Defining outcomes for β-cell replacement therapy in the treatment of diabetes: a consensus report on the Igls criteria from the IPITA/EPITA opinion leaders workshop by Rickels, MR, Stock, PG, De Koning, EJP, Piemonti, L, Pratschke, J, Alejandro, R, Bellin, MD, Berney, T, Choudhary, P, Johnson, PR, Kandaswamy, R, Kay, TWH, Keymeulen, B, Kudva, YC, Latres, E, Langer, RM, Lehmann, R, Ludwig, B, Markmann, JF, Marinac, M, Odorico, JS, Pattou, F, Senior, PA, Shaw, JAM, Vantyghem, M-C, White, S