Increased vulnerability of pre-existing atherosclerosis in ApoE-deficient mice following adenovirus-mediated Fas ligand gene transfer

Objective The death receptor Fas and Fas ligand (FasL) are present in human advanced atherosclerotic plaques. The activation of the Fas/FasL pathway of apoptosis has been implicated in plaque vulnerability. In the present study, we investigated whether overexpression of FasL in pre-existing atherosclerotic lesions can induce lesion remodelling and rupture-related events. Methods and results Carotid atherogenesis was initiated in apolipoprotein E-deficient mice by placement of a perivascular silastic collar. The resulting plaques were incubated transluminally with recombinant adenovirus carrying FasL (Ad-FasL, lateral) or control β-galactosidase (Ad-LacZ, contralateral). Transfection was restricted to the smooth muscle cell-rich cap of the plaque, and FasL expression led to a three-fold increase in apoptosis in the cap one day after gene transfer. Three days after gene transfer, FasL expression led to a 38% reduction in the number of cap cells. Two weeks after Ad-FasL transfer, non-thrombotic rupture, intra-plaque haemorrhage, buried caps and iron deposits were observed in 6 out of 17 Ad-FasL-treated carotid arteries versus 0 out of 17 controls (P = 0.009), indicative of enhanced plaque vulnerability. Conclusions These data demonstrate that advanced murine plaques are sensitive to Fas/FasL-induced apoptosis, which may indicate that stimulation of this pathway could result in plaque remodelling towards a more vulnerable phenotype.