Thrombospondin-1 differentially regulates microRNAs in vascular smooth muscle cells.

Thrombospondin-1 (TSP-1) is an important regulator of vascular smooth muscle cell (VSMC) physiology and gene expression. MicroRNAs (microRNA), small molecules that regulate protein translation, have emerged as potent regulators of cell function. MicroRNAs have been shown to be involved in intimal hyperplasia, atherosclerosis, and upregulated in the vasculature in diabetes. The purpose of this study was to identify microRNAs regulated by TSP-1 in vascular smooth muscle cells (VSMCs). Human VSMCs were treated for 6 h with basal media or TSP-1 both supplemented with 0.2% FBS. Cells were then snap frozen and RNA extracted. An Affymetrix GeneChip microRNA array analysis was performed in triplicate on three separate collections. Confirmatory qrtPCR was performed. Data were analyzed by ANOVA or t test, with significance set at p < 0.05. MicroRNAs identified were subjected to KEGG pathway analysis using the DIANA tools miRPath online tool. TSP-1 upregulated 22 microRNAs and downregulated 18 microRNAs in VSMCs (p < 0.05). The most upregulated microRNA was miR-512-3p (45.12 fold). The microRNA most downregulated by TSP-1 was miR-25-5p, which was decreased by 9.61. Of note, five members of the mir-17-92 cluster were downregulated. KEGG analysis revealed that thirty-three cellular signaling pathways were impacted by these microRNAs and that nine pathways were relevant to vascular disease. MicroRNAs regulate protein expression at the level of translation and may represent a significant mechanism by which TSP-1 regulates VSMC function. Several of the microRNAs identified have a role in vascular function. The miR-17-92 cluster family, which was found to exhibit reduced expression in this study, is known to be involved in angiogenesis and vascular function. TSP-1 regulates multiple microRNAs in VSMCs adding a new layer of complexity to TSP-1 regulation of VSMC function.

Dyslipidemia regulates thrombospondin-1-induced vascular smooth muscle cell chemotaxis.

UNLABELLED: Dyslipidemia is a risk factor for intimal hyperplasia (IH). Key to IH is vascular smooth muscle cell (VSMC) migration. Thrombospondin-1 (TSP-1) is a matricellular protein that stimulates VSMC migration. HYPOTHESIS: HDL will inhibit and LDL will augment TSP-1-induced VSMC chemotaxis. VSMC chemotaxis will be inhibited by the HDL moiety, S1P, through the S1PR1 receptor, and augmented by the LDL component, LPA, through the LPAR1 receptor. The goal of this study was to determine the effect of HDL and LDL and their receptors on TSP-1-induced VSMC chemotaxis. For VSMC chemotaxis to TSP-1 cells received the following pretreatments: low (25 µg/ml) or optimal (75 µg/ml) concentration of HDL, S1P, optimal (75 µg/ml) or high (175 µg/ml) concentration of LDL, or LPA. For the receptor studies, VSMCs were transfected with siRNA to S1PR1, S1PR3, LPAR1, LPAR2, LPAR3, or a S1PR2 receptor antagonist. The TSP-1-induced chemotaxis results were (1) HDL (25 µg/ml) or LDL (75 µg/ml) exhibited no effect on chemotaxis; (2) HDL (75 µg/ml) inhibited chemotaxis by 50.9 ± 8 % and S1P by 43.4 ± 11.6 %; (3) LDL (175 µg/ml) augmented chemotaxis by 30 ± 10.4 % and LPA by 25.6 ± 12.3 %; (4) S1PR1 and S1PR3 knockdown and S1PR2 antagonist-treated cells augmented chemotaxis; and (5) LPAR1 and LPAR2 knockdown inhibited and LPAR3 knockdown had no effect on chemotaxis. In conclusion, HDL/S1P inhibits, while LDL/LPA stimulates TSP-1-induced VSMC chemotaxis. The HDL/S1P effect is mediated by the S1PR1-3 receptors. The LDL/LPA effects are mediated by the LPAR1 and LPAR2 receptors, but not LPAR3. Therefore, lipids have significant effects on TSP-1-induced VSMC chemotaxis.

Thrombospondin-1-induced vascular smooth muscle cell migration and proliferation are functionally dependent on microRNA-21.

OBJECTIVES: Thrombospondin-1 (TSP-1) is a matricellular glycoprotein released from platelets at sites of arterial injury and is important in neointima development after balloon angioplasty. MicroRNAs are small noncoding RNAs that function by binding target gene mRNA and inhibiting protein translation. MicroRNA-21 (miR-21) is up-regulated after angioplasty, and inhibition of miR-21 leads to decreased intimal hyperplasia. In this study, we examined the effects of miR-21 inhibition on vascular smooth muscle cell (VSMC) processes. METHODS: VSMCs were exposed to TSP-1 and miR-21 inhibitor for 20 minutes. TSP-1-induced migration was assessed with a modified Boyden microchemotaxis chamber and proliferation with calcein-AM fluorescence. Phosphorylated extracellular signaling kinase (ERK) 1/2 expression was determined by Western Blot and densitometry. Quantitative real-time polymerase chain reaction for TSP-1, hyaluronic acid synthase 2 (HAS2), and transforming growth factor beta 2 (TGFß2) was performed. Statistical analysis was performed with analysis of variance (P < .05). RESULTS: Inhibition of miR-21 blocked TSP-1-induced VSMC migration, proliferation, and ERK 1/2 phosphorylation (P < .05) and had no effect on TSP-1-stimulated expression of genes for TSP-1, HAS2, or TGFß2 (P > .05). CONCLUSION: Acute inhibition of miR-21 led to a decrease in VSMC migration and proliferation caused by TSP-1. The decrease in TSP-1's activation of ERK 1/2 after acute miR-21 inhibition indicates an active role for miR-21 in TSP-1's cell signaling cascade. No effect on TSP-1-induced expression of the pro-stenotic genes thbs1, tgfb2, or has2, occurred after acute miR-21 inhibition. These data indicate that miR-21 directly modulates cell function and signaling pathways in ways other than inhibition of protein translation.

Thrombospondin-1-induced smooth muscle cell chemotaxis and proliferation are dependent on transforming growth factor-ß2 and hyaluronic acid synthase.

Angioplasty causes local vascular injury, leading to the release of thrombospondin-1 (TSP-1), which stimulates vascular smooth muscle cell (VSMC) migration and proliferation, important steps in the development of intimal hyperplasia. Transforming growth factor beta 2 (TGF-ß2) and hyaluronic acid synthase (HAS) are two pro-stenotic genes upregulated in VSMCs by TSP-1. We hypothesized that inhibition of TGF-ß2 or HAS would inhibit TSP-1-induced VSMC migration, proliferation, and TSP-1 signaling. Our data demonstrate that Inhibition of either TGF-ß2 or HAS inhibited TSP-1-induced VSMC migration and proliferation. Activation of ERK 1 was decreased by TGF-ß2 inhibition and unaffected by HAS inhibition. TGF-ß2 and HAS are not implicated in TSP-1-induced thbs1 expression, while they are each implicated in TSP-1-induced expression of their own gene. In summary, TSP-1-induced VSMC migration and proliferation rely on intact TGF-ß2 signaling and HAS function. TSP-1 activation of ERK 1 is dependent on TGF-ß2. These data further expand our understanding of the complexity of TSP-1 cellular signaling and the involvement of TGF-ß2 and HAS.

Bilateral lower extremity acute thromboembolism as first presentation for cancer in a child: an interesting report.

Although it rarely occurs in children, acute arterial thromboembolism can cause significant morbidity and mortality. Rapid diagnosis and prompt treatment can increase the chances of survival with a functional limb. We describe the case of a 10-year-old boy with acute bilateral lower extremity ischemia due to arterial thromboemboli originating from a rare cancer. We discuss diagnosis of and treatment strategies for acute arterial thromboembolism in the pediatric population, as well as the rare cancer the patient was diagnosed with.

Vascular smooth muscle cell migration induced by domains of thrombospondin-1 is differentially regulated.

BACKGROUND: Thrombospondin-1 (TSP-1) stimulates vascular smooth muscle cell (VSMC) migration via defined intracellular signaling pathways. The aim of this study was to examine the signaling pathways whereby TSP-1 folded domains (amino-terminal [NH(2)], procollagen homology [PCH], all 3 type 1 repeats [3TSR], and a single recombinant protein containing the 3rd type 2 repeat, the type 3 repeats, and the carboxyl-terminal [E3T3C1]) induce VSMC migration. METHODS: Quiescent VSMCs were pretreated with serum-free media or inhibitors: PP2 (c-Src), LY294002 (phosphatidylinositol 3-kinase), FPT (Ras), Y27632 (Rho kinase), SB202190 (p38 kinase), and PD98059 (extracellular signal-regulated kinase). Migration induced by serum-free media, TSP-1, NH(2), PCH, 3TSR, and E3T3C1 was assessed using a modified Boyden chamber. RESULTS: TSP-1, NH(2), 3TSR, and E3T3C1 induced VSMC chemotaxis (P < .05), but PCH did not (P > .05). PP2, FPT, SB202190, and PD98059 attenuated chemotaxis stimulated by TSP-1, NH(2), 3TSR, and E3T3C1 (P < .05). LY294002 inhibited TSP-1-induced and E3T3C1-induced (P < .05) but not NH(2)-induced or 3TSR-induced (P > .05) chemotaxis. Y27632 inhibited NH(2)-induced, 3TSR-induced, and E3T3C1-induced (P < .05) but not TSP-1-induced (P > .05) induced chemotaxis. CONCLUSIONS: TSP-1 folded domains are differentially dependent on intracellular signaling pathways to induce migration.

The effects of nicotine on vascular smooth muscle cell chemotaxis induced by thrombospondin-1 and fibronectin.

BACKGROUND: Vascular smooth muscle cell (VSMC) migration is an important process in many vascular disorders. Nicotine, thrombospondin-1 (TSP-1) and fibronectin (Fn) separately induce VSMC migration. The hypothesis of this study was that nicotine treatment of vascular cells would augment TSP-1-induced and Fn-induced VSMC migration. METHODS: VSMCs or endothelial cells (ECs) were treated with serum-free medium or nicotine. Migration of VSMCs was assessed using a modified Boyden chemotaxis chamber to serum-free medium, TSP-1, Fn, EC basal medium, and conditioned EC medium or nicotine-treated conditioned EC medium alone or with supplemented TSP-1 or Fn. RESULTS: Nicotine treatment increased VSMC chemotaxis to serum-free medium, but TSP-1 or Fn had no further effect on chemotaxis. Conditioned EC and nicotine-treated conditioned EC enhanced VSMC chemotaxis, which was further augmented by Fn supplementation. CONCLUSIONS: Nicotine-stimulated EC derived factors induce VSMC migration, which is augmented by the addition of Fn.

External compression of the superior mesenteric artery by the median arcuate ligament.

The median arcuate ligament can compress the proximal portion of the celiac artery causing symptoms of chronic mesenteric ischemia. This rare condition typically affects young women and often poses a diagnostic challenge. Compression of the superior mesenteric artery (SMA) in addition to the celiac artery represents an unusual variant of median arcuate ligament syndrome (MALS). We present a case of MALS resulting predominantly from external compression of the SMA. Diagnostic and therapeutic options are discussed.