Overexpression of Soluble Fas Attenuates Transplant Arteriosclerosis in Rat Aortic Allografts

Abstract

Background-The killing of vascular cells by activated macrophages is an important step in the process of destabilization of the arterial wall. The death receptor Fas is implicated in vascular cell death. Hence, we extended our studies in a rat aortic allograft model, using adenovirus-mediated overexpression of soluble Fas (sFas) to block Fas binding to Fas ligand (Fas-L). The contribution of Fas to vascular cell injury and consequent transplant arteriosclerosis was investigated. Methods and Results-Activated monocytes in the presence of macrophage colony-stimulating factor induce endothelial cell apoptosis in vitro, which was significantly inhibited by adenovirus-mediated sFas overexpression. Next, donor rat abdominal aortas were either untreated or transduced with adenoviruses encoding (1) rat soluble Fas (Ad3rsFas), (2) no insert (Ad3Null), and (3) ␤-galactosidase (Ad3nBg). A total of 175 aortic grafts were harvested 2 to 90 days after transplantation. Vascular cell apoptosis and CD45ϩ cell infiltration were significantly reduced in Ad3rsFas-transduced aortas, as compared with control allografts. Moreover, the control allografts developed marked intimal thickening, whereas Ad3rsFas-transduced allografts had significantly less neointima until the 90-day time point. Key Words: arteriosclerosis Ⅲ apoptosis Ⅲ endothelium Ⅲ inflammation Ⅲ gene therapy C ardiac allograft vasculopathy (CAV), characterized by the development of transplant arteriosclerosis, remains the leading cause of late graft failure and patient death in heart transplantation. The archetypal pathological findings of CAV are diffuse concentric intimal proliferation and intense mononuclear cell infiltration, including T cells and macrophages, in most graft vessels. 1,2 Although the precise molecular and cellular mechanisms are not yet elucidated, endothelial cell (EC) injury and recipient inflammatory response are believed to be crucial in the development of CAV. 1,3,4 Increased apoptosis, including vascular EC and smooth muscle cell (SMC), has been observed in acute and chronic rejection; such apoptosis probably is mediated through the Fas/Fas-Ligand (Fas-L) pathway. 5-8 Fas-Lϩ T cells and macrophages bind to Fasϩ vascular cells, inducing apoptosis. One of earliest features of CAV is the adherence of monocytes to the endothelium, followed by their migration into the intima, which may enhance the development of atherosclerotic lesions. 9 Numerous investigations have focused on the molecular mechanism of monocyte attraction and migration into vascular tissues; little attention, however, has been paid to the actual role of infiltrating macrophages in the mediation of CAV. Conclusions-sFasMacrophage colony-stimulating factor (MCSF), which is elevated within inflammatory atherosclerotic lesions, 9 was shown to block spontaneous monocyte apoptosis and to stimulate monocyte differentiation, proliferation, and activation. 10 We have previously reported that monocytes, in the presence of MCSF, switched to a phenotype capable of inducing SMC apoptosis. 11 In ...

Perforin Mediates Endothelial Cell Death and Resultant Transplant Vascular Disease in Cardiac Allografts

“…Recently, inhibition of FasL signaling in a rat model of TVD was reported to partially reduce lesion severity. 25 In addition to this cytotoxic pathway, cytokines secreted by infiltrating T cells, such as ␥-interferon, can cause TVD in the absence of cytotoxicity by indirectly inducing VSMC proliferation. 26 The immunopathological mechanisms that contribute to allograft vascular damage and resultant TVD may involve both acute and chronic rejection processes since acute rejection predicts the development of TVD in humans, and the induction of acute rejection episodes has been shown to markedly increase the severity of TVD in animal models.…”

Modalities and future prospects of gene therapy in heart transplantation

“…This was shown by first placing the donor heart transduced with the Bcl-2 gene in a syngeneic recipient to allow for Bcl-2 gene expression in the graft in the absence of alloimmune responses, with re-transplantation of the graft into an allogeneic recipient 4 days later. In other studies, adenoviral gene transfer of CD40Ig [59], soluble Fas receptor [60], or Fas ligand [61] partially prevented the development of graft vasculopathy. Fas ligand acts by inducing apoptosis of activated T cells that express Fas receptor on their surfaces.…”

Inhibition of neointimal hyperplasia in rats treated with atorvastatin after carotid artery injury may be mainly associated with down-regulation of survivin and Fas expression

“…Luo et al (2001) found that coexpression of p35 in FasLtransduced VSMCs is more potent at inhibiting neointimal formation and as such represents an improved gene therapy approach for restenosis. Wang et al (2002) identified that blocking Fas/Fas-L interaction by overexpression of sFas in graft endothelium inhibited vascular cell apoptosis as well as CD45+ mononuclear cell infiltration, and significantly attenuated the disruption of the arterial wall and transplant arteriosclerosis.…”