Implications of the Patterns of G-Protein Expression Induced in Murine Vein Grafts

Background: Vein grafts heal and remodel through the development of intimal hyperplasia, which can progress to restenosis and occlusion. G-protein coupled receptors are involved in smooth muscle cell proliferation but the role of G-proteins in vein graft remodeling has not been defined. The aim of this study is to characterize the expression of G-proteins in the vein graft and the implication of interruptions of G-protein signaling.
Methods: The murine IVC interposition model was employed. Specimens were perfusion-fixed and sections were stained with H&E and Movat’s stain such that morphometry could be performed using an ImagePro system. Additional specimens of femoral artery were also harvested and snap frozen for western blotting and RT-PCR to allow for the study of G-protein expression. Ungrafted IVCs were used as controls. Additional vessels were immersed in pluronic gel containing the chemical G-protein inhibitors Pertussis Toxin and Gαq inhibitor GP-2A and advenovirus containing mutant Gαi2 and Gαi3, Gαq and Gα12/13 and the Gβγ inhibitor βARK_CT
Results: The vein grafts develop intimal hyperplasia, which is maximal at 28 days and does not change substantially between day 28 and day 56. Cell proliferation peaked at 3 to 7 days. Expression of Gαi3 developed de novo, was detectable by day 3, and continued to increase through day 14. Gαi2, Gαq and Gα12/13 expression increased in a time dependent manner maximal at 14 days. There was a marked time dependent increase in Gβγ over the 28 days. Gαs isoforms (45 and 52kDa) increased from day 7 to day 14. There was no major change in Gαi1 and Gαo over the study period. While inhibition of Gαi2 / Gαi3 and Gαq / Gα12/13 reduced cell proliferation, only inhibition of Gαi2 / Gαi3 reduced the development of intimal hyperplasia. Inhibition of Gβγ inhibited both cell proliferation and intimal hyperplasia.
Conclusions: These data demonstrate that vein graft in the mouse induces a consistent model of remodeling and intimal hyperplasia development and that it is associated with a time dependent increase in G-protein expression. Interruption of G-proteins alters cell kinetics and intimal hyperplasia development.