Thursday October 21, 2021 - 15:45 to 17:05
Co-localized immune protection using cyclosporine A eluting micelles in a murine islet allograft model
Purushothaman Kuppan1, Sandra Kelly1, Kateryna Polishevska1, Karen Seeberger1, Mandy Rosko1, Gregory S. Korbutt1, Andrew R. Pepper1.
1Alberta Diabetes Institute, Department of Surgery, University of Alberta, Edmonton, AB, Canada
Dr. Pepper and Dr. Korbutt.
Introduction: Islet transplantation is a promising therapeutic strategy to restore physiologic glycemic control to patients with type 1 diabetes. However, factors such as chronic auto- and allo-immune responses and also, the diabetogenic effects of systemic immunosuppression contribute to long-term islet graft failure. Herein, we explore the utility of localized islet graft drug delivery to modulate the inflammatory and adaptive immune responses. Poly(lactic-co-glycolic acid) (PLGA)is an attractive biomaterial, which has widely been used to make drug delivery vehicles. Cyclosporine A (CsA) is a potent immunosuppressant, which is clinically used in the prevention of transplant rejection. Therefore, our aim is to encapsulate CsA in PLGA micelles as a means to deliver localized immunosuppression at the transplant site to improve the islet allograft function.
Method: PLGA and CsA solution mixtures were emulsified using polyvinyl alcohol (PVA) and stirred for an hour to evaporate the organic solvent which allows the micelles particles to harden. Micelles were collected and freeze dried. Encapsulation efficiency and drug release kinetics were analyzed using high-performance liquid chromatography (HPLC). Further, the cytoprotective capacity of the CsA loaded micelles were tested in a syngeneic transplant study (500 BALB/c islets transplanted into the diabetic BALB/c mice) (n=3). Subsequently, a series of allogeneic mouse islet transplants were conducted by co-delivering BALB/c islets (500 islets) with either 4 mg (10 mg/kg of CsA) CsA micelles (n=7) or empty micelles (n=8) under the kidney capsule of diabetic C57BL/6 mice. In addition, CsA +/- micelles groups were administered with CTLA4-Ig (10 mg/kg) intraperitoneally on days 0, 2, 4, and 6 posttransplant. After transplantation, recipient's blood glucose was monitored 3 times per week. Allograft rejection was defined as two consecutive readings ≥18.0 mmol/L.
Results: All recipients from the syngeneic + CsA micelles group became euglycemic and demonstrated robust glucose clearance in response to a metabolic challenge; confirming that localized CsA micelles are non-toxic. Recipients of CsA micelles, had significantly delayed islet allograft rejection as a monotherapy compared to islets alone (p<0.05). Furthermore, 54% (6 out of 11) of CsA micelle recipients showed long-term (>214 days) allograft survival when combined with CTLA4-Ig therapy, compared to 25% (2 out of 8) of CTLA4-Ig alone (p=0.13). An intraperitoneal glucose tolerance test (IPGTT) at 100 days posttransplant demonstrated that the recipient’s of both CSA+CTLA4-Ig and CTLA4-Ig alone groups had a comparable glucose tolerance (p> 0.05,).
Conclusion: Our study demonstrates that localized CsA drug delivery via micelles elution provides a feasible therapeutic platform to locally deliver immunomodulatory drugs in a controlled and favorable manner, thereby promoting a protective transplant niche for both syngeneic and allogeneic islets.