OBJECTIVETo observe the influence of guinea pig mesenchymal stem cells (MSCs) culture in vitro on the immunological status in heterogeneous recipient, and to evaluate the immunomodulation of MSCs to the immune rejection of liver xenotransplantation.

METHODSThe mononuclear cell fraction obtained by centrifugation over Percoll was cultured in vitro. Cell surface epitopes were analyzed by flow cytometry technique, and MSCs were incubated at the addition of adipocyte induction media, and stained in Oil Red O. The immunoglobulin and complement in rat recipient serum were assayed after infusion of donor MSCs. Thirty guinea pigs and thirty Wistar rats were randomly divided into three groups. All rat recipients undertook cyclophosphamide (CTX) infusion. Group A was MSCs infusion group, group B was saline infusion group and group C was dexamethasone (DXM) infusion group. Orthotopic guinea pig to rat liver transplantation model was established. The survival time and the immunopathology of graft were observed.

RESULTSAccording to flow cytometry assay, MSCs were positive for CD44 and CD29, while negative for CD34 and CD45. Lipid droplets were found in the MSCs cytoplasm after being incubated in adipogenic inducation media. The concentrations of IgG, IgM, C3 at all time point after MSCs infusion were significantly decreased than before (P < 0.05), while the concentrations of IgA and C4 did not changed. The survival time of group A (431 +/- 27 min) was obviously longer than group B (148 +/- 16 min) and group C (141 +/- 22 min) (P < 0.01). The intense hyperacute rejection rapidly occurred of group B and C after blood re-perfusion. The severe immunopathological injury could be observed at the grafts of group B and C. However, the hyperacute rejection of group A occurred slightly.

CONCLUSIONSMSCs can be identified by virtue of cell morphology, membrane phenotype and differential potential. MSC may play a role in the immunosuppression in hyperacute rejection in the liver xenotransplantation.