Differential Regulation of Hyaluronic Acid Synthase Isoforms in Human Saphenous Vein Smooth Muscle Cells

Abstract

Abstract-Autologous saphenous vein bypass grafts (SVG) are frequently compromised by neointimal thickening and subsequent atherosclerosis eventually leading to graft failure. Hyaluronic acid (HA) generated by smooth muscle cells (SMC) is thought to augment the progression of atherosclerosis. The aim of the present study was (1) to investigate HA accumulation in native and explanted arterialized SVG, (2) to identify factors that regulate HA synthase (HAS) expression and HA synthesis, and (3) to study the function of the HAS2 isoform. In native SVG, expression of all 3 HAS isoforms was detected by RT-PCR. Histochemistry revealed that native and arterialized human saphenous vein segments were characterized by marked deposition of HA in association with SMC. Interestingly, in contrast to native SVG, cyclooxygenase (COX)-2 expression by SMC and macrophages was detected only in arterialized SVG. In vitro in human venous SMC HAS isoforms were found to be differentially regulated. HAS2, HAS1, and HA synthesis were strongly induced by vasodilatory prostaglandins via G s -coupled prostaglandin receptors. In addition, thrombin induced HAS2 via activation of PAR1 and interleukin 1␤ was the only factor that induced HAS3. By small interfering RNA against HAS2, it was shown that HAS2 mediated HA synthesis is critically involved in cell cycle progression through G 1 /S phase and SMC proliferation. In conclusion, the present study shows that HA-rich extracellular matrix is maintained after arterialization of vein grafts and might contribute to graft failure because of its proproliferative function in venous SMC. Furthermore, COX-2-dependent prostaglandins may play a key role in the regulation of HA synthesis in arterialized vein grafts. Key Words: hyaluronic acid Ⅲ extracellular matrix Ⅲ cyclooxygenase-2 Ⅲ vein graft stenosis A utologous saphenous vein grafts (SVG) are frequently used for bypass grafting in patients with symptomatic occlusive disease of coronary arteries or arteries of the lower extremities. Subsequently, the grafted vein segments are exposed to arterial blood pressure and shear stress, which are thought to initiate intensive remodeling, intimal thickening, in-graft thrombosis, and superimposed atherosclerosis associated with long-term failure rates of approximately 30% to 40%. 1,2 The pathophysiological mechanisms eventually resulting in graft failure include activation and dedifferentiation of vascular smooth muscle cells (SMC) from a contractile into a secretory phenotype characterized by high migratory and proliferative activity. 3 In addition, the extracellular matrix (ECM) undergoes remodeling in arterialized venous grafts. This remodeling is characterized by high ECM turnover conferred by matrix metalloproteinases 1, -2, and -9 4,5 and increased deposition of newly synthesized ECM components including collagen and proteoglycans. 6,7 ECM remodeling is thought to be required for the proliferative and migratory activation of SMC and to support intimal volume expansion. 8 Recently, hyaluronic acid (HA) has b...

Hyaluronan-CD44-ERK1/2 Regulate Human Aortic Smooth Muscle Cell Motility during Aging

“…Moreover, it is to be considered that young cells for the in vitro data came from a young, but mature donor whereas RNA for the in vivo experiments came from fetal tissues. Previous work showed that HAS1 together with HAS2 are the more abundant HAS isoforms expressed in saphenous vein, whereas SMCs isolated from the same vessel expressed mainly HAS2 and HAS3 (41). Even if a clear correlation is not reported in the literature between age and GAG content in the ECM of vessels (30), other studies reported an age increase of HA in aorta bifurcation (42) and in cerebral arteries (43).…”

The effects of 4-methylumbelliferone on hyaluronan synthesis, MMP2 activity, proliferation, and motility of human aortic smooth muscle cells

“…In SMCs, HAS2 silencing by siRNA decreased cell proliferation (van den Boom et al 2006). Moreover, HAS2 expression was modulated by pharmacological treatments (Sussmann et al 2004), indicating a fine control of the expression of this enzyme.…”

Modulation of Hyaluronan Synthase Activity in Cellular Membrane Fractions

“…Cells treated with PMA, IL-1␤, or PDGF-BB increase the amount of HA released into the culture medium (29,54,55), whereas treating cells with 4-MU decreases synthesis of HA (56). We tested the effects of these compounds on HAS activity in the PM and CM fractions.…”