Pretransplant islet culture: A comparison of four serum-free media using a murine model of islet transplantation

Introduction. Human islet transplant protocols frequently incorporate a brief period of islet culture before transplantation. The optimal medium for pretransplant islet culture is unknown. Methods. We compared four serum-free media formulated for human islets: Miami (MM1), Memphis (M-SFM), Edmonton (EDM), and Kell OCZEM-SF/AF (Kell). Islets isolated from a single human pancreas with purity > 80% were cultured in 2500-islet-equivalent (IE) fractions using the media listed. After 7 days, each 2500-IE fraction was grafted under the kidney capsule of a streptozocin-diabetic rag1 mouse (n = 4 per group). Mice were evaluated with serum glucose monitoring, stimulated C-peptide release, and glucose tolerance tests. Islet fractions transplanted immediately after isolation (n = 4 mice) served as controls. In vitro islet function was assessed on days 0 and 3 and included insulin release (after static glucose stimulation), total cellular C-peptide content, cell count, and viability. Results. Glucose control was improved in all cohorts of mice after transplant, but only islet grafts cultured in MM1 were statistically indistinguishable from fresh islets. MM1 and hCell-cultured islet grafts showed improved glucose tolerance compared with fresh islets; C-peptide release was similar among the four cohorts. In vitro, only islets cultured in MM1 had similar stimulation index to fresh islets, whereas only hCell- and MM1-cultured islets demonstrated recovery of C-peptide content and insulin release. Conclusions. Media choice before transplant can influence islet quality, even when culture periods are short. Miami MM1 and hCell media may provide better islet protection than alternative media.