Islet transplantation in seminal vesicles restores glycemia in diabetic rats: a preliminary study

Localized Controlled Release of Bilirubin from β-Cyclodextrin-Conjugated ε-Polylysine To Attenuate Oxidative Stress and Inflammation in Transplanted Islets

Islet transplantation has been considered the most promising therapeutic option with the potential to restore the physiological regulation of blood glucose concentrations in type 1 diabetes treatment. However, islets suffer from oxidative stress and nonspecific inflammation in the early stage of transplantation, which attributed to the leading cause of islet graft failure. Our previous study reported that bilirubin exerted antioxidative and anti-inflammatory effects on hypothermic preserved islets, which inspire us to utilize bilirubin to address the survival issue of grafted islets. However, the application of bilirubin for islet transplantation is limited by its poor solubility and fast clearance. In this study, we designed a supramolecular carrier (PLCD) that could improve the solubility of bilirubin and slowly release bilirubin to protect islets after cotransplantation. PLCD was synthesized by conjugating activated β-cyclodextrin (β-CD) to the side chain of ε-polylysine (PLL) and acted as a carrier to load bilirubin via host-guest interactions. The constructed bilirubin supramolecular system (PLCD-BR) significantly improved the solubility and prolonged the action time of bilirubin. In vitro results confirmed that PLCD-BR coculture substantially enhanced the resistance of islets to excessive oxidative stress and proinflammatory stimulation and maximumly maintained the islet function. In vivo, PLCD could prolong drug duration at the transplant site, and the localized released bilirubin could protect the islets from oxidative stress and suppress the production of inflammatory cytokines. Crucially, islet transplantation with PLCD-BR significantly extended the stable blood glucose time of diabetic mice and produced a faster glucose clearance compared to those cotransplanted with free bilirubin. Additionally, immunohistochemical analysis showed that PLCD-BR had superior antioxidative and anti-inflammatory abilities and beneficial effects on angiogenesis. These findings demonstrate that the PLCD-BR has great potentials to support successful islet transplantation.

Syngeneic islet transplantation into seminal vesicles of diabetic rats

Pancreatic islet transplantation has been proposed as an attractive option for the treatment of type I diabetes. Transplantation into different sites has been investigated, among them those that are immuno-logically privileged (e.g., thymus, uterus, brain, anterior eye chamber, and testicle). Because of their characteristics, seminal vesicles could be considered as immunologically privileged organs, but there is no worldwide experience that can confirm it. The purpose of the present study is to assess the viability and functionality of islet transplantation into seminal vesicles of diabetic rats. One hundred ninety inbred adult male syngeneic Lewis rats were used as donors (n = 72), receptors (n = 36), and controls(n = 11). Diabetes was chemically induced through a single intraperitoneal injection of streptozotocin. Groups of 1200 purified islets were introduced in the right seminal vesicle of diabetic rats. Diabetic control rats were sham transplanted. Body weight and glycemia were monitored every 2 d. Of transplanted rats, 16.7% achieved a good function due to islet engraftment, while 30.6% achieved a partially good response, and 52.7% were considered as nonresponding. This is the first report about islet transplantation into seminal vesicles of diabetic animals. Our results indicate that islet transplantation into rat seminal vesicles is technically possible, and that islets can function normally after engraftment into the wall of the seminal vesicle.