Effects of immunosuppressive treatment in prevention of calcification in aortic valved homograft: experiment with rats

Abstract

To investigate the effects of immunosuppressive treatment in prevention of calcification in aortic valved homograft (AVH). 120 Wistar rats were randomly divided into 4 equal groups: Group A (allogene group) undergoing incision of the abdominal aorta and implantation of the AVH with myocardial cuff from SD rats, Group B, injected with cyclosporine A intraperitoneally one day after the implantation, Group C, injected intraperitoneally with anti-dendritic cell monoclonal antibody (DCmAb) one day after the implantation, and Group D (isogenenic or control group), receiving the AVH of another Wistar rats. All groups were further subdivided into 5 equal subgroups to be sacrificed at different time points: 2, 4, 8, 12, and 16 weeks postoperatively. Blood samples were obtained from the vena cava to detect the expression of T-cell antigen receptor (TCR)-alpha and beta and CD28 by flow cytometry. AVH specimens were obtained to observe the changes of endotheliocytes and smooth muscle cells with light and electron microscopy. The expression of CD54 was detected by immunohistochemistry. The calcium content of the AVH tissue after transplantation was examined by flame atomic absorption spectrophotometry. (1) Compared with the isogenic group, the expression levels of TCR-alpha and beta and CD28 in the allogener groups were all significantly higher at all time points (all P < 0.01), peaked 2 approximately 4 weeks after operation, then gradually decreased, and approached the level of the controls 12 weeks after the implantation. Specifically, the expression levels of TCR-alpha and TCR-beta 2 and 4 weeks postoperatively of Group A were 52.4% +/- 3.3% and 43.8% +/- 6.4% respectively, significantly higher than those of Group B [(34.5 +/- 3.5)% and (31.6 +/- 2.6)% respectively], Group C [(31.6 +/- 2.3)% and (29.5 +/- 3.0)% respectively), and Group D (23.2 +/- 1.3)% and (21.6 +/- 2.3)% (all P < 0.01)]; and the CD28 expression level 2 approximately 4 weeks after operation of Group A were (51.7 +/- 7.5)% and (66.3 +/- 4.4)% respectively, both significantly higher than those of Group B [(41.2 +/- 1.6)% and (55.1 +/- 5.1)% respectively], Group C [(36.6 +/- 3.6)% and (51.8 +/- 5.6)% respectively], and Group D [30.7 +/- 1.4)% and (33.3 +/- 0.9)% respectively)] [all P < 0.01 except those levels 12 and 16 weeks after the operation in each subgroup (P > 0.05)] And the levels of TCR-alpha and TCR-beta and CD28 of the 2 treatment groups were all significantly lower than those of the untreated group (Group A) (all P < 0.01). (2) The calcium contents of the AVH tissues of Group A, B, and C significantly increased 4 weeks after the operation and peaked 12 and 16 weeks after operation. No significant difference in calcium level was found in Group D at different time points (all P > 0.05). The calcium contents in AVH tissues 4 and 8 weeks postoperatively of Groups A, B, and C were (2856 +/- 79) microg/g and (3587 +/- 168) microg/g respectively, (2518 +/- 73) microg/g, (3237 +/- 187) microg/g; and (2176 +/- 210) microg/g and (3089 +/- 176) microg/g; all significantly higher than those of Group D (860 +/- 60) microg/g and (870 +/- 50) microg/g respectively, all P < 0.01. Immunosuppressive treatment obviously reduces the immune rejection and delays the course of AVH calcification.