CXCL12 as innovative immune isolating chemokine for microencapsulated allo and xeno-transplantation in NHPs

摘要

Introduction: We previously demonstrated that a novel alginate encapsulant incorporating the immune-repellent chemokine and islet prosurvivaMactor, CXCL12, can protect and sustain porcine xenoislets in several murine models of diabetes for greater than 200 days post transplant without systemic immune suppression. We have now begun to explore whether a clinical-grade alginate-microencapsulant incorporating CXCL12, can protect and sustain the function of allo and/or adult porcine islets in non-diabetic and ultimately, diabetic non-human primates (NHPs). We are exploring this question in a stepwise fashion through pilot and feasibility studies leading to a final pilot therapeutic study that, if successful, could enable translation of this technology into pivotal NHP studies for an IND. The specific aims of the project are: 1) study of the feasibility of porcine islet implants protected by alginate based CXCL12-eluting xenoislet microcapsules (CEXMs) as a curative treatment for diabetes in NHPs; 2) progressively implement an integrated process of islet microcapsule product generation, evaluation and testing that ensures quality inputs and outputs that can be applied to any alginate microencapsulated islet technology. Materials and Methods: In preliminary studies we transplanted clinical grade microcapsules with or without CXCL12 into the intraperitoneal cavity of healthy NHPs to examine the inflammatory and immune responses to the alginate alone. The reaction to these "blank" capsules was assessed by cytokine assay, flow cytometry, histology and immune histochemistry at day 30 and day 100 post transplant. We then examined transplantation of autologous NHP islets microencapsulated in alginate incorporating CXCL12 into partially pancreatectomized NHPs. In addition to assays described above we also examined explant islet function and immune responses to transplanted islets at 30 and 100 days post transplant. Results and Discussion: Preliminary studies of blank capsule transplants revealed a minimal cytokine, immune and cellular reaction. Intact capsules were readily retrieved from the intraperitoneal cavity by lavage at 30 and 100 days post transplant. Interestingly, capsules containing CXCL12 when found adjacent to mesentery were not surrounded by inflammatory cells in marked contrast to capsules without CXCL12 which were consistently surrounded by a significant inflammatory and fibrotic reaction. The first autologous encapsulated islet transplants with CXCL12 were also performed revealing retrievable capsules at 30 days post transplantation with minimal surrounding infiltration. Studies of the precise inflammatory and immune responses to these capsules are under way. Retrieved encapsulated islets were functional at 30 days post transplantation. While these studies have been ongoing we have been progressively implementing a quality process by which capsules are generated, transplanted and then examined after explantation. Conclusions: The primary finding to date is that microcapsules containing CXCL12 +/- or auto islets with CXCL12 were retrieved and demonstrated an absent or minimal inflammatory or immune response. These data support the next step in our project which includes alloislet transplantation into non diabetic NHPs. Progressive implementation of a quality process has helped regulate all aspects of this project and we believe enhance reproducibility and robustness of datasets at all stages of the study.