Operational tolerance (graft acceptance in an immunosuppression (IS)-free environment) after living-donor liver transplantation (LDLT) could occur by our elective protocol in some patients. There is, nevertheless, no reliable parameter to monitor patients who may discontinue IS without a risk of rejection. To identify such parameters, we systemically phenotyped peripheral blood mononuclear cells from operationally tolerant patients. An increase was observed in the frequency of CD4 + CD25 high+ cells, B cells and Vd1/Vd2 cdT-cells ratio in operationally tolerant patients (Gr-tol; n = 12), compared with those from age-matched volunteers (Gr-vol; n = 24) or patients on IS (Gr-IS; n = 19). The frequency of NK cells was decreased in Gr-tol, compared with those in Gr-IS or Gr-vol. The frequency of NKT cells was decreased after LDLT, compared with that in Gr-vol. Although the contribution of those subsets to the tolerant state remains elusive, the results may provide important clues for reliable indicators of tolerance after LDLT.

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Islet allotransplantation can achieve insulin independence in patients with type I diabetes. Recent reports show that the two-layer method (TLM), which employs oxygenated perfluorochemical (PFC) and UW solution, is superior to simple cold storage in UW for pancreas preservation in islet transplantation. However, UW solution has several disadvantages, including the inhibition of Liberase activity. In this study, we investigated the features of a new solution, designated M-Kyoto solution. M-Kyoto solution contains trehalose and ulinastatin as distinct components. Trehalose has a cytoprotective effect against stress, and ulinastatin inhibits trypsin. In porcine islet isolation, islet yield was significantly higher in the M-Kyoto/PFC group compared with the UW/PFC group. There was no significant difference in ATP content in the pancreas between the two groups, suggesting that different islet yields are not due to their differences as energy sources. Compared with UW solution, M-Kyoto solution significantly inhibited trypsin activity in the digestion step; moreover, M-Kyoto solution inhibited collagenase digestion less than UW solution. In conclusion, the advantages of M-Kyoto solution are trypsin inhibition and less collagenase inhibition. Based on these data, we now use M-Kyoto solution for clinical islet transplantation from nonheart-beating donor pancreata.

Although application of the Edmonton protocol has markedly improved outcomes for pancreatic islet transplantation, the insulin independence rate after islet transplantation from one donor pancreas has proven to remain low. During the isolation process and subsequent clinical transplantation, islets are subjected to severe adverse conditions that impair survival and ultimately contribute to graft failure. Pancreas preservation with the two-layer method (TLM) has proven to improve transplant results by protecting isolated islets against apoptosis through the mitochondrial pathway. However, pancreas storage with TLM cannot protect against activation of c-Jun NH 2 -terminal kinase (JNK) in isolated islets. This study investigated whether delivery of a JNK inhibitory peptide (JNKI) via the protein transduction system can prevent apoptosis of islet cells immediately after isolation. For efficient delivery of the (JNKI into isolated islets, we synthesized JNKI as a C-terminal fusion peptide with the 11-arginine protein transduction domain (11R-JNKI). 11R efficiently delivered the JNKI into isolated islets and 11R-JNKI prevented islet apoptosis immediately after isolation and improved islet graft function. These findings suggest that peptide drugs could be useful for the prevention of the impairment of islet † These authors contributed equally to this study. cells and lead to improvement in the outcomes for pancreatic islet transplantation.