Phenotypic Modulation of Cultured Primary Human Aortic Vascular Smooth Muscle Cells by Uremic Serum

Abstract

Patients with chronic kidney disease (CKD) have a markedly increased incidence of cardiovascular disease (CVD). The high concentration of circulating uremic toxins and alterations in mineral metabolism and hormone levels produce vascular wall remodeling and significant vascular damage. Medial calcification is an early vascular event in CKD patients and is associated to apoptosis or necrosis and trans-differentiation of vascular smooth muscle cells (VSMC) to an osteogenic phenotype. VSMC obtained from bovine or rat aorta and cultured in the presence of increased inorganic phosphate (Pi) have been extensively used to study these processes. In this study we used human aortic VSMC primary cultures to compare the effects of increased Pi to treatment with serum obtained from uremic patients. Uremic serum induced calcification, trans-differentiation and phenotypic remodeling even with normal Pi levels. In spite of similar calcification kinetics, there were fundamental differences in osteochondrogenic marker expression and alkaline phosphatase induction between Pi and uremic serum-treated cells. Moreover, high Pi induced a dramatic decrease in cell viability, while uremic serum preserved it. In summary, our data suggests that primary cultures of human VSMC treated with serum from uremic patients provides a more informative model for the study of vascular calcification secondary to CKD.

The Impact of Uremic Toxins on Vascular Smooth Muscle Cell Function

“…The apoptosis of VSMCs promotes atherogenesis, various aspects of plaque instability, intimal calcification, and medial calcification [ 58 , 59 ]. Vessels from pediatric patients on dialysis display extensive VSMC apoptosis [ 60 ], and uremic serum promotes the extensive apoptosis of human VSMCs cultured in vitro [ 9 ]. The apoptotic bodies derived from these VSMCs are known to act as nucleating structures for calcium crystals [ 59 ], and thus promote vascular calcification.…”

“…Indeed, PCS significantly increased the percentage of apoptotic VSMCs in vitro through upregulation of Bax and downregulation of Bcl-2 [ 22 ]. In vitro, high-Pi-induced human VSMC apoptosis (as evidenced by changes in nuclear shape and phosphatidyl-serine externalization) is associated with the increased expression of pro-apoptotic BCL2 family proteins and caspase-3—suggesting a role for the intrinsic pathway [ 9 , 40 ]. These data were confirmed by the observation that high-Pi-induced downregulation of the anti-apoptotic growth-arrest-specific gene 6 and its receptor Axl induced VSMC apoptosis via increased caspase 3 activation [ 62 ].…”

“…Together with the hemodynamic changes observed in CKD, this altered metabolic state promotes deep vascular wall remodeling with intimal hyperplasia, accelerated atherosclerosis, excessive vascular calcification, and vascular stiffness [ 5 , 6 ]. Under uremic conditions, the expression of markers of a contractile VSMC phenotype (such as calponin, SM22α and SMMHC) is dramatically reduced [ 7 , 8 , 9 ] and corresponds to a decrease in aortic constriction [ 8 ]. This phenomenon is associated with changes in VSMC proliferation, apoptosis, migration, and senescence, and the onset of calcification.…”

Superficial Femoral Artery Calcification Is a Novel Risk Factor of Microvascular Complications in T2DM Patients

“…Although our data showed that neither high-TyG index nor FPG was an independent risk factor of SFA calcification, it indicated that under impaired kidney function condition, hyperglycemia may accelerate the development of SFA calcification. It was supported by the fact that the induction of in vitro T2DM calcification model required the high phosphate microenvironment (mimicked the reduced eGFR) [30][31][32]. Vascular calcification was thought to be a manifestation of vascular aging [33].…”

Uremic Toxins and Vascular Calcification–Missing the Forest for All the Trees

“…Osteo-chondrogenesis and VC are driven by stressors including high phosphate, high calcium, oxidative stress, inflammation, senescence, apoptosis and alkalinization [ 21 , 22 ], all (except alkalinization) common manifestations of uraemia. Thus, non-surprisingly, uremic serum accelerates VC in VSMC in vitro [ 23 , 24 , 25 ].…”