologic evaluations were processed. Results. All 10 animals receiving the subcutaneous xenografts of the macroencapsulated porcine PEC normalized hyperglycemia within 5 days after transplantation, maintained the duration of normoglycemia for 24 to 76 days, and gradually gained weight. The subcutaneous xenografts of free porcine PEC could not reverse hyperglycemia. The recipient became hyperglycemic again when the implanted graft was retrieved at day 45 after transplantation. The glucose clearances were significantly ameliorated at day 21 and day 45 after transplantation when compared with those in diabetic mice. The immunohistochemical results revealed an inherent intact structure of the macroencapsulated porcine PEC and positive double-immunofluorescence staining for insulin and glucagon. Conclusions. 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.

Chitosan/gelatin hydrogel as immunoisolative matrix for injectable bioartificial pancreas

Abstract:  Background:  The feasibility of using chitosan/gelatin hydrogel as immunoisolative matrix to provide an additional protection to the microencapsulated islet cells was demonstrated in this study. We hope that the use of hydrogel can extend the functional longevity of microencapsulated islet cells during xenotransplantation.

PHLDA3 is a novel tumor suppressor of pancreatic neuroendocrine tumors.

Significance Pancreatic neuroendocrine tumors (PanNETs) are a rare pathology, and molecular mechanisms underlying their development have not been well defined. This article shows that a two-hit inactivation of the PHLDA3 gene is required for PanNET development: methylation of the locus and loss of heterozygosity. PHLDA3 functions as a suppressor of PanNETs via repression of Akt activity and downstream Akt-regulated biological processes. In addition, the tumor-suppressing pathway mediated by MEN1, a well known suppressor of PanNETs, is dependent on the pathway mediated by PHLDA3, and inactivation of PHLDA3 and MEN1 cooperatively contribute to PanNET development. A novel PHLDA3-mediated pathway of tumor suppression that is important in the development of PanNETs is demonstrated, and the findings may contribute to personalized medicine of PanNET patients. The molecular mechanisms underlying the development of pancreatic neuroendocrine tumors (PanNETs) have not been well defined. We report here that the genomic region of the PHLDA3 gene undergoes loss of heterozygosity (LOH) at a remarkably high frequency in human PanNETs, and this genetic change is correlated with disease progression and poor prognosis. We also show that the PHLDA3 locus undergoes methylation in addition to LOH, suggesting that a two-hit inactivation of the PHLDA3 gene is required for PanNET development. We demonstrate that PHLDA3 represses Akt activity and Akt-regulated biological processes in pancreatic endocrine tissues, and that PHLDA3-deficient mice develop islet hyperplasia. In addition, we show that the tumor-suppressing pathway mediated by MEN1, a well-known tumor suppressor of PanNETs, is dependent on the pathway mediated by PHLDA3, and inactivation of PHLDA3 and MEN1 cooperatively contribute to PanNET development. Collectively, these results indicate the existence of a novel PHLDA3-mediated pathway of tumor suppression that is important in the development of PanNETs.

Improvement of focal ischemia-induced rat dopaminergic dysfunction by striatal transplantation of mouse embryonic stem cells.

Middle cerebral artery occlusion (MCAO) caused behavioral dysfunction with massive neuronal loss. Cell transplantation may recover this deficit by replacing damaged brain cells. In this study, we examined the effects of transplantation of mouse embryonic stem (ES) cells or ES cell-derived neuron-like (ES-N) cells on behavioral function in ischemic rats. Seven days after MCAO, ES or ES-N cells were transplanted into ipsilateral striata (but not the substantia nigra) of ischemic rats. Transplanted rats exhibited a gradual reduction in the number of rotations induced by methamphetamine compared to vehicle-injected rats. These rats also showed a significant improvement in rota-rod performance. At 15 weeks after transplantation, immunoreactivities for tyrosine hydroxylase (TH) and dopamine transporter (DAT) in the striatum were significantly recovered in rats grafted with ES or ES-N cells compared to vehicle-injected rats. These results suggest that intrastriatal-transplantation of ES or ES-N cells improved the dopaminergic function and subsequently recover behavioral dysfunction in focal ischemic rats.

Effects of Synthetic Human Gastric Inhibitory Polypeptide on Splanchnic Circulation in Dogs

Changes in blood flow in the celiac artery, superior mesenteric artery, and pancreas in response to an intravenous injection of synthetic human gastric inhibitory polypeptide (GIP) were determined simultaneously and continuously in anesthetized dogs, using a transit-time ultrasonic flowmeter and a laser-Doppler flowmeter. Injection of GIP significantly increased superior mesenteric arterial flow in a dose-related manner (by 9%, 43%, and 139% at 30 s after an injection at the doses of 3, 50, and 800 pmol/kg, respectively). In contrast, celiac arterial flow was not significantly altered by GIP at any of the three doses. Calculated vascular resistance in the superior mesenteric artery decreased after GIP infusion, whereas that in the celiac artery was not changed by GIP. Pancreatic blood flow decreased significantly after GIP injection at the doses of 50 and 800 pmol/kg (by 11% and 17%, respectively). Our data indicate that there is a substantial difference in the hemodynamic responses to GIP among splanchnic organs, and suggest that GIP acts specifically on the mesenteric vasculature.