Absence Of Islets Research Articles

Multivisceral Transplantation in Martinez-Frias Syndrome

Aim: Martinez-Frías Syndrome (MFS) is a very rare condition with autosomal recessive inheritance, firstly described in 1992. The most frequent patterns are hypoplastic pancreas, intestinal atresia and gallbladder aplasia/hipoplasia, probably due to a midline disorder affecting the development of the duodenal-biliary-pancreatic junction. Esophageal atresia and/or neonatal diabetes can be associated. There are few cases described in the literature, all with poor prognosis, mainly due to the progression of the liver disease. We present one girl with this condition who was succesfully transplanted. Case report: Female neonatal infant weighing 2200 g, 35 weeks of gestational age, with intrauterine growth retardation, and Spanish consanguineous gypsy parents. Physical examination did not show external abnormalities. A laparotomy due to intestinal obstruction was necessary within the first 24 hours of life, revealing duodenal atresia, intestinal malrotation type I, and gallbladder agenesia. Although surgery was uneventful, she developed refractory diabetes and pancreatic exocrine insufficiency, requiring parenteral nutrition for months with growth delay and multiple sepsis due to central line infections (12 episodes). The genetic study showed a mutation on 16q22.1 involving the gene RFX6. She was listed for multivisceral transplant, and was transplanted at 15 months of age, with no major postoperative complications. Her native spleen was preserved, and colon was included in the graft. The enterectomy revealed a patched substitution of the intestinal mucosa by gastric mucosa, and pancreatic hypoplasia with absence of islets and few neuroendocrine cells. Induction protocol consisted of Basiliximab, Tacrolimus with steroids were given for maintenance. Due to renal insufficiency and hypertension, conversion to Sirolimus was decided one year after transplantation, first combined with Tacrolimus, and later as monotherapy. After more than 5 years since transplant, the patient has not suffered any rejection, GVHD or PTLD episode. She is 6 yo, off parenteral nutrition, has a normal diet, with one bowel movement/day, with no malabsorption, just mild iron deficiency and enjoys a normal life. Conclusion: This is the longest survivor with MFS described in the literature. Multivisceral transplantation seems to be an available option for these children although future will determine if the disease is totally cured.FigureFigure

Toward a Bioartificial Pancreas: Diffusion of Insulin and IgG Across Immunoprotective Membranes with Controlled Hydrophilic Channel Diameters

Research continued toward a bioartificial pancreas (BAP). Our BAPs consist of a perforated nitinol scaffold coated with reinforced amphiphilic conetwork membranes and contain live pancreatic islets. The membranes are assemblages of cocontinuous hydrophobic domains and hydrophilic channels whose diameters were varied by the MW of hydrophilic segments between crosslinks (M(c,HI) = 32, 44, and 74 kg x mol(-1)). We studied the diffusion rate of insulin, BSA, and IgG across the membrane of the BAP in the absence of islets. Membranes of M(c,HI) = 74 kg x mol(-1) showed rapid insulin and BSA transport and negligible IgG diffusion. BAPs containing approximately 300 mouse islets showed appropriate response upon glucose challenge in vitro. The BAP implanted into diabetic mice reduced hyperglycemia and maintained islet viability for at least 4 d.

Encapsulation of Islets in Rough Surface, Hydroxymethylated Polysulfone Capillaries Stimulates VEGF Release and Promotes Vascularization after Transplantation.

The transplantation of encapsulated islets of Langerhans is one approach to treat type 1 diabetes without the need of lifelong immunosuppression. Capillaries have been used for macroencapsulation because they have a favorable surface-to-volume ratio and because they can be refilled. It is unclear at present whether the outer surface of such capillaries should be smooth to prevent, or rough to promote, cell adhesions. In this study we tested a new capillary made of modified polysulfone (MWCO: 50 kDa) with a rough, open-porous outer surface for islet transplantation. Compared with free-floating islets, encapsulation of freshly isolated rat islets affected neither the kinetics nor the efficiency of glucose-induced insulin release in perifusion experiments. Free-floating islets maintained insulin secretion during cell culture but encapsulated islets gradually lost their glucose responsiveness and released VEGF. This indicated hypoxia in the capillary lumen. Transplantation of encapsulated rat islets into diabetic rats significantly reduced blood glucose concentrations from the first week of implantation. This hypoglycaemic effect persisted until explantation 4 weeks later. Transplantation of encapsulated porcine islets into diabetic rats reduced blood glucose concentrations depending on the islet purity. With semipurified islets a transient reduction of blood glucose concentrations was observed (2, 8, 18, 18 days) whereas with highly purified islets a sustained normoglycaemia was achieved (more than 28 days). Explanted capillaries containing rat islets were covered with blood vessels. Vascularization was also observed on capillaries containing porcine islets that were explanted from normoglycaemic rats. In contrast, on capillaries containing porcine islets that were explanted from hyperglycemic rats a fibrous capsule and lymphocyte accumulations were observed. No vascularization on the surface of transplanted capillaries was observed in the absence of islets. In conclusion, encapsulated islets can release VEGF, which appears to be an important signal for the vascularization of the capillary material. The rough, open-porous outer surface of the polysulfone capillary provides a site well suited for vascular tissue formation and may allow a prolonged islet function after transplantation.

Detection by ESR of DMPO hydroxyl adduct formation from islets of langerhans

Electron spin resonance (ESR) spectroscopy together with spin trapping techniques and the application of state-of-the-art loop gap resonators was used to provide a direct measure of spontaneous oxygen radical production by homogenates of freshly isolated and cultured rat pancreatic islets. Using the spin trap agent, 5,5-dimethyl-l-pyrroline-N-oxide (DMPO), we were able to detect production by islets of an ESR-sensitive radical signal consisting of a quartet with intensity ratio of 1:2:2:1 and hyperfine splitting of a N = a H = 14.9 Gauss, which is consistent with the DMPO-OH adduct. The amplitude of the signal was decreased by decreasing amount of islets and not detected in the absence of islets. Formation of the DMPO-OH adduct was diminished by the hydroxyl radical scavengers (e.g., ethanol, dimethylsulfoxide, and dimethylthiourea). Only partial attenuation of signal was produced by incubation with an iron chelator or using chelex-treated buffers. The ESR signal was insensitive to the xanthine oxidase inhibitor, oxypurinol, or to superoxide dismutase, but was eliminated in a concentration-dependent manner by either potassium cyanide or catalase (but not heat-inactivated catalase). These observations suggest that the origin of the DMPO-OH arose not from free hydroxyl radicals but primarily from endogenous hydrogen peroxide production perhaps of mitochondrial origin. The development of this technology has implications for the potential measure of oxygen radical production in islet homogenates under pathologic conditions as well as to the application of other cell culture systems.

Congenital Diabetes Mellitus and Fatal Secretory Diarrhea in Two Infants

Two unrelated male infants presented with brittle insulin-dependent diabetes mellitus in the first days of life. Subsequently they each developed severe secretory diarrhea, with stool volumes of more than 100 ml/kg/day. Extensive biochemical and serological investigation failed to reveal the etiology of the diarrhea. The infants, cared for at different institutions, underwent therapeutic trials of various agents including loperamide, cholestyramine, prednisone, indomethacin, and somatostatin analogue, without response. Both infants succumbed to septicemia and malnutrition related to diarrhea and poor control of glycemia. At autopsy, both were found to have absence of islets of Langerhans in the pancreas, and diffuse dysplastic changes in small and large intestinal mucosae. In particular, the entire alimentary tract in each case was lined by epithelia most typical of foregut mucosa: secretory-type glands, absent crypts of Lieberkuhn, and absent villi. These cases are contrasted with previously-reported infants with congenital diabetes mellitus, and the possible interrelation of these two highly unusual findings, congenital diabetes mellitus and diffuse intestinal dysplasia, is examined.