Replicative senescence of vascular smooth muscle cells enhances the calcification through initiating the osteoblastic transition

Abstract

Medial artery calcification, which does not accompany lipid or cholesterol deposit, preferentially occurs in elderly population, but its underlying mechanisms remain unclear. In the present study, we investigated the potential role of senescent vascular smooth muscle cells (VSMCs) in the formation of senescence-associated medial calcification. Replicative senescence was induced by the extended passages (until passages 11-13) in human primary VSMCs, and cells in early passage (passage 6) were used as control young cells. VSMC calcification was markedly enhanced in the senescent cells compared with that in the control young cells. We identified that genes highly expressed in osteoblasts, such as alkaline phosphatase (ALP) and type I collagen, were significantly upregulated in the senescent VSMCs, suggesting their osteoblastic transition during the senescence. Knockdown of either ALP or type I collagen significantly reduced the calcification in the senescent VSMCs. Of note, runt-related transcription factor-2 (RUNX-2), a core transcriptional factor that initiates the osteoblastic differentiation, was also upregulated in the senescent VSMCs. Knockdown of RUNX-2 significantly reduced the ALP expression and calcification in the senescent VSMCs, suggesting that RUNX-2 is involved in the senescence-mediated osteoblastic transition. Furthermore, immunohistochemistry of aorta from the klothoaging mouse model demonstrated in vivo emergence of osteoblastlike cells expressing RUNX-2 exclusively in the calcified media. We also found that statin and Rho-kinase inhibitor effectively reduced the VSMC calcification by inhibiting Pi-induced apoptosis and potentially enhancing matrix Gla protein expression in the senescent VSMCs. These findings strongly suggest an important role of senescent VSMCs in the pathophysiology of senescence-associated medial calcification, and the inhibition of osteoblastic transition could be a new therapeutic approach for the prevention of senescence-associated medial calcification.runt-related transcription factor-2; statin VASCULAR CALCIFICATION is widespread in patients with coronary artery disease and peripheral artery disease (21) and is closely associated with the incidence of cardiovascular events as well as all-cause mortality (3,27,34). Calcification in the tunica media is often observed in elderly people and is highly correlated with their morbidity and mortality (8).Many recent findings have suggested that vascular calcification is regulated by the machinery similar to bone formation, which is accomplished through the extracellular matrix (ECM) calcification (16,21,34). During the ECM calcification, hydroxyapatite crystals that contain calcium and inorganic phosphate precipitate within the collagen fibrils (32). Many key players in the ECM calcification, such as matrix Gla protein (MGP) and alkaline phosphatase (ALP), have been identified (22,32). Inorganic pyrophosphate, a small molecule made of two phosphate ions, and MGP prevent incorporation of mineral crystals into the collagen fibrils ...

The Wnt/beta‐catenin pathway is activated during advanced arterial aging in humans

“…However, we did not see in aged human mammary arteries any regulation of RunX2, a key transcription factor in osteoblast differentiation, which participates in the VSMC calcifying process (Gaur et al, 2005;Byon et al, 2008;Speer et al, 2009). Altogether, our observations are in line with recent publications showing that senescent VSMC can transdifferentiate into osteochondrogenic precursors, an early step in vascular calcification (Burton et al, 2009;Nakano-Kurimoto et al, 2009;Speer et al, 2009). …”

The Impact of Different Amounts of Calcium Intake on Bone Mass and Arterial Calcification in Ovariectomized Rats

“…They also play an active role in bone-like mineralization in the medial elastic site, which leads to loss of elasticity of artery (12,13). Therefore, the osteoblast-like phenotype of the aorta could be positively correlated with the arterial Ca deposition and lead to arterial calcification (16,17,22). Although both the 0.01% and 2.4% Ca intakes are outside the range of normal rodent Ca intake, our data suggest that the Ca metabolism of vascular tissue was altered by the different amounts of calcium intake.…”

“…However, they also play an active role in bone-like mineralization of the media through their osteoblast-like Ca uptake into vessel walls by the process of calcification (12,13). Although the expression of an osteoblast-like phenotype by VSMCs due to this calcification process was previously reported in several in vitro studies (14)(15)(16)(17), to the best of our knowledge, there have been no in vivo studies for the effects of different amounts of Ca intake on an aortic phenotype, such as mRNA expression related to vascular bone-like mineralization.…”

Parathyroid hormone promotes osteoblastic differentiation of endothelial cells via the extracellular signal‑regulated protein kinase 1/2 and nuclear factor‑κB signaling pathways

“…However, previous findings have indicated that VC may be a pathobiological process with respect to embryonic bone formation. It has been demonstrated in animal models that VC may be induced by stimulating various genes, including bone morphogenetic protein (BMP)2, BMP4 (2,3), runt-related transcription factor (RUNX)2 and alkaline phosphatase (ALP) (4). Previous studies have revealed that BMP2 and BMP4, members of the transforming growth factor-b cytokine superfamily, participate in vascular calcification (5).…”