Background Circadian rhythm disorders, often seen in modern lifestyles, are a major social health concern. The aim of this study was to examine whether circadian rhythm disorders would influence angiogenesis and blood perfusion recovery in a mouse model of hind limb ischemia. Methods and Results A jet‐lag model was established in C57BL/6J mice using a light‐controlled isolation box. Control mice were kept at a light/dark 12:12 (12‐hour light and 12‐hour dark) condition. Concentrations of plasma vascular endothelial growth factor and circulating endothelial progenitor cells in control mice formed a circadian rhythm, which was diminished in the jet‐lag model ( P <0.05). The jet‐lag condition deteriorated tissue capillary formation ( P <0.001) and tissue blood perfusion recovery ( P <0.01) in hind limb ischemia, which was associated with downregulation of vascular endothelial growth factor expression in local ischemic tissue and in the plasma. Although the expression of clock genes (ie, Clock , Bmal1 , and Cry ) in local tissues was upregulated after ischemic injury, the expression levels of cryptochrome (Cry) 1 and Cry2 were inhibited by the jet‐lag condition. Next, Cry1 and Cry2 double‐knockout mice were examined for blood perfusion recoveries and a reparative angiogenesis. Cry1 and Cry2 double‐knockout mice revealed suppressed capillary density ( P <0.001) and suppressed tissue blood perfusion recovery ( P <0.05) in the hind limb ischemia model. Moreover, knockdown of CRY1/2 in human umbilical vein endothelial cells was accompanied by increased expression of WEE1 and decreased expression of HOXC5 . This was associated with decreased proliferative capacity, migration ability, and tube formation ability of human umbilical vein endothelial cells, respectively, leading to impairment of angiogenesis. Conclusions Our data suggest that circadian rhythm disorder deteriorates reparative ischemia‐induced angiogenesis and that maintenance of circadian rhythm plays an important role in angiogenesis.

Objective: Lymphatic vessels are distributed throughout the body and tightly collaborate with blood vessels to maintain tissue homeostasis. However, the functional roles of lymphangiogenesis in the process of reparative angiogenesis in ischemic tissues are largely unknown. Accordingly, we investigated potential roles of lymphangiogenesis using a mouse model of ischemia-induced angiogenesis. Approach and Results: Male C57BL/6J mice were subjected to unilateral hindlimb ischemia, in which not only angiogenesis but also lymphangiogenesis was induced. Next, the excessive and prolonged tissue edema model significantly deteriorated reparative angiogenesis and blood perfusion recovery in ischemic limbs. Finally, implantation of adipose-derived regenerative cells augmented ischemia-induced lymphangiogenesis, which was accompanied by reduced tissue edema and inflammation, resulting in improving reparative angiogenesis and blood perfusion recovery. In addition, inhibition of lymphangiogenesis by MAZ51, a specific VEGFR3 (vascular endothelial cell growth factor receptor 3) inhibitor, resulted in enhanced inflammatory cell infiltration, gene expression of TNF (tumor necrosis factor)-α, IL (interleukin)-1β, IL-6, TGF (transforming growth factor)-β, angiostatin, vasohibin, and endostatin, and tissue edema, resulting in reduced angiogenesis. Conclusions: The lymphatic system may have a clearance role of tissue edema and inflammation, which contribute to functional reparative angiogenesis in response to tissue ischemia. Modulation of lymphangiogenesis would become a novel therapeutic strategy for severe ischemic disease in addition to ordinary vascular intervention and therapeutic angiogenesis.

MiRNA expression was determined in both proliferating and differentiated cardiac stem cells (CSCs) through a comprehensive miRNA microarray analysis. We selected miR218 for functional follow-up studies to examine its significance in CSCs. First, we observed that the expression of miR218 was altered in CSCs during differentiation into cardiomyocytes, and transfection of an miR218 mimic or miR218 inhibitor affected the myocardial differentiation of CSCs. Furthermore, we observed that a negative regulator of Wnt signaling, sFRP2, was a direct target of miR218, and the protein levels of sFRP2 were increased in cells transfected with the synthetic miR218 inhibitor. In contrast, transfection with the miR218 mimic decreased the expression of sFRP2 and potentiated Wnt signaling. The subsequent down-regulation of sFRP2 by shRNA potentiated Wnt signaling, contributing to a gene expression program that is important for CSC proliferation and cardiac differentiation. Specifically, canonical Wnt signaling induced miR218 transcription. Thus, miR218 and Wnt signaling were coupled through a feed-forward positive feedback loop, forming a biological regulatory circuit. Together, these results provide the first evidence that miR218 plays an important role in CSC proliferation and differentiation through the canonical Wnt signaling pathway.

Background Accumulating evidence suggests that hydrogen sulfide ( H 2 S ), an endogenously produced gaseous molecule, plays a critical role in the regulation of cardiovascular homeostasis. However, little is known about its role in lymphangiogenesis. Thus, the current study aimed to investigate the involvement of H 2 S in lymphatic vessel growth and lymphedema resolution using a murine model and assess the underlying mechanisms. Methods and Results A murine model of tail lymphedema was created both in wild‐type mice and cystathionine γ‐lyase–knockout mice, to evaluate lymphedema up to 28 days after lymphatic ablation. Cystathionine γ‐lyase–knockout mice had greater tail diameters than wild‐type mice, and this phenomenon was associated with the inhibition of reparative lymphangiogenesis at the site of lymphatic ablation. In contrast, the administration of an H 2 S donor, diallyl trisulfide, ameliorated lymphedema by inducing the formation of a considerable number of lymphatic vessels at the injured sites in the tails. In vitro experiments using human lymphatic endothelial cells revealed that diallyl trisulfide promoted their proliferation and differentiation into tube‐like structures by enhancing Akt (protein kinase B) phosphorylation in a concentration‐dependent manner. The blockade of Akt activation negated the diallyl trisulfide–induced prolymphangiogenic responses in lymphatic endothelial cells. Furthermore, the effects of diallyl trisulfide treatment on lymphangiogenesis in the tail lymphedema model were also negated by the inhibition of phosphoinositide 3'‐kinase (P13K)/Akt signaling. Conclusions H 2 S promotes reparative lymphatic vessel growth and ameliorates secondary lymphedema, at least in part, through the activation of the Akt pathway in lymphatic endothelial cells. As such, H 2 S donors could be used as therapeutics against refractory secondary lymphedema.

Plaque rupture followed by intracoronary thrombus formation is recognized as the most common pathophysiological mechanism in acute coronary syndromes (ACS). The second most common underlying substrate for ACS is plaque erosion whose hallmark is thrombus formation without cap disruption. Invasive and non-invasive methods have emerged as a promising tool for evaluation of plaque features that either predict or detect plaque erosion. Optical coherence tomography (OCT), high-definition intravascular ultrasound (IVUS), nearinfrared spectroscopy (NIRS), and near-infrared autofluorescence (NIRF) have been used to study plaque erosion. The detection of plaque erosion in the clinical setting, mainly facilitated by OCT, has shed light upon the complex pathophysiology underlying ACS not related to plaque rupture. Coronary computed tomography angiography (CCTA), which is to date the most commonly used non-invasive technique for coronary plaque evaluation, may also have a role in the evaluation of patients predisposed to erosion. Also, computational models enabling quantification of endothelial shear stress may pave the way to new research in coronary plaque pathophysiology. This review focuses on the recent imaging techniques for the evaluation of plaque erosion including invasive and non-invasive assessment.