Rationale: Effective neovascularization is crucial for recovery after cardiovascular events. Objective: Because microRNAs regulate expression of up to several hundred target genes, we set out to identify microRNAs that target genes in all pathways of the multifactorial neovascularization process. Using www.targetscan. org, we performed a reverse target prediction analysis on a set of 197 genes involved in neovascularization. We found enrichment of binding sites for 27 microRNAs in a single microRNA gene cluster. Microarray analyses showed upregulation of 14q32 microRNAs during neovascularization in mice after single femoral artery ligation. Methods and Results:Gene silencing oligonucleotides (GSOs) were used to inhibit 4 14q32 microRNAs, miR-329, miR-487b, miR-494, and miR-495, 1 day before double femoral artery ligation. Blood flow recovery was followed by laser Doppler perfusion imaging. All 4 GSOs clearly improved blood flow recovery after ischemia. Mice treated with GSO-495 or GSO-329 showed increased perfusion already after 3 days (30% perfusion versus 15% in control), and those treated with GSO-329 showed a full recovery of perfusion after 7 days (versus 60% in control). Increased collateral artery diameters (arteriogenesis) were observed in adductor muscles of GSO-treated mice, as well as increased capillary densities (angiogenesis) in the ischemic soleus muscle. In vitro, treatment with GSOs led to increased sprout formation and increased arterial endothelial cell proliferation, as well as to increased arterial myofibroblast proliferation. Conclusions Welten et al 14q32 MicroRNAs in Neovascularization 697Both arteriogenesis and angiogenesis are highly multifactorial processes, and yet clinical trials aiming to induce neovascularization in patients with occlusive arterial disease have so far only focused on single-factor therapeutics, such as growth factors (eg, vascular endothelial growth factor A [VEGFA] and basic fibroblast growth factor [bFGF]). Unfortunately, these trials were less successful than anticipated.1,3,4 Growth factors only target 1 of multiple processes required for efficient neovascularization. Therefore, there is a need for novel proarteriogenic and proangiogenic factors that can act as master switches in neovascularization.MicroRNAs are endogenous RNA molecules that downregulate expression of their target genes.5 MicroRNAs do not completely silence their target genes, but rather downtune their expression. However, because each microRNA has multiple, up to several hundred, target genes, changes in microR-NA expression can have a major impact. Inhibition of a single microRNA can thus lead to activation of entire multifactorial physiological processes.Several studies have been published on the effects of microRNA inhibition on neovascularization, but in general, the focus of these studies lies with angiogenesis alone, not arteriogenesis. [6][7][8][9][10][11][12][13][14] In the present study, we exploited the master switch character of microRNAs to identify microRNAs that play a regulat...

Vascular remodelling is a multifactorial process that involves both adaptive and maladaptive changes of the vessel wall through, among others, cell proliferation and migration, but also apoptosis and necrosis of the various cell types in the vessel wall. Vascular remodelling can be beneficial, e.g. during neovascularization after ischaemia, as well as pathological, e.g. during atherosclerosis and aneurysm formation. In recent years, it has become clear that microRNAs are able to target many genes that are involved in vascular remodelling processes and either can promote or inhibit structural changes of the vessel wall. Since many different processes of vascular remodelling are regulated by similar mechanisms and factors, both positive and negative vascular remodelling can be affected by the same microRNAs. A large number of microRNAs has been linked to various aspects of vascular remodelling and indeed, several of these microRNAs regulate multiple vascular remodelling processes, including both the adaptive processes angiogenesis and arteriogenesis as well as maladaptive processes of atherosclerosis, restenosis and aneurysm formation. Here, we discuss the multifactorial role of microRNAs and microRNA clusters that were reported to play a role in multiple forms of vascular remodelling and are clearly linked to cardiovascular disease (CVD). The microRNAs reviewed are miR-126, miR-155 and the microRNA gene clusters 17-92, 23/24/27, 143/145 and 14q32. Understanding the contribution of these microRNAs to the entire spectrum of vascular remodelling processes is important, especially as these microRNAs may have great potential as therapeutic targets for treatment of various CVDs.

Objective-Therapeutic arteriogenesis, that is, expansive remodeling of preexisting collaterals, using single-action factor therapies has not been as successful as anticipated. Modulation of factors that act as a master switch for relevant gene programs may prove more effective. Transcriptional coactivator p300-CBP-associated factor (PCAF) has histone acetylating activity and promotes transcription of multiple inflammatory genes. Because arteriogenesis is an inflammationdriven process, we hypothesized that PCAF acts as multifactorial regulator of arteriogenesis. Approach and Results-After induction of hindlimb ischemia, blood flow recovery was impaired in both PCAF −/− mice and healthy wild-type mice treated with the pharmacological PCAF inhibitor Garcinol, demonstrating an important role for PCAF in arteriogenesis. PCAF deficiency reduced the in vitro inflammatory response in leukocytes and vascular cells involved in arteriogenesis. In vivo gene expression profiling revealed that PCAF deficiency results in differential expression of 3505 genes during arteriogenesis and, more specifically, in impaired induction of multiple proinflammatory genes. Additionally, recruitment from the bone marrow of inflammatory cells, in particular proinflammatory Ly6C Bastiaansen et al PCAF Regulates Arteriogenesis 1903growth are multifactorial and too complex to be modulated by therapeutics that target a single gene or pathway. In contrast, modulation of a factor that acts as a master switch for multiple relevant gene programs may be a more effective strategy to augment arteriogenesis.A protein with such master switch potential is p300-CBPassociated factor (PCAF), a transcriptional coactivator with intrinsic histone acetyltransferase activity. PCAF acetylates histones H3 and H4, but there is also increasing evidence that PCAF modulates nonhistone proteins, [13][14][15][16] including hypoxiainducible factor 1α 17 and Notch. 18 Furthermore, the histone acetylating activity of PCAF is essential for nuclear factor κB (NF-κB)-mediated gene transcription 19 and facilitates inflammatory gene regulation. 20 Because arteriogenesis is an inflammatory-like process, we hypothesized that PCAF acts as master switch that stimulates multiple inflammatory processes important for collateral remodeling.Recently, it was shown in a large patient population study (>3000 individuals)21 that a variation in the promoter region of PCAF is associated with coronary heart disease-related mortality. 22 In support of this observation, we recently demonstrated a role for PCAF in vascular remodeling in a mouse model for reactive stenosis. However, whether PCAF participates in arteriogenesis has not yet been investigated.In the present study, we investigated the contribution of PCAF to postischemic neovascularization in a hindlimb ischemia (HLI) model, 23 using PCAF-deficient (PCAF −/− ) mice. When studying arteriogenesis in a knockout model, it is possible that the gene deletion may affect vascular development in the embryo, including collaterogenesis, thus affec...

BackgroundIn order to identify factors that stimulate arteriogenesis after ischemia, we followed gene expression profiles in two extreme models for collateral artery formation over 28 days after hindlimb ischemia, namely “good‐responding” C57BL/6 mice and “poor‐responding” BALB/c mice.Methods and ResultsAlthough BALB/c mice show very poor blood flow recovery after ischemia, most known proarteriogenic genes were upregulated more excessively and for a longer period than in C57BL/6 mice. In clear contrast, chemokine genes Ccl19, Ccl21a, and Ccl21c and the chemokine receptor CCR7 were upregulated in C57BL/6 mice 1 day after hindlimb ischemia, but not in BALB/C mice. CCL19 and CCL21 regulate migration and homing of T lymphocytes via CCR7. When subjecting CCR7−/−/LDLR −/− mice to hindlimb ischemia, we observed a 20% reduction in blood flow recovery compared with that in LDLR −/− mice. Equal numbers of α‐smooth muscle actin–positive collateral arteries were found in the adductor muscles of both mouse strains, but collateral diameters were smaller in the CCR7−/−/LDLR −/−. Fluorescence‐activated cell sorter analyses showed that numbers of CCR7+ T lymphocytes (both CD4+ and CD8+) were decreased in the spleen and increased in the blood at day 1 after hindlimb ischemia in LDLR −/− mice. At day 1 after hindlimb ischemia, however, numbers of activated CD4+ T lymphocytes were decreased in the draining lymph nodes of LDLR −/− mice compared with CCR7−/−/LDLR −/− mice.ConclusionsThese data show that CCR7‐CCL19/CCL21 axis facilitates retention CD4+ T lymphocytes at the site of collateral artery remodeling, which is essential for effective arteriogenesis.

Treatment with GSO-494 results in smaller atherosclerotic lesions with increased plaque stability. Inhibition of miR-494 may decrease the risk of surgical complications or even avert endarterectomy surgery in some cases.

AimsWe investigated the role of the TLR4-accessory molecule RP105 (CD180) in post-ischemic neovascularization, i.e. arteriogenesis and angiogenesis. TLR4-mediated activation of pro-inflammatory Ly6Chi monocytes is crucial for effective neovascularization. Immunohistochemical analyses revealed that RP105+ monocytes are present in the perivascular space of remodeling collateral arterioles. As RP105 inhibits TLR4 signaling, we hypothesized that RP105 deficiency would lead to an unrestrained TLR4-mediated inflammatory response and hence to enhanced blood flow recovery after ischemia.Methods and ResultsRP105−/− and wild type (WT) mice were subjected to hind limb ischemia and blood flow recovery was followed by Laser Doppler Perfusion Imaging. Surprisingly, we found that blood flow recovery was severely impaired in RP105−/− mice. Immunohistochemistry showed that arteriogenesis was reduced in these mice compared to the WT. However, both in vivo and ex vivo analyses showed that circulatory pro-arteriogenic Ly6Chi monocytes were more readily activated in RP105−/− mice. FACS analyses showed that Ly6Chi monocytes became activated and migrated to the affected muscle tissues in WT mice following induction of hind limb ischemia. Although Ly6Chi monocytes were readily activated in RP105−/− mice, migration into the ischemic tissues was hampered and instead, Ly6Chi monocytes accumulated in their storage compartments, bone marrow and spleen, in RP105−/− mice.ConclusionsRP105 deficiency results in an unrestrained inflammatory response and monocyte over-activation, most likely due to the lack of TLR4 regulation. Inappropriate, premature systemic activation of pro-inflammatory Ly6Chi monocytes results in reduced infiltration of Ly6Chi monocytes in ischemic tissues and in impaired blood flow recovery.

GSO-495 administration decreased our primary outcomes, namely intimal hyperplasia, and accelerated atherosclerosis. GSO-495 administration also favourably affected multiple secondary outcomes, including macrophage influx, plaque stability and total plasma cholesterol levels. We conclude that 14q32 microRNA miR-495 is a promising target for prevention of restenosis.

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