Expression of S-phase kinase-associated protein-2 in rat injured aorta and its significance in neointimal hyperplasia

Abstract

Objective To investigate the change of S-phase kinase-associated protein-2 (Skp2) in the aorta of rats after balloon injury and its effect on neointimal hyperplasia.Methods Fisty-six SD male rats were randomly divided into two groups:sham operated group (n =8),and balloon injured group (including:2-,4-,7-,10-,14-and 28-day subgroups,n =8 each).The model of rat aorta injury was established.The vascular tissues were harvested on the postoperative day (POD) 2,4,7,10,14 and 28 respectively and examined histomorphologically.Inmunohistochemistry streptavid-in-peroxidase (SP) method was used to detect the differential expression level of proliferating cell nuclear antigen (PCNA),Skp2 and cyclin dependent kinase inhibitor protein 27 (p27KiP1) at each time point.The expression levels of Skp2 and p27Kip1 mRNA were detected by using real-time quantitative polymerase chain reaction (Real-time PCR).Results (1) The normal artery wall didn' t express PCNA,hut PCNA was detected on POD 2.The amount of positive cells was increased and reached a peak on POD 7 [(38.46 ± 2.01),P ＜ 0.05],then gradually decreased; (2) The expression of Skp2 was very low in uninjured aorta,and increased on POD 2 [(27.90 ±2.37)] and peaked on POD 10 [(47.36 ±2.37),P ＜ 0.05].It was declined on POD 14 and further decreased on POD 28; (3) p27Kip1 was expressed in normal aorta (27.82 ±3.26) and significantly reduced on POD 2 [(14.71 ± 1.37)],significantly increased on POD 10 [(32.06 ± 2.57),P ＜ 0.05] and remained high until POD 28; (4) The expression of PCNA was temporally associated with expression of Skp2 (r =0.892,P ＜ 0.01) ; (5) The Real-time PCR results showed that the expression of Skp2 mRNA was extremely low in normal aorta [(1.28 ± 1.11)],increased on POD 2 and reached the peak on POD 10 [(10.49 ±3.17),P＜ 0.05],then decreased turther on POD 28.The expression of p27Kip1 mRNA could be detected in normal aorta (1.14 ±0.64),decreased on POD 4 (P ＜ 0.05),and remained low from POD 7 to 10,then significantly increased on POD 14 [(1.64 ±0.45),P ＜ 0.05] and returned to normal level on POD 28 (P ＞ 0.05).Conclusion Skp2 was one of the important promoting factors that induced VSMC proliferation and subsequent neointimal hyperplasia. Key words: S-phase kinase-associated protein 2; Artery injury; Vascular smooth muscle cell; Neointimal hyperplasia