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Lyso-phosphatidylcholine induces osteogenic gene expression and phenotype in vascular smooth muscle cells.

ABSTRACT: Calcifying vascular cells in human atherosclerotic plaques actively contribute to ectopic vascular mineralization. Lyso-phosphatidylcholine (LPC), a product of oxidized phosphatidylcholine hydrolysis, is found at concentrations of 1-12 microg/g tissue throughout the atheroma. The objective of this study was to determine if LPC induces an osteogenic phenotype in vascular smooth muscle cells.Proliferating human aortic smooth muscle cells were treated with a wide-range of LPC concentrations (0.1 nM to 100 microM) over 14 days. Von Kossa, Alizarin Red S, and alkaline phosphatase staining were used to identify mineralizations. RT-PCR, ELISA, alkaline phosphatase activity, and 45Ca incorporation assays were used to evaluate the osteo-inductive effect of LPC on smooth muscle phenotype. Histology and morphometry revealed that cells treated with as little as 10 nM LPC produced calcium phosphate deposits in culture. LPC-treated vascular smooth muscle cells showed a significant increase in 45Ca incorporation and alkaline phosphatase activity. Furthermore, LPC treatment induced a significant loss of Schnurri 3 protein, a key repressor of Runt-related transcription factor 2 stability. Genomic studies revealed that osteogenic gene expression was significantly up-regulated in LPC-treated cells, which is attributed to increased Runt-related transcription factor 2 expression and transcriptional activity.LPC induces osteogenic morphology, physiology, gene expression, and phenotype in vascular smooth muscle cells. The present study suggests that localized concentrations of LPC in human atherosclerotic plaques may be a contributing factor to the generation of calcifying vascular cells.

SUBMITTER: Vickers KC

PROVIDER: S-EPMC2902706 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Lyso-phosphatidylcholine induces osteogenic gene expression and phenotype in vascular smooth muscle cells.

Vickers Kasey C KC Castro-Chavez Fernando F Morrisett Joel D JD

Atherosclerosis 20100414 1

<h4>Objective</h4>Calcifying vascular cells in human atherosclerotic plaques actively contribute to ectopic vascular mineralization. Lyso-phosphatidylcholine (LPC), a product of oxidized phosphatidylcholine hydrolysis, is found at concentrations of 1-12 microg/g tissue throughout the atheroma. The objective of this study was to determine if LPC induces an osteogenic phenotype in vascular smooth muscle cells.<h4>Methods and results</h4>Proliferating human aortic smooth muscle cells were treated w ...[more]

PMID: 20451909

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Project description:BACKGROUND:In vitro cell culture is a widely used technique for investigating a range of processes such as stem cell behavior, regenerative medicine, tissue engineering, and drug discovery. Conventional cell culture is performed in Petri dishes or flasks where cells typically attach to a flat glass or plastic surface as a cell monolayer. However, 2D cell monolayers do not provide a satisfactory representation of in vivo conditions. A 3D culture could be a much better system for representing the conditions that prevail in vivo. METHODS AND RESULTS:To simulate 3D conditions, vascular smooth muscle cells (VSMCs) were loaded with gold-polyvmer-iron oxide hydrogel, enabling levitation of the cells by using spatially varying magnetic fields. These magnetically levitated 3D cultures appeared as freely suspended, clustered cells which proliferated 3-4 times faster than cells in conventional 2D cultures. When the levitated cells were treated with 10nM lysophosphatidylcholine (LPC), for 3days, cell clusters exhibited translucent extensions/rods 60-80?m wide and 200-250?m long. When 0.5?g/?l Schnurri-3 was added to the culture containing LPC, these extensions were smaller or absent. When excited with 590-650nm light, these extensions emitted intrinsic fluorescence at >667nm. When the 3D cultures were treated with a fluorescent probe specific for calcium hydroxyapatite (FITC-HABP-19), the cell extensions/rods emitted intensely at 518nm, the ?max for FITC emission. Pellets of cells treated with LPC were more enriched in calcium, phosphate, and glycosaminoglycans than cells treated with LPC and Schnurri-3. CONCLUSIONS:In 3D cultures, VSMCs grow more rapidly and form larger calcification clusters than cells in 2D cultures. Transdifferentiation of VSMC into calcifying vascular cells is enhanced by LPC and attenuated by Schnurri-3. GENERAL SIGNIFICANCE:The formation of calcified structures in 3D VSMC cultures suggests that similar structures may be formed in vivo.

Project description:RationaleVascular calcification is a prominent feature of late-stage diabetes, renal and cardiovascular disease (CVD), and has been linked to adverse events. Recent studies in patients reported that plasma levels of osteomodulin (OMD), a proteoglycan involved in bone mineralisation, associate with diabetes and CVD. We hypothesised that OMD could be implicated in these diseases via vascular calcification as a common underlying factor and aimed to investigate its role in this context.Methods and resultsIn patients with chronic kidney disease, plasma OMD levels correlated with markers of inflammation and bone turnover, with the protein present in calcified arterial media. Plasma OMD also associated with cardiac calcification and the protein was detected in calcified valve leaflets by immunohistochemistry. In patients with carotid atherosclerosis, circulating OMD was increased in association with plaque calcification as assessed by computed tomography. Transcriptomic and proteomic data showed that OMD was upregulated in atherosclerotic compared to control arteries, particularly in calcified plaques, where OMD expression correlated positively with markers of smooth muscle cells (SMCs), osteoblasts and glycoproteins. Immunostaining confirmed that OMD was abundantly present in calcified plaques, localised to extracellular matrix and regions rich in α-SMA+ cells. In vivo, OMD was enriched in SMCs around calcified nodules in aortic media of nephrectomised rats and in plaques from ApoE-/- mice on warfarin. In vitro experiments revealed that OMD mRNA was upregulated in SMCs stimulated with IFNγ, BMP2, TGFβ1, phosphate and β-glycerophosphate, and by administration of recombinant human OMD protein (rhOMD). Mechanistically, addition of rhOMD repressed the calcification process of SMCs treated with phosphate by maintaining their contractile phenotype along with enriched matrix organisation, thereby attenuating SMC osteoblastic transformation. Mechanistically, the role of OMD is exerted likely through its link with SMAD3 and TGFB1 signalling, and interplay with BMP2 in vascular tissues.ConclusionWe report a consistent association of both circulating and tissue OMD levels with cardiovascular calcification, highlighting the potential of OMD as a clinical biomarker. OMD was localised in medial and intimal α-SMA+ regions of calcified cardiovascular tissues, induced by pro-inflammatory and pro-osteogenic stimuli, while the presence of OMD in extracellular environment attenuated SMC calcification.

Project description:ObjectiveWe examined the role of syndecan-1 in modulating the phenotype of vascular smooth muscle cells in the context of endogenous inflammatory factors and altered microenvironments that occur in disease or injury-induced vascular remodeling.Methods and resultsVascular smooth muscle cells (vSMCs) display a continuum of phenotypes that can be altered during vascular remodeling. While the syndecans have emerged as powerful and complex regulators of cell function, their role in controlling vSMC phenotype is unknown. Here, we isolated vSMCs from wild type (WT) and syndecan-1 knockout (S1KO) mice. Gene expression and western blotting studies indicated decreased levels of α-smooth muscle actin (α-SMA), calponin, and other vSMC-specific differentiation markers in S1KO relative to WT cells. The spread area of the S1KO cells was found to be greater than WT cells, with a corresponding increase in focal adhesion formation, Src phosphorylation, and alterations in actin cytoskeletal arrangement. In addition, S1KO led to increased S6RP phosphorylation and decreased AKT and PKC-α phosphorylation. To examine whether these changes were present in vivo, isolated aortae from aged WT and S1KO mice were stained for calponin. Consistent with our in-vitro findings, the WT mice aortae stained higher for calponin relative to S1KO. When exposed to the inflammatory cytokine TNF-α, WT vSMCs had an 80% reduction in syndecan-1 expression. Further, with TNF-α, S1KO vSMCs produced increased pro-inflammatory cytokines relative to WT. Finally, inhibition of interactions between syndecan-1 and integrins αvβ3 and αvβ5 using the inhibitory peptide synstatin appeared to have similar effects on vSMCs as knocking out syndecan-1, with decreased expression of vSMC differentiation markers and increased expression of inflammatory cytokines, receptors, and osteopontin.ConclusionsTaken together, our results support that syndecan-1 promotes vSMC differentiation and quiescence. Thus, the presence of syndecan-1 would have a protective effect against vSMC dedifferentiation and this activity is linked to interactions with integrins αvβ3 and αvβ5.

Project description:RationaleThe phenotypes of vascular smooth muscle cells (vSMCs) comprise a continuum bounded by predominantly contractile and synthetic cells. Some evidence suggests that contractile vSMCs can assume a more synthetic phenotype in response to ischemic injury, but the mechanisms that activate this phenotypic switch are poorly understood.ObjectiveTo determine whether lactate, which increases in response to regional ischemia, may promote the synthetic phenotype in vSMCs.Methods and resultsExperiments were performed with vSMCs that had been differentiated from human induced pluripotent stem cells and then cultured in glucose-free, lactate-enriched (L+) medium or in standard (L-) medium. Compared with the L- medium, the L+ medium was associated with significant increases in synthetic vSMC marker expression, proliferation, and migration and with significant declines in contractile and apoptotic activity. Furthermore, these changes were accompanied by increases in the expression of monocarboxylic acid transporters and were generally attenuated both by the blockade of monocarboxylic acid transporter activity and by transfection with iRNA for NDRG (N-myc downstream regulated gene). Proteomics, biomarker, and pathway analyses suggested that the L+ medium tended to upregulate the expression of synthetic vSMC markers, the production of extracellular proteins that participate in tissue construction or repair, and the activity of pathways that regulate cell proliferation and migration. Observations in hypoxia-cultured vSMCs were similar to those in L+-cultured vSMCs, and assessments in a swine myocardial infarction model suggested that measurements of lactate levels, lactate-dehydrogenase levels, vSMC proliferation, and monocarboxylic acid transporter and NDRG expression were greater in the ischemic zone than in nonischemic tissues.ConclusionsThese results demonstrate for the first time that vSMCs assume a more synthetic phenotype in a microenvironment that is rich in lactate. Thus, mechanisms that link glucose metabolism to vSMC phenotypic switching could play a role in the pathogenesis and treatment of cardiovascular disease.

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Lyso-phosphatidylcholine induces osteogenic gene expression and phenotype in vascular smooth muscle cells.

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Lyso-phosphatidylcholine induces osteogenic gene expression and phenotype in vascular smooth muscle cells.

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