Functional improvement of pig islet with exocrine encapsulation

Porcine-specific obstacles in islet isolation frequently result from the low purity or contamination with exocrine tissues. We implemented a new technique involving as capsulation of islets with excess exocrine tissue as a beneficial material to address those difficulties. Pig islets were hand-picked as high purity (HI) or low purity (LO) islets containing significant amounts of exocrine tissue. We performed static (ST) or shaking (SK) cultures of HI and LO islets. Islet function was examined after 24 hours by a glucose challenge test. Insulin secretion into the culture media was continuously measured using ELISA during a 6-day culture period. Islet function after 24 hours exhibited better maintenance under SK than ST culture as assessed by a stimulation index. The ideal islet morphology was seen in LO islets at 3 days of SK culture with typical islet shapes of a smooth surface and a spherical configuration. In contrast, typical islet morphology was not observed in HI islets under SK culture; maintenance of typical spherical appearances was difficult. Insulin secretion from LO islets under SK culture was higher than under other conditions during the 6-day period. Under SK culture conditions, exocrine-encapsulated LO islets showed enhanced islet function by condensing loose islet aggregates into firm spheroids with native exocrine tissues as a natural scaffold.ope

Hybrid cellular spheroids from hepatocellular carcinoma and insulin-secreting cell lines

During islet transplantation into the portal vein of the liver, the islet cells are expected to have complex interactions with hepatocytes. However, the mechanism underlying this interaction is not yet understood. Hence, we developed cellular complexes containing a mixture of human hepatocellular carcinoma cell line (Hep-G2) and rat insulin-secreting cell line (RIN-5F) by using a co-culture model and studied the function and morphology of the resultant hybrid cellular spheroids (HCSs). The RIN-5F and Hep-G2 cells were suspension cultured and, within 5 days of culture, the two types of cells aggregated to yield spheroids. The functionality of the thus formed HCSs was evaluated by measuring the levels of insulin and albumin in the culture supernatant. The HCSs retained their insulin- and albumin-secreting ability and their morphology, as revealed by immunohistological staining. The insulin and albumin levels secreted by the HCSs were considerably higher than those secreted by spheroids of single-cell origin. Generally, obtaining complexes from more than two types of cells is difficult. However, we were able to generate HCSs. We believe that this culture method could have various applications such as studying the in vitro cell-cell interactions and developing new cell transplantation models.ope

Impact of coculture with ischemic preconditioned hepatocellular carcinoma cell line (Hep-G2) cells on insulin secreting function of rat insulin-secreting cell line (RIN-5F) cells

INTRODUCTION: Although Islet cell isolation and culture have been well developed, there has been little progress to prolong transplanted islet survival. Hepatic ischemia and insufficient neovascularization of islets are considered to be the barriers to long-term survival, Hepatocytes that survive ischemic injury have been reported to protect themeslves and regenerate using the IL-6 interleukin 6 and STAT3 pathways. MATERIALS AND METHODS: The hepatocellular carcinoma (Hep-G2) cell line preconditioned for 0, 2, 4, 6, and 24 hours in a hypoxic chamber, was cocultured with rat insulin-secreting celline (RIN-5F) cells. We measured cell viabilities, insulin secretion, and p-STAT3, IL-6, and NF-κB levels. RESULTS: Cocultured Hep-G2 and RIN-5F cells aggregated to form spheroids. Viabilities of Hep-G2 cells were no different after various ischemic preconditioning times, but insulin secretion increased in a time-dependent fashion with preconditioning. Western blotting showed p-STAT3, NF-κB, and IL-6 levels to increase with preconditioning time. CONCLUSION: The IL-6/STAT3 pathway of Hep-G2 cells after ischemic injury showed beneficial effects on insulin secretion of RIN-5f cells cocultured with themselves.ope

AEB-071 versus tacrolimus monotherapy to prevent acute cardiac allograft rejection in the rat: a preliminary report

Inhibition of T-cell activation is the most efficient way to prevent transplant rejection. Protein kinase C (PKC) is an important signaling enzyme in the activation and regulation of T lymphocytes. AEB-071 (AEB) is a low-molecular-weight compound that blocks early T-cell activation via selective inhibition of PKC, a mechanism that differs from that of the calcineurin inhibitors. The present study sought to compare the effects of AEB versus tacrolimus (Tac) to prevent acute rejection in rats that had undergone heterotopic heart transplantation. We investigated the Brown Norway-Lewis rat strain combination for cardiac graft survival over 30 days after transplantation using varying doses of oral AEB and Tac monotherapy. Grafts were monitored by daily palpation; cessation of palpable ventricular contraction was considered to be rejection. Apart from necropsy, we performed histologic examinations of cardiac graft at 7 days after transplantation. In untreated recipients, allograft mean survival times (MST) was 6.83+/-0.41 days. AEB at 15, 30, or 60 mg/kg versus Tac at 1.2 mg/kg significantly prolonged graft survival to a MST of 12.33+/-1.21, 16.67+/-1.21, and 19.33+/-3.83, versus 17.00+/-6.90 days, respectively. Histologic assessment at 7 days after transplantation showed that high-dose AEB significantly decreased the histologic rejection score, indicative of decreased inflammatory cell infiltration into the graft. These results suggested that the administration of AEB (medium or high-dose), a PKC inhibitor, mitigated acute rejection and displayed significantly longer MST, similar to high-dose Tac after heterotopic heart transplantation in the rat.ope

The effects of AEB071 (sotrastaurin) with tacrolimus on rat heterotopic cardiac allograft rejection and survival

BACKGROUND: AEB071 (sotrastaurin) is a specific inhibitor of protein kinase C that prevents T-cell activation. Our previous study demonstrated that AEB071 monotherapy could prevent acute cardiac allograft rejection in rats. Herein, we investigated the effects of AEB071 combined with various doses of tacrolimus (Tac) on the allograft rejection and survival in a rat heart transplantation model. MATERIALS AND METHODS: Heterotopic cardiac transplantation from Brown-Norway to Lewis rats was performed. Cardiac allograft survival was assessed by monitoring heartbeats in six recipients of each experimental group. Another four recipient rats were selectively sacrificed in each group at d 7 post-transplantation for histologic examination. Serum transaminases, blood urea nitrogen, and creatinine concentrations were measured. RESULTS: AEB071 monotherapy prolonged allograft mean survival time (MST) compared with the untreated control group. Also a combination of AEB071 and Tac prolonged MST compared with monotherapy groups with higher dose of Tac. In the cardiac graft histology, AEB071 combined with Tac 0.6 mg/kg/d significantly decreased the rejection grade as indicative of decreased inflammatory cell infiltration into the graft. No experimental group was found with any abnormal histologic or serologic evidence of liver and kidney toxicity. CONCLUSION: AEB071 combined with a smaller dosage of Tac may be clinically possible to establish calcineurin inhibitor (CNI) minimization protocol in solid organ transplantation.ope

Microencapsulation of pancreatic islets with canine ear cartilage for immunoisolation

Improving human islet transplantation is often limited by the shortage of donors and the side effects of immunosuppressive agents. If immunoisolation is properly used, it can overcome these obstacles. Because artificial materials are adopted in this technique, however, there are still multiple issues with biocompatibility and foreign body reactions. We developed a chondrocyte microencapsulated immunoisolated islet (CMI-islet) that allows living cells to act as the immunoisolating material. To manufacture CMI-islets for xenotransplantation, isolated rat pancreatic islets were placed on low cell-binding culture dishes. Subsequently, expanded canine auricular cartiage primary cells were seeded on these dishes at a high density and maintained in a suspended state via a shaking culture system. Morphological evaluations showed good islet viability and a clear progression of the islet- encapsulation events. When the cells were challenged with glucose, they were able to secrete sufficient insulin according to glucose concentrations. The CMI-islets responded better to the glucose challenge than did nude pancreatic islets and created better glucose-insulin feedback regulation. Moreover, insulin secretion into the culture medium was confirmed over a period of 100 days, showing the survival and secretory capacity of the CMI-islet cells. By microencapsulating pancreatic islets with recipient ear cartilage cells, long-term insulin secretion can be maintained and the response to glucose challenges improved. This new immunodelusion technology differs from other immunoisolation techniques in that the donor tissue is enclosed with the recipient's tissue, thus allowing the transplanted cells to be recognized as recipient cells. This microencapsulation method may lead to developing viable xenotransplantation techniques that do not use immunosuppressive drugs.ope

Functional evaluation of chondrocyte sheeting immunodelusive immunoisolated bioartificial pancreas

In islet transplantation, encapsulation of immunoisolated islets may provide a way to protect the graft from immune attacks with no immunosuppression. To develop an immunodelusive immunoisolated bioartificial pancreas (BAP), chondrocyte sheets were prepared by cell sheet engineering. We made an immunoisolated BAP encapsulated with rodent-derived chondrocyte sheets and then evaluated its function. Sprague-Dawley rats were used as the source of auricular cartilage and chondrocytes were maintained and expanded by passages. Lewis rats were prepared for islet isolation. A 3-dimensional chondrocyte sheeting immunodelusive immunoisolated BAP (CSI-BAP) was created by multi-layering and unifying the chondrocyte sheets. Subsequently, islets were embedded between each multi-layer sheet. To evaluate the function of the CSI-BAP, a glucose challenge test was performed and secretion of insulin in the culture medium was measured by an enzyme-linked immunosorbent assay. When observed by phase-contrast microscopy, the CSI-BAP maintained close connections between chondrocyte sheets. Islets in the CSI-BAP maintained viability at day 10 and showed good insulin secretion, as revealed by a prompt reaction to increased concentrations of glucose at days 5 and 10. In long-term culture, the CSI-BAP maintained its ability to secrete insulin for 8 weeks. This BAP technology could be an important tool for successful islet transplantation without immunosuppressive drugs.ope

Improved yield and functional parameters of rat pancreas islets isolated under intramuscular anesthesia

Intraperitoneal (IP) anesthesia is commonly used for laboratory animal experiments including rat islet isolation. However, the direct effects of anesthetics on pancreatic islets have been neglected. This study compared the islet function and recovery yield from rats that were anesthetized using IP and intramuscular (IM) injection. In addition, the lag time required to lose deep pain was measured in the following anesthetics combinations. Lewis rats were anesthetized using ketamine and xylazine (K/X) or zoletil and xylazine (Z/X). A glucose challenge test was performed on each group of prepared islets. The effect of the anesthetic agents (e.g., ketamine, zoletil, xylazine alone, and the combination of K/X and Z/X) on cell lines (rat insulinoma; RIN-5F) was investigated by determining their effect on the cell viability, the amount of insulin, and insulin mRNA expression levels of RIN-5F. The time needed for deep anesthesia in IM anesthesia was significantly shortened in comparison to IP [K/X (IM: 313 ± 66 s, IP: 371 ± 84 s) and Z/X (IM: 206 ± 76 s, IP: 245 ± 92 s)]. In addition, number of isolated islet yield by IM anesthesia was significantly improved [K/X (IM: 1530 ± 242, IP: 1245 ± 149) and Z/X (IM: 1136 ± 226, IP: 511 ± 154)]. The functions of fresh islets, indicated by the stimulation index, acquired under IM anesthesia was better preserved than that of IP. The viability and the insulin secretion of RIN-5F were decreased at 24 and 48 h. Insulin gene expression levels were decreased at 24 h as well. Anesthetics may be absorbed through the pancreas surface to the islets and have a direct effect, resulting in islet exposure and deterioration during isolation. In conclusion, for rodent islet isolation, IM anesthesia is simpler and safer in comparison to IP anesthesiaope