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Improving islet transplantation outcome by CXCR1/CXCR2 inhibition

Antonio Citro¹, Elisa Cantarelli¹, Erica Dugnani¹, Luisa Daffonchio², Marcello Allegretti², Lorenzo Piemonti¹

¹San Raffaele Scientific Institute, Diabetes Research Institute (HSR-DRI), Milan; ²Dompè Spa, Research and Development Department, Aquila, Italy

Objective: The aim of our work is to determine whether the CXCR1/CXCR2 inhibition improves islet transplantation outcome.

Methods and Results: Liver inflammatory status was studied before and after intrahepatic transplantation (Tx) of 500 syngeneic islets in diabetic C57BL/6 mice. Cytokine and chemokine transcripts 4h-24h-48h after Tx were determined using RNAse protection assays. Intrahepatic leucocyte (IHL) infiltration 1, 3, 5, 7, 10, 14 days after Tx was determined by FACS. The intrahepatic mRNA for CXCL1/KC was strongly induced immediately after islet infusion (100-fold increase after 4h). Polimorfonuclear cells (Gr1+/CD11b+/Ly6C-; PMN, 100% CXCR2+) was the first leucocytes subpopulation infiltrating the liver. To evaluate whether the block of CXCL1-CXCR2 axis improve islet engraftment, 400 syngeneic islets were alternatively transplanted in diabetic CXCR2-/- or CXCR2+/+ Balb/C mice. The absence of CXCR2 led to a significant improvement of transplant function. On this basis we tested whether Reparixin, a CXCR1/CXCR2 allosteric inhibitor, is able to improve islet transplantation outcome. In syngeneic marginal mass model of 250 islet Tx in diabetic C57BL/6 mice the probability and median time to reach euglycaemia were 100% and 2 days for Reparixin treated mice (n=29) as compared to 58% and 50 days for vehicle treated mice (n=34) (p<0.001). In an allogeneic full mismatched model of islet Tx (400 Balb/c islets infused in diabetic C57BL/6 mice) Reparixin significantly prolonged the time to rejection: median survival time 12+0.6 days (n=13) and 8+1.3 days (n=7) respectively for Reparixin and vehicle treated mice (p<0.007). Islet survival time was further improved using Reparixin in combination with Rapamycin+FK-506 or MMF+FK-506. In both models Reparixin treatment was associated to a decrease PMN and NKT cells (NK1.1+/CD3+) liver infiltration.

Conclusion: Inhibition of CXCR1/CXCR2 is crucial for improving islet engraftment and survival. On this basis a clinical trial (NCT01220856) is ongoing testing Reparixin in association with the conventional immunosuppressive therapy.