Islet graft survival inside macroencapsulation devices is suboptimal. We hypothesized that induction of neovascularization by preimplantation of devices would improve the physiological conditions, thereby lowering the number of islets required for cure. Several rat islets were transplanted to TheraCyte immunoprotective devices implanted subcutaneously in diabetic athymic mice. Cure rates in the groups with preimplanted devices were significantly better than in those with freshly implanted devices (375 islets: 8/8 vs. 1/6, P=0.003; 125 islets: 6/6 vs. 0/7, P=0.001). Morphometric evaluations of the 125 islet groups showed higher fractional and absolute volumes of endocrine tissue in the group with preimplanted devices (P<0.001 and P=0.035, respectively). In the following dose titration study, using preimplanted devices, as low as 50 islets cured diabetic mice (100% cure, n=6). We conclude that preimplantation significantly lowers the curative dose of macroencapsulated islets to levels resembling those of free islets transplanted under the renal capsule.
Aims/hypothesis: Early islet graft survival is crucial in determining the outcome after clinical islet transplantation. Exendin-4 has anti-apoptotic and beta cell proliferative properties, which could improve islet graft survival and function. The aim of these studies was to evaluate the effect of exendin-4 on graft function after islet transplantation. Materials and methods: Rat islets were transplanted under the kidney capsule of diabetic athymic mice. First, we performed a dose-finding study and found that 30 islets just failed to cure diabetic mice. In the following two studies, we transplanted 30 islets and treated the mice that had received these islets with exendin-4 i.p. (100 ng/mouse) once daily for 1 week. Blood glucose levels and body weights were used as evaluation criteria. In the short-term study evaluation was done at day 8. This study was followed by a long-term study that was evaluated at 4 weeks. In this study, islets were precultured with exendin-4 (0.1 nmol/l) in addition to the treatment given to mouse-recipients of transplanted islets. The cured mice underwent an intraperitoneal glucose tolerance test (IPGTT). Results: In the shortterm study, 63% of exendin-4-treated mice achieved graft function compared with 21% of untreated mice (p=0.033). In the long-term study, 88% of treated mice had functioning grafts compared with 22% of controls (p=0.015). Cured mice showed a normal response in the IPGTT, comparable to that of healthy mice. Exendin-4-treated mice gained significantly more weight than their untreated counterparts. Conclusions/interpretation: Islet preculture and a short course of therapy with exendin-4 improves metabolic control after rat islet transplantation in athymic mice. The beneficial effect lasts beyond the treatment period.
Background: Parastomal hernia (PSH) after urinary diversion with ileal conduit is frequently a clinical problem. Objective: To investigate whether a prophylactic lightweight mesh in the sublay position can reduce the cumulative incidence of PSH after open cystectomy with ileal conduit. Design, setting, and participants: From 2012 to 2017, we randomised 242 patients 1:1 to conventional stoma construction (n = 124) or prophylactic mesh (n = 118) at three Swedish hospitals (ISRCTN 95093825). Outcome measurements and statistical analysis: The primary endpoint was clinical PSH, and secondary endpoints were radiological PSH assessed in prone position with the stoma in the centre of a ring, parastomal bulging, and complications from the mesh. Results and limitations: Within 24 mo, 20/89 (23%) patients in the control arm and 10/ 92 (11%) in the intervention arm had developed a clinical PSH (p = 0.06) after a median follow-up of 3 yr, corresponding to a hazard ratio of 0.45 (confidence interval 0.24-0.86, p = 0.02) in the intervention arm. The proportions of radiological PSHs within 24 mo were 22/89 (25%) and 17/92 (19%) in the two study arms. During follow-up, five patients in the control arm and two in the intervention arm were operated for PSH. The median operating time was 50 min longer in patients receiving a mesh. No differences were noted in proportions of Clavien-Dindo complications at 90 d postoperatively or in complications related to the mesh during follow-up. Conclusions: Prophylactic implantation of a lightweight mesh in the sublay position decreases the risk of PSH when constructing an ileal conduit without increasing the risk of complications related to the mesh. The median surgical time is prolonged by mesh implantation. Patient summary: In this randomised report, we looked at the risk of parastomal hernia after cystectomy and urinary diversion with ileal conduit with or without the use of a prophylactic mesh. We conclude that such a prophylactic measure decreased the occurrence of parastomal hernias, with only a slight increase in operating time and no added risk of complications related to the mesh.
In this study, we evaluated the effects of exendin-4 on free and encapsulated islet grafts in a rodent model. We also investigated the role of a transcription factor, hypoxia-inducible factor-1 (HIF-1), in mediating the beneficial effects of exendin-4. Diabetic athymic mice were transplanted with free rat islets under the kidney capsule or with macroencapsulated rat islets SC with or without exendin-4, islet preculture (exendin-4 0.1 nM for 20 h), and/or recipient treatment (IP 100 ng/day, day 0-7). The mice were followed for 4 weeks and the graft function and β-cell volume were evaluated. The effects of exendin-4 on islet HIF-1α mRNA and protein expression and on ATP content in a rat insulinoma cell line (INS-1E) were also examined. Preculture with exendin-4 followed by recipient treatment improved the outcome of both free (73% graft function vs. 26% in controls, p = 0.03) and macroencapsulated islet grafts (100% vs. 25% in controls, p = 0.02). In macroencapsulated grafts, the exendin-4-treated group had significantly larger endocrine volume, less graft necrosis, and more blood vessels around the capsule. In rat islets cultured with exendin-4, HIF-1α mRNA and protein expression were significantly enhanced. ATP content was increased in exendin-4-treated INS-1E cells under hypoxic conditions. The improved functional outcome after transplantation of a marginal islet mass with a brief initial treatment with exendin-4 is related to a larger surviving endocrine cell volume. Exendin-4 may improve islet graft resistance to hypoxia during the peritransplant period by increasing the expression of HIF-1α.
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