A novel prevascularized tissue-engineered chamber as a site for allogeneic and xenogeneic islet transplantation to establish a bioartificial pancreas

Abstract

Although sites for clinical or experimental islet transplantation are well established, pancreatic islet survival and function in these locations remain unsatisfactory. A possible factor that might account for this outcome is local hypoxia caused by the limited blood supply. Here, we modified a prevascularized tissue-engineered chamber (TEC) that facilitated the viability and function of the seeded islets in vivo by providing a microvascular network prior to transplantation. TECs were created, filled with Growth Factor-Matrigel™ (Matrigel™) and then implanted into the groins of mice with streptozotocin-induced diabetes. The degree of microvascularization in each TECs was analyzed by histology, real-time PCR, and Western blotting. Three hundred syngeneic islets were seeded into each chamber on days 0, 14, and 28 post-chamber implantation, and 300, 200, or 100 syngeneic islets were seeded into additional chambers on day 28 post-implantation, respectively. Furthermore, allogeneic or xenogeneic islet transplantation is a potential solution for organ shortage. The feasibility of TECs as transplantation sites for islet allografts or xenografts and treatment with anti-CD45RB and/or anti-CD40L (MR-1) was therefore explored. A highly developed microvascularized network was established in each TEC on day 28 post-implantation. Normalization of blood glucose levels in diabetic mice was negatively correlated with the duration of prevascularization and the number of seeded syngeneic islets. Combined treatment with anti-CD45RB and MR-1 resulted in long-term survival of the grafts following allotransplantation (5/5, 100%) and xenotransplantation (16/20, 80%). Flow cytometry demonstrated that the frequency of CD4+Foxp3-Treg and CD4+IL-4+-Th2 cells increased significantly after tolerogenic xenograft transplantation, while the number of CD4+IFN-γ-Th1 cells decreased. These findings demonstrate that highly developed microvascularized constructs can facilitate the survival of transplanted islets in a TECs, implying its potential application as artificial pancreas in the future.

Bioengineering the Vascularized Endocrine Pancreas: A Fine-Tuned Interplay Between Vascularization, Extracellular-Matrix-Based Scaffold Architecture, and Insulin-Producing Cells

“…They were positioned in a silicone cylinder tubing at the mouse groin, which was closed at the distal end with inguinal fat and completely sealed with bone wax. The study showed the ability of the chamber to obtain a microvascularized network after 28 days and to sustain the engraftment and function of syngeneic islets after 10–14 days ( 101 , 102 ). However, the use of Matrigel in clinical procedures has some shortcomings related to its poorly defined chemical composition ( 25 ).…”

Enhancing Pancreatic B-Cell Viability and Longevity Through Novel Microencapsulation Strategies and Stromal Cell Support

“…Another approach currently undertaken is by using a preimplantation period to allow vascularization of an immunoisolated device or of a scaffold that can bear immunoisolated islets [100,101]. In the preimplantation strategy, the immunoisolating device is first implanted to allow neovascularization and afterwards immunoisolated islets are introduced [100,102]. In one of these approaches, basic fibroblast growth factor (bFGF)/sodium hyaluronateimpregnated bioabsorbable gelatin sheets were implanted subcutaneously, followed by islet transplantation 7 days after administering the bFGF mixture.…”

“…Administration of monoclonal antibody (mAbs) that specifically target molecules associated with immune reactions has been shown to prolong graft survival of various organs and tissues [133]. The mAbs include anti-CD40 mAb, anti-CD154 mAb, and anti-lymphocyte functionassociated antigen 1 (LFA-1) mAb [102,[154][155][156]. Short-term administration of anti-LFA-1 mAb combined with conformal PEG coating encapsulation synergistically elevated graft survival rates to 78% by decreasing immune cell recruitment, suppressing proinflammatory cytokines, and enhancing macrophage polarization towards an immunosuppressive M2 phenotype [155].…”