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Abstract The adult mammalian heart has extremely limited cardiac regenerative capacity. Most cardiomyocytes live in a state of permanent cell-cycle arrest and are unable to re-enter the cycle. Cardiomyocytes switch from cell proliferation to a maturation state during neonatal development. Although several signaling pathways are involved in this transition, the molecular mechanisms by which these inputs coordinately regulate cardiomyocyte maturation are not fully understood. Retinoic acid (RA) plays a pivotal role in development, morphogenesis, and regeneration. Despite the importance of RA signaling in embryo heart development, little is known about its function in the early postnatal period. We found that mRNA expression of aldehyde dehydrogenase 1 family member A2 (Aldh1a2), which encodes the key enzyme for synthesizing all-trans retinoic acid (ATRA) and is an important regulator for RA signaling, was transiently upregulated in neonatal mouse ventricles. Single-cell transcriptome analysis and immunohistochemistry revealed that Aldh1a2 expression was enriched in cardiac fibroblasts during the early postnatal period. Administration of ATRA inhibited cardiomyocyte proliferation in cultured neonatal rat cardiomyocytes and human cardiomyocytes. RNA-seq analysis indicated that cell proliferation-related genes were downregulated in prenatal rat ventricular cardiomyocytes treated with ATRA, while cardiomyocyte maturation-related genes were upregulated. These findings suggest that RA signaling derived from cardiac fibroblasts is one of the key regulators of cardiomyocyte proliferation and maturation during neonatal heart development.

Abstract Emerging evidence has documented that circadian rhythm disorders could be related to cardiovascular diseases. However, there is limited knowledge on the direct adverse effects of circadian misalignment on the heart. This study aimed to investigate the effect of chronic circadian rhythm disorder on heart homeostasis in a mouse model of consistent jetlag. The jetlag model was induced in mice by a serial 8-h phase advance of the light cycle using a light-controlled isolation box every 4 days for up to 3 months. Herein, we demonstrated for the first time that chronic circadian rhythm disorder established in the mouse jetlag model could lead to HFpEF-like phenotype such as cardiac hypertrophy, cardiac fibrosis, and cardiac diastolic dysfunction, following the attenuation of the Clock-sGC-cGMP-PKG1 signaling. In addition, clock gene knock down in cardiomyocytes induced hypertrophy via decreased sGC-cGMP-PKG signaling pathway. Furthermore, treatment with an sGC-activator riociguat directly attenuated the adverse effects of jetlag model-induced cardiac hypertrophy, cardiac fibrosis, and cardiac diastolic dysfunction. Our data suggest that circadian rhythm disruption could induce HFpEF-like phenotype through downregulation of the clock-sGC-cGMP-PKG1 signaling pathway. sGC could be one of the molecular targets against circadian rhythm disorder-related heart disease.

Background Accumulating evidence suggests that hydrogen sulfide ( H2S ), 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 H2S 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 H2S 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 H2S 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, H2S donors could be used as therapeutics against refractory secondary lymphedema.

Summary: It is widely accepted that adipose-derived regenerative cells (ADRCs) can differentiate into mesodermal lineage cells. However, reprogramming adult ADRCs into mature cardiomyocytes is challenging. We investigated the induction of myocardial differentiation in ADRCs via direct reprogramming using lentiviral gene transfer. First, we identified candidate transcriptional factors by performing RNA sequencing and ultimately confirmed that the combination of six unique factors (Baf60c, Gata4, Gata6, Klf15, Mef2a, and Myocd) could efficiently express enhanced green fluorescent protein (GFP) in ADRCs isolated from adult alpha-myosin heavy chain promoter-driven GFP transgenic mice. The GFP-positive ADRCs induced by six factors (6F-ADRCs) expressed multiple cardiac genes and revealed cardiac differentiation in bioinformatic analysis. Moreover, injection of 6F-ADRCs into acute myocardial infarcted tissues in vivo resulted in the improvement of survival rate, fractional shortening, and reduction of infarction scar area. This study provides an alternative method for direct reprogramming of adult ADRCs into cardiomyocytes.

The patient was a 62-year-old man with atrial fibrillation and severe scoliosis. Scoliosis may impair cardiorespiratory function. Enhanced computed tomography (CT) was helpful for the Brockenbrough method. Three-dimensional (3D) mapping also demonstrated clockwise rotation of the heart. We successfully isolated extensive encircling pulmonary vein in this patient using enhanced CT and 3D mapping. The CT venous images revealed appropriate localization of the vein and heart. CT and 3D mapping may ensure a more stable and safer procedure.

Therapeutic angiogenesis with autologous stem/progenitor cells is a promising novel strategy for treatment of severe ischemic diseases. Human clinical trials utilizing autologous adipose-derived regenerative cells (ADRCs) have not reported treatmentrelated critical adverse effects thus far. However, there is still a large knowledge gap regarding whether treatment of ischemic diseases with angiogenic therapy using ADRCs would promote unfavorable angiogenesis associated with tumors in vivo. Herein, we addressed this clinical question using a mouse hindlimb ischemia (HLI) and simultaneous remote tumor implantation model. C57BL/6J background wild-type mice were injected with murine B16F10 melanoma cells on their back, 1 day before ischemic surgery. These mice were subjected to surgical unilateral hindlimb ischemia, followed by ADRC implantation or PBS injection into the hindlimb ischemic muscles on the next day. Intramuscular implantation of ADRCs enhanced tissue capillary density and blood flow examined by a laser Doppler blood perfusion analysis in hind limb. However, this therapeutic regimen for ischemic limb using ADRCs did not affect remote melanoma growth nor the density of its feeder artery, angiogenesis, and lymphatic vessels compared with the PBS group. In addition, no distant metastases were detected in any of the mice regardless of the group. In conclusion, local implantation of ADRCs promotes angiogenesis in response to tissue ischemia in the hindlimb without promoting remote tumor growth and related angio/lymphangiogenesis. Therapeutic angiogenesis to the ischemic hindlimb using ADRCs seems to be safe regarding remote tumor growth. NEW & NOTEWORTHY In this study, we demonstrated that local injection of ADRCs can promote angiogenesis in response to tissue ischemia without promoting remote tumor growth in a mouse model. Our findings indicate that therapeutic angiogenesis to the ischemic hindlimb using ADRCs seems to be safe regarding remote tumor growth. [ABSTRACT FROM AUTHOR]