Jeffrey J. Stein

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 (TGFβ2) 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 TGFβ2 (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-1s activation of ERK 1/2 after acute miR-21 inhibition indicates an active role for miR-21 in TSP-1s 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.

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.

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.

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.

Statins and Nitric Oxide Donors Affect Thrombospondin 1-Induced Chemotaxis

Background: Thrombospondin 1 (TSP-1) induces vascular smooth muscle cell (VSMC) migration and intimal hyperplasia. Statins and nitric oxide (NO) donors decrease intimal hyperplasia. We previously showed that statins (long-term exposure) and NO donors inhibit TSP-1-induced VSMC chemotaxis. Hypotheses: (1) Pretreatment with short-term statin will inhibit TSP-1-induced VSMC chemotaxis and (2) NO donors will enhance statin inhibition of TSP-1-induced or platelet-derived growth factor (PDGF)-induced VSMC chemotaxis. Methods: We examined these treatment effects on TSP-1-induced VSMC chemotaxis: (1) long-term (20 hours) versus short-term (20 minutes) pravastatin, (2) diethylenetriamine NONOate (DETA/NO) or S-nitroso-N-acetylpenicillamine (SNAP) in combination with pravastatin, and (3) comparison of TSP-1 to PDGF as a chemoattractant. Results: Pravastatin (long term or short term) inhibited TSP-1-induced chemotaxis. Diethylenetriamine NONOate and SNAP impeded statin inhibition of TSP-1-induced chemotaxis. Platelet-derived growth factor and TSP-1 had opposite effects on DETA/NO-pravastatin treatment. Conclusion: Short-term statin pretreatment inhibited TSP-1-induced VSMC chemotaxis, suggesting a pleiotropic effect. High-dose NO reversed statin inhibition of TSP-1-induced chemotaxis, suggesting NO and statin combination therapies warrant further study.

Thrombospondin-1-induced smooth muscle cell chemotaxis and proliferation are dependent on transforming growth factor-β2 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-β2) and hyaluronic acid synthase (HAS) are two pro-stenotic genes upregulated in VSMCs by TSP-1. We hypothesized that inhibition of TGF-β2 or HAS would inhibit TSP-1-induced VSMC migration, proliferation, and TSP-1 signaling. Our data demonstrate that Inhibition of either TGF-β2 or HAS inhibited TSP-1-induced VSMC migration and proliferation. Activation of ERK 1 was decreased by TGF-β2 inhibition and unaffected by HAS inhibition. TGF-β2 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-β2 signaling and HAS function. TSP-1 activation of ERK 1 is dependent on TGF-β2. These data further expand our understanding of the complexity of TSP-1 cellular signaling and the involvement of TGF-β2 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.