Objective    To explore the role of gap junctions on the interaction between endothelial cells and smooth muscle cells in a coculture system.     Methods    Rat aortic endothelial cells (RAECs) and smooth muscle cells

(SMCs) were isolated and primarily cultured from rat aortic wall tissue and identified by immunofluorescence staining with vWF and smooth muscle α-actin respectively. A coculture system was established by seeding SMCs and ECs in the each side of Transwell  insert respectively and their growth was observed by transmission electron microscopy. Then

the proliferation of SMCs was evaluated by

3

H-TdR incorporation. Meanwhile

18α-glycyrrhetinic acid (18α-GA)

a specific blocker of gap junction

was administered to observe its effect on the proliferation of SMCs in the coculture system. A Transwell insert system with SMCs in both well and Transwell served as control.     Results    The ECs and SMCs grow well and attached together to form gap junctions in the coculture system. On the first day after coculture

there was no significantly difference of

3

H-TdR incorporation between ECs/SMCs and SMCs/SMCs (P0.05). On the second day

SMCs/SMCs system had a higher incorporation value of

3

H-TdR than ECs/SMCs system

though there was no statistical difference.  On the third day

the incorporation value in ECs/SMCs was significantly lower than that of SMCs/SMCs system (P0.05)

suggesting that ECs suppressed SMCs proliferation. However

when SMCs in the culture well was treated with 50 μmol/L 18α-GA for 24 h

the incorporation value of

3

H-TdR of ECs/SMCs system was significantly higher than that of the ECs/SMCs system without treatment (P0.05)

indicating that 18α-GA suppressed the inhibitory effect of ECs on SMCs proliferation.     Conclusion    ECs may suppress the proliferation of SMCs via gap junctions.