ObjectiveTo investigate the relationship between aging-induced neointimal formation and Jagged 1 dynamic expression in endothelium after arterial injury in rats. MethodsForty healthy male Sprague-Dawley rats aged 3 months (young adult) and 22 months (old) were selected, and thirty of them were subjected to balloon catheter injury at the thoracic aorta. Morphometry analysis was applied to evaluate neointima/media ratio at 28 days after arterial injury. Immunohistochemistry was used to observe the dynamic expressions of Jaggedl in endothelium and the proliferating cell nuclear antigen (PCNA) in neointima at 7 days, 14 days and 28 days after arterial injury respectively. Cell co-culture system was developed by inoculating endothelial cells(EC) in the upper chamber and smooth musele eells(SMC) in the lower chamber. Fluorescence activated cell sorter (FACS) was used to assay the effect of aging on the expression of Jagged 1 in EC. ＜'3＞H-TdR incorporation and cells counting were used to determine the influence of EC of different ages of rats on platelet derived growth factor (PDGF)-induced proliferation and migration of SMC. ResultsThe neointima/media ratio were obviously higher in old rats than in young rats (0.35±0.02 vs. 0.28±0.01, n=5, P＜0.01). Compared with the young counterparts, old rats showed in immunohistochemistry that the Jaggedl in endothelium displayed a delayed up-regulation and quickly diminished evolvement pattern. The maximal enhancing level of Jaggedl in old rats was much lower than that in young ones. However, the increased extent of PCNA in neointima was significantly higher in old rats than that in young ones. Jagged 1 expression in EC in old rats was significantly lower than that in young one[(46.6±6.3)% vs. (85.4±4.0)%,n=3, P＜0.05]. The SMC co-cultured with EC in old rats exhibited higher proliferation and migration capability than those in young ones after exposure to PDGF of 10ng/ml[2H-TdR incorporation: (26 438±1857) cpm/well vs. (16 698±2076)cpm/well, n=5, P＜0.05. migration:(32±4) cells/field vs. (18±5) cells/field, n=5, P＜0. 05]ConclusionsThe up-regulation of Jaggedl in EC is impaired in aged rats, which is closely related to aging-indueed SMC proliferation and migration. It also suggests that Jagged1 might be involved in the process of aging-exaggerated neointima formation.