Effects Of Plerixafor Combined With Rapamycin Or Cyclosporine A On Heart Transplantation

Objective:The effects of different combinations of Plerixafor(Pler)combined with Cyclosporin A(CsA)or Rapamycin(R)on survival after heart transplantation in mice were investigated in an animal model of heart transplantation.Method:Male C57BL/6J mice and inbred strains of male BALB/c mice were selected as the receptors and donors in the in vivo cardiac transplantation model,respectively.1 mg/kg Plerixafor(P1),0.4 mg/kg R or 20 mg/kg CsA were clinical routine doses.Subcutaneous administration of P1 only or combined with intraperitoneal administration of CsA or R were performed in mice.After the single dose of P1,changes of white blood cell(WBC)count and lymphocyte(LY)count were absolute cell number.Moreover,their changes after 14 days of administration of both P1+R and R alone were detected as well.The median surviving time(MST),survival curves,mean palpation score(MPS)after cardiac transplantation,expressions of regulatory cells(Tregs)and their main components,immunohistochemical staining of Fox P3and H&E staining of mouse heart sections were detected to assess the survival of mice following cardiac transplantation.Result:The counts of WBC and LY at 0,1,2,3,and 4 hours after a single subcutaneous injection of P1 in normal mice.The WBC counts of the conventional clinical dose of P1 were respectively 3975±549/mm~3,7375±278/mm~3,8875±165/mm~3,9200±1496/mm~3and 6900±580/mm~3.LY counts at 0,1,2,3,and 4 hours after a single subcutaneous injection of P1 were 3762±291/mm~3,5128±226/mm~3,5393±205/mm~3,6357±1116/mm~3,5442±393/mm~3.The WBC counts of the recipient mice 14 days after transplantation were 10220±1277/mm~3in the P1+R group,4217±681/mm~3in the R group,and 3975±549/mm~3in the blank control group.MST was 7.4 days for the blank group,10 days for P1,40.4 days for R,and 70 days for the combination(p<0.01).The mean survival was 19 days in the CsA alone group and 16 days in the CsA plus P1 group.14-day palpation score.14 days after transplantation,the MPS was 1.41±0.13,2.68±0.04,1.95±0.11,1.93±0.33,2.94±0.05,2.97±0.04 in the control,CsA,P1,P1+CsA,R,and P1+R groups,respectively.The positive rate of peripheral blood Tregs in group R and group P1+R was5.3±0.67/mm~2,and 9.1±1.49/mm~2,respectively,and that in isolated spleen Tregs was 21.28±1.423/mm~2and 22.07±1.456/mm~2,respectively.After 14 days of cardiac transplantation,immunohistochemical staining showed that most of Tregs were positive strained with Fox P3(Fox P3-stained cells).The mean number of Fox P3-stained cells in each high-power field(HPF)of P1+R group and R group was 26.10±2.294/mm~2,and 7.44±1.978/mm~2,respectively.Fourteen days after transplantation(8 days in the control group and the P1 group),mice were stained with H&E to determine the degree of myocardial injury after heart transplantation.Multifocal inflammatory infiltrates,interstitial edema and myocardial cell hemorrhage were observed in the CsA+P1 group.Only mild infiltration and slight interstitial edema were seen in the R and P1+R groups.Conclusion:Pler alone prolonged the survival of mouse heart grafts.Pler combination with R can prolong the survival of mouse heart grafts by co-inducing regulatory T cell Fox P3 production.CsA alone significantly prolonged cardiac graft survival,but the combination of CsA and Pler decreased the graft survival.