Reluctance of French patients with type 1 diabetes to undergo pig pancreatic islet xenotransplantation.

INTRODUCTION: Type 1 diabetes could possibly be treated by transplantation of pig pancreatic islets. In addition to medical difficulties and ethical problems, social hurdles may need to be overcome. We have evaluated the attitude of patients with type 1 diabetes to the xenotransplantation of pig pancreatic islets and to the potential risks associated with such treatment. METHODS: A survey of 214 patients with type 1 diabetes was carried out in France based on a multiple-choice questionnaire. RESULTS: At first, 52.0% of these patients indicated that they would agree to receive pig islet xenografts. The main sources of reluctance were the ''risk of disease transmission'' (55.5%) and ''risks not yet identified'' (48.7%). After they were told of the risk of cancer or infection associated with immunosuppression, 74.9% of the respondents chose to refuse the transplant, compared with 48.0% before they heard of such risks. A 68.1% would refuse the xenotransplant if it would not exempt them completely from being treated by insulin injections. Discontinuing insulin injections was the most important priority for diabetic patients (73.5%), rather than limitation of diabetes-related complications (52.5%) or increase in life expectancy (44.0%). After they were informed of all of the risks associated with the procedure, 70.5% of the respondents decided they would rather not take any risks, and said they would refuse pig islet transplantation. CONCLUSION: When diabetic patients learned about potential infectious risks and other risks associated with immunosuppression, reluctance to undergo xenotransplantation gained in significance or even led to refusal of the procedure.

AN69 hollow fiber membrane will reduce but not abolish the risk of transmission of porcine endogenous retroviruses.

As the risk of porcine endogenous retrovirus (PERV) infection is a major obstacle to the xenotransplantation of porcine tissue, we investigated whether an AN69 hollow fibre membrane, used for islets of Langerhans transplantation, could prevent the transfer of PERVs and thus reduce the risk of PERV infection. PK15 cells were used as a PERV source. A specific and highly sensitive RCR was used for detection of a PERV provirus DNA (gag region) and a porcine mtDNA. Human U293 cells were incubated in vitro with encapsulated PK15 cells, concentrated encapsulated PK15 supernatant, or concentrated PK15 supernatant as a control. CD1 mice were implanted in vivo with encapsulated PK15 cells or injected with PK15 supernatant. We found no infection in human cells incubated with either encapsulated PK15 supernatant or in 10 out of 11 samples after coincubation with encapsulated PK15 cells. Infection of human cells was, however, detected in 1 out of 11 samples after coincubation with encapsulated PK15 cells. The presence of PERV provirus DNA and porcine mtDNA was detected in all the investigated tissues of the mice injected with PK15 supematant and in various tissues of the mice implanted with encapsulated PK15 cells. Four weeks after the last injection of PK15 supernatant or a fiber explantation, no mouse showed any presence of PERV provirus DNA or porcine mtDNA. Our results demonstrate that AN69 hollow fiber membrane will reduce but not abolish the risk of PERV infection. Because the real risk of PERV infection still remains unknown, it is necessary to investigate further the real protection that could be provided by hollow fibers to ensure the safety of clinical xenotransplantation.

In vitro induction of inhibitory macrophage differentiation by granulocyte-macrophage colony-stimulating factor, stem cell factor and interferon-gamma from lineage phenotypes-negative c-kit-positive murine hematopoietic progenitor cells.

CD11b+Gr-1+ inhibitory macrophages (iMacs) were implicated in profound depression of T cell functions sometimes observed during cyclophosphamide treatments and overwhelming infections, through a secretion of nitric oxide (NO). Myeloid origin and maturation stages of iMacs are still unknown. As tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) contributed crucially to the activation of inducible NO synthase (iNOS) gene transcription and to the differentiation of macrophages, we tested their roles in the induction of iMacs differentiation from bone marrow hematopoietic progenitor cells (HPC) of uncompromised mice. Lineage phenotypes-negative (lin)) c-kit+ cells of Balb/c mice were cultured 6 days with granulocyte-macrophage colony-stimulating factor (GM-CSF), stem cell factor (SCF, c-kit ligand) in presence or not of TNF-alpha or IFN-gamma. CD11b+Gr-1+ cells only derived in presence of [GM-CSF + SCF + TNF-alpha] or [GM-CSF + SCF + IFN-gamma] could express iNOS upon in vitro stimulation with [IFN-gamma + TNF-alpha] or [IFN-gamma + LPS] known to boost iNOS expression in murine macrophages. However, whereas [GM-CSF + SCF + TNF-alpha] induced only weakly iMacs generation and contributed also to the differentiation of CD11b+Gr-1-CD11c+ myeloid dendritic cells, [GM-CSF + SCF + IFN-gamma] induced exclusively and importantly iMacs differentiation. Moreover [GM-CSF + SCF + IFN-gamma]-generated iMacs were more mature than [GM-CSF + SCF + TNF-alpha]-derived iMacs since IFN-gamma increased more strongly CD11b+Gr-1+ cells expressing Ly-6C and generated lesser cells expressing MHC class II and CD86 molecules. Finally [GM-CSF + SCF + IFN-gamma]-generated CD11b+ cells showing a powerful suppressive activity on T cell proliferations, correlated with NO secretion. In conclusion, our study showed, for the first time, that IFN-gamma induced very efficiently the differentiation of functional iMacs from lin- c-kit+ murine HPC in vitro, and indicated clearly that iMacs progenitors may be present in bone marrow of naïve mice.