Inhibition of transforming growth factor-β restores endothelial thromboresistance in vein grafts

Abstract

Background Thrombosis is a major cause of the early failure of vein grafts (VGs) implanted during peripheral and coronary arterial bypass surgeries. Endothelial expression of thrombomodulin (TM), a key constituent of the protein C anticoagulant pathway, is markedly suppressed in VG after implantation and contributes to local thrombus formation. While stretch-induced paracrine release of transforming growth factor-β (TGF-β) is known to negatively regulate TM expression in heart tissue, its role in regulating TM expression in VGs remains unknown. Methods Changes in relative mRNA expression of major TGF-β isoforms were measured by qPCR in cultured human saphenous vein smooth muscle cells (HSVSMC) subjected to cyclic stretch. To determine the effects of paracrine release of TGF-β on endothelial TM mRNA expression, human saphenous vein endothelial cells (HSVEC) were co-cultured with stretched HSVSMC in the presence of 1D11, a pan-neutralizing TGF-β antibody, or 13C4, an isotype-control antibody. Groups of rabbits were then administered 1D11 or 13C4 and underwent interpositional grafting of jugular vein segments into the carotid circulation. The effect of TGF-β inhibition on TM gene expression was measured by qPCR, protein C activating capacity and local thrombus formation were measured by in situ chromogenic substrate assays, and VG remodeling was assessed by digital morphometry. Results Cyclic stretch induced TGF-β1 expression in HSVSMC by 1.9±0.2-fold, P<.001 without significant chang in the expressions of TGF-β2 and TGF-β3. Paracrine release of TGF-β1 by stretched HSVSMC inhibited TM expression in stationary HSVEC placed in co-culture by 57±12%, P=.03, an effect that was abolished in the presence of 1D11. Similarly, TGF-β1 was the predominant isoform induced in rabbit VGs 7 days after implantation (3.5±0.4-fold induction, P<.001). TGF-β1 protein expression localized predominantly to the developing neointima and coincided with marked suppression of endothelial TM expression (16±2% of vein controls, P<.03), a reduction in situ APC-generating capacity (53±9% of vein controls, P=.001) and increased local thrombus formation (3.7±0.8-fold increase over vein controls, P<.01). External stenting of VGs to limit vessel distension significantly reduced TGF-β1 induction and TM downregulation. Systemic administration of 1D11 also effectively prevented TM downregulation, preserved activated protein C-generating capacity and reduced local thrombus in rabbit VGs without observable effect on neointima formation and other morphometric parameters 6 weeks after implantation. Conclusion TM downregulation in VGs is mediated by paracrine release of TGF-β1 caused by pressure-induced vessel stretch. Systemic administration of an anti-TGF-β antibody effectively prevented TM downregulation and preserved local thromboresistance without negative effect on VG remodeling.

Targeting the TGFβ signalling pathway in disease

“…The exact mechanism of action of TGFβ signalling in intimal hyperplasia and subsequent graft failure is unclear, but it is speculated that TGFβ1 contributes at multiple steps, including EMT, promotion of fibroblast, endothelial and vascular smooth muscle cell proliferation, increased collagen synthesis and deposition, and induction of fibrosis 177 . Soluble forms of the small, leucine-rich proteoglycans decorin and fibromodulin, which possess TGFβ-antagonist activity, exhibit potent intimal hyperplasia-suppressing effects in cultured human saphenous vein, offering the potential for therapeutic benefit after coronary artery bypass surgery 178-180 . The novel pyrrole-imidazole polyamide drug class, targeted to suppress TGFB1 gene transcription, showed efficacy in reducing neointimal hyperplasia and stimulating re-endothelialization of carotid arteries in a preclinical model of arterial injury 50 .…”

Retracted: Transforming Growth Factor Beta‐1 Promotes Smooth Muscle Cell Proliferation and Migration in an Arteriovenous Fistulae: The Role of Wall Shear Stress

“…Several studies have shown that TGF-β1 is an important mediator of intimal hyperplasia in vascular diseases (16). A study found that in balloon injured arteries, TGF-β1 has an important role in neointimal…”

The Role of TGF-β Signaling in Saphenous Vein Graft Failure after Peripheral Arterial Disease Bypass Surgery

“…TGF-β inhibitors are now widely used with success in the cancer field [ 96 , 97 ]. Some results have also been obtained in extensive basic trials in the prevention of intimal hyperplasia, so TGF-β appears to be promising in intimal hyperplastic disease [ 77 , 98 , 99 ]. We extracted data from (accessed on 15 June 2023) regarding vascular injury and TGF-β, which are compiled in Table 4 .…”