| Objective This study was designed to investigate the effect of intrathymic inoculation and jugular vein injection with MSCs on the recipient immunoloregulation and on the discordant rodent Cardiac Xenograft Rejection in the model of guinea pig to rat xenotransplantation. The mechanisms of rejection in xenotransplantation will be explored in the model.Materials and methods MSCs of guinea pig were expanded in medium to the third generation, then inoculated into thymuses gland of rats. Before operation, the recipients were injeceted with MSCs through jugular vein.Donors (guniea pig) and recipients (SD rat) were divided randomly into seven groups. Group A (Control group): The heart from guinea pig was transplanted into the abdomen of SD rat; Group B (CVF group): the recipients were injected with chinese cobra venom factor(CVF) 40u/kg in abdomen and 24 hours later CVF 60u/kg were injected in vein again just before transplantation; Group C (IT+CVF group): 14 days before transplantation, the recipients were inoculated into thymuses gland with 1×105 BMSCs of guniea pig, CVF was injected as group B; Group D (IV+CVF group): the recipients which through jugular vein injected with MSCs of guniea pig 7 days ago were injected with CVF before transplantation as Group B; Group E (IT+IV+CVF group): the recipients received IT and IV, CVF was injected as group B; Group F (IT+IV+CVF+CsA Group): the recipients received CsA(10mg/Kg) in abdomen for 7 days before the transplantation like Group E. Group G (conditioned medium+CVF Group): 3 days before the transplantation, the recipients were injected with conditioned medium through jugular vein, CVF was injected as group B.The grafted heart mean survival time (MST), the mixed cell reaction (MCR), the expression of CCR5, ICAM-1 and the pathology in recipients were observed.Results 1. Pathology: The donor heart in group A showed hyperacute rejection (HAR) change. Delayed xenograft rejection(DXR)change were taken place on other groups. 2. MST(min): Group A:26.8±4.4min, Group B:41±1.2 min, Group C:89.4±8.8 min, Group D:73.6±12.2 min, GroupE组:100.2±6.8 min, Group F:103.4±10.3 min, Group G:44.8±4.9 min. The MST of Group C > Group B ( p<0.05), The MST of Group D> Group B ( p<0.05), The MST of Group E and F were prolonged significantly; The MST of Group E > Group C ( p<0.05), Group F> Group D ( p<0.05); The MST of Group F > Group E but P>0.05. 3. The results of CCR5 in the peripheral blood of recipient's(pg/ml): Group A: 6.76±0.22, Group B: 4.82±0.25, Group C: 2.34±0.84,Group D: 2.88±0.57, Group E: 1.1±0.32, Group F: 1.14±0.23, Group G: 4.08±0.78. Group C and Group D was not particularly different (P> 0.05); Group E and Group F was not particularly different (P> 0.05); the results of CCR5 in group E is much lower significantly than group C and group D ( p<0.05).Conclusions 1. The method of IT+IV with MSCs can upgrade the level of CD4+CD25+ T regulatory cells in rats which can regulate the recipient T cells. 2. This method can derease the level of CCR5, ICAM-1 and prolong the survival time of xenograft. Secretion of IL-2 and IFN-γis inhibited, ratio of Th1/Th2 degrade. It helps to induce immune tolerance. 3. In the model of Cardiac Xenotransplantation of guinea pig-to-rat, IT+IV with MSCs can prolong the MST of xenografts at the same time, but AVR could not be overcomed completely.
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