Impact of Prevascularization on Immunological Environment and Early Engraftment in Subcutaneous Islet Transplantation.

BACKGROUND: The utilization of islet-like cells derived from pluripotent stem cells may resolve the scarcity of islet transplantation donors. The subcutaneous space is a promising transplantation site because of its capacity for graft observation and removal, thereby ensuring safety. To guarantee subcutaneous islet transplantation, physicians should ensure ample blood supply. Numerous methodologies, including prevascularization, have been investigated to augment blood flow, but the optimal approach remains undetermined. METHODS: From C57BL/6 mice, 500 syngeneic islets were transplanted into the prevascularized subcutaneous site of recipient mice by implanting agarose rods with basic fibroblast growth factor at 1 and 2 wk. Before transplantation, the blood glucose levels, cell infiltration, and cytokine levels at the transplant site were evaluated. Furthermore, we examined the impact of the extracellular matrix capsule on graft function and the inflammatory response. RESULTS: Compared with the 1-wk group, the 2-wk group exhibited improved glycemic control, indicating that longer prevascularization enhanced transplant success. Flow cytometry analysis detected immune cells, such as neutrophils and macrophages, in the extracellular matrix capsules, whereas cytometric bead array analysis indicated the release of inflammatory and proinflammatory cytokines. Treatment with antitumor necrosis factor and anti-interleukin-6R antibodies in the 1-wk group improved graft survival, similar to the 2-wk group. CONCLUSIONS: In early prevascularization before subcutaneous transplantation, neutrophil and macrophage accumulation prevented early engraftment owing to inflammatory cytokine production.

Antipsychotic olanzapine-induced misfolding of proinsulin in the endoplasmic reticulum accounts for atypical development of diabetes.

Second-generation antipsychotics are widely used to medicate patients with schizophrenia, but may cause metabolic side effects such as diabetes, which has been considered to result from obesity-associated insulin resistance. Olanzapine is particularly well known for this effect. However, clinical studies have suggested that olanzapine-induced hyperglycemia in certain patients cannot be explained by such a generalized mechanism. Here, we focused on the effects of olanzapine on insulin biosynthesis and secretion by mouse insulinoma MIN6 cells. Olanzapine reduced maturation of proinsulin, and thereby inhibited secretion of insulin; and specifically shifted the primary localization of proinsulin from insulin granules to the endoplasmic reticulum. This was due to olanzapine's impairment of proper disulfide bond formation in proinsulin, although direct targets of olanzapine remain undetermined. Olanzapine-induced proinsulin misfolding and subsequent decrease also occurred at the mouse level. This mechanism of olanzapine-induced ß-cell dysfunction should be considered, together with weight gain, when patients are administered olanzapine.

The MEK Inhibitor Trametinib Suppresses Major Histocompatibility Antigen-mismatched Rejection Following Pancreatic Islet Transplantation.

BACKGROUND: Potential adverse effects, such as functional impairment of islets, render conventional immunosuppressive drugs unsuitable for use in islet transplantation. In addition, as a single therapy, they cannot prolong islet allograft survival. Here, we investigated the utility of the mitogen-activated protein kinase inhibitor trametinib and asked whether it ameliorates acute rejection of transplanted islets without the need for conventional immunosuppressants. METHODS: Islets from fully major histocompatibility complex-mismatched BALB/c mice were transplanted into streptozotocin-induced diabetic C57BL/6 mice via the portal vein. These mice received trametinib or vehicle (orally) for 28 days. Isolated islets from BALB/c mice were incubated in vitro with different concentrations of trametinib to determine viability and function. RESULTS: Trametinib (0.1 and 0.3 mg/kg) prolonged graft survival significantly (P = 0.0007 and P = 0.005, respectively) when compared with vehicle. Histologic analyses revealed that cellular infiltration of the graft by lymphocytes was inhibited significantly on day 7 (P < 0.05). In addition, trametinib suppressed functional differentiation of naive CD4+ T cells in recipients. Expression of mRNA encoding inflammatory cytokines interleukin (IL)-2, tumor necrosis factor α, and interferon γ in recipients treated with trametinib was also inhibited (P < 0.001, P < 0.05, and P < 0.01, respectively). Trametinib also increased production of IL-4 and IL-10 (P < 0.05 and P = 0.20, respectively). In vitro, islets incubated with different concentrations of trametinib exhibited no harmful effects with respect to viability and function. CONCLUSIONS: Trametinib delayed islet graft rejection by inhibiting functional differentiation of naive CD4+ T cells and regulating inflammatory cytokines. Trametinib might be a promising candidate for maintenance immunosuppressive therapy after allogeneic islet transplantation.

Mitomycin C treatment improves pancreatic islet graft longevity in intraportal islet transplantation by suppressing proinflammatory response.

The in vitro culture period prior to cell transplantation (i.e. pancreatic islet transplantation) enables cell modification and is thus advantageous. However, the islet preconditioning method has not been fully explored. Here we present a simple approach for islet preconditioning that uses the antibiotic mitomycin C (MMC), which has antitumor activity, to reduce islet immunogenicity and prevent proinflammatory events in an intraportal islet transplantation model. Freshly isolated mice islets were treated for 30 min with 10 µg/mL MMC or not, cultured for 20 h and transplanted into the livers of syngeneic or allogeneic diabetic mouse recipients. In the allogeneic model, MMC preconditioning significantly prolonged graft survival without requiring immunosuppressants. In vitro, MMC treatment suppressed the expression of proinflammatory cytokines in islet allografts, while immunohistochemical studies revealed the suppression of inflammatory cell infiltration into MMC-treated allografts relative to untreated allografts. Furthermore, MMC preconditioning significantly suppressed the mRNA expression of proinflammatory cytokines into the transplant site and induced the differentiation of regulatory T cells with the ability to suppress CD4+ T cell-mediated immune responses. In conclusion, islet preconditioning with MMC prolonged graft survival in an intraportal islet transplantation model by suppressing proinflammatory events and inducing potentially regulatory lymphocytes.

Proposal for a Safe and Functional Pancreaticojejunostomy Technique from a Histopathological Perspective.

BACKGROUND: To prevent leakage of pancreatic juice from the main pancreatic duct (MPD), complete external drainage appears to be the most effective technique. However, because this requires a pancreatic stent tube to be ligated with MPD, duct-to-mucosa pancreaticojejunostomy (PJ) is difficult. From our histopathological examination, a large amount of pancreatic juice is drained from the ducts other than MPD. This study aimed to evaluate our new conceptual technique of PJ after pancreaticoduodenectomy (PD). METHODS: We considered it important to drain pancreatic juice from the branch pancreatic ducts to the intestinal tract and to perform duct-to-mucosa PJ, while pancreatic juice from MPD is completely drained out of the body. We designed a technique that could simultaneously achieve these points. In our technique, which is based on conventional "two-row" anastomosis, a stent tube is fixed with MPD and its surrounding tissue by purse-string suture at the cut surface of the pancreas, and duct-to-mucosa PJ is concomitantly performed. RESULTS: Of 45 patients undergoing PD, 12 of soft pancreas underwent surgery with this technique. According to the classification of the International Study Group on Pancreatic Fistula, a Grade A PF was observed in four patients, whereas no patient had a Grade B or C PF. CONCLUSIONS: We propose our anastomotic technique that could simultaneously prevent PF and keep the pancreatic duct patent.

The Cavitron ultrasonic surgical aspirator with a low amplitude is a useful dissection device for surgical procedures: application to vascular detachment and lymph node dissection.

In surgical procedures, although resection and hemostasis maneuvers have become more efficient through the use of dedicated devices, no dedicated device for the dissecting (detaching) maneuver exists at present. The Cavitron ultrasonic surgical aspirator (CUSA: Integra lifesciences Corporation, NJ, USA) is a device originally used mainly for hepatic parenchyma resection in the gastrointestinal surgical field. Tissue is selectively fragmented by an ultrasonically vibrating chip at the tip of the device. Furthermore, physiologic saline is ejected from the tip and aspirated with the fragmented tissue by the device. By reducing the amplitude of the CUSA to 10-20 %, we have been using the device not only for hepatic parenchyma resection but also for dissection in gastrointestinal surgical procedures in general. Here, we explain the details of the techniques that we routinely use, such as dissection of vessels and lymph nodes in radical operations for gastrointestinal cancer. With the CUSA set at a greatly reduced amplitude, dissection can be performed in consideration of layers, surfaces, and membranes while tissue damage and bleeding are minimized. The device is useful for performing higher quality operations.

Pathogenic mechanisms of intestinal pneumatosis and portal venous gas: should patients with these conditions be operated immediately?

We aimed to histologically observe portal venous gas (PVG)-causing intestinal pneumatosis (IP) and evaluate pathogenic mechanisms and therapeutic strategies, including decisions on whether emergency surgery should be performed. Autopsy was performed in two cases of nonocclusive mesenteric ischemia (NOMI). We directly histologically observed the pathogenic mechanisms of IP caused by gas-producing bacteria and IP considered to be caused by mechanical damage to the intestinal mucosa. IP can be classified hypothetically into the following types according to pathogenesis: (1) infection, (2) rupture (damage) of the intestinal mucosa + increased intestinal intraluminal pressure, and (3) mixed type. In cases of IP caused by gas-producing bacteria or IP associated with intestinal wall damage extending beyond the mucosa to the deep muscular layer, emergency surgery should be considered. However, it is highly possible that patients who test negative for infection with gas-producing bacteria whose intestinal wall damage remains only in the mucosa can be conservatively treated.