Objective: Although cellular heterogeneity within arterial walls has been explored in mice and nonhuman primates, the cellular composition of human arterial walls remains unclear. Approach and Results: The cellular composition of nondiseased cardiac arteries (3 aortas, 2 pulmonary arteries and 9 coronary arteries) from 3 heart transplantation patients were investigated by single-cell sequencing of >10 5 cells. Clustering analysis identified 25 subpopulations representing the 10 main arterial cell types: vascular smooth muscle cell (4 clusters), fibroblast (4 clusters), macrophage (Mφ, 4 clusters), T cell (4 clusters), endothelial cell (4 clusters), NK cell (2 clusters), mast cell (1 cluster), myofibroblast (1 cluster), oligodendrocyte (1 cluster), and B/plasma cells (1 cluster). Vascular smooth muscle cell was the largest cell population in cardiac arteries, followed by fibroblast, Mφ, T cell, endothelial cell, NK cell, and so on. We compared cellular composition among different arteries and found some artery-specific vascular smooth muscle cell and fibroblast subpopulations. The communication between vascular smooth muscle cell and fibroblast was predominant in nondiseased condition. Atherosclerosis-associated genes were particularly enriched in endothelial cell and Mφ, and intercellular communication between endothelial cell and immune cells was predicted to increase in atherosclerosis. The interaction between ICAM1 / VCAM1 (EC1) and ITGB2 (immune cells, especially inflammatory Mφ) was speculated to be essential for the pathogenesis of atherosclerosis. Conclusions: We created a cell atlas of human nondiseased cardiac arteries, and characterized the cellular compositions in different cardiac arteries. Our results could be used as a reference to identify vascular disease-associated cell populations and help investigate new therapeutic strategies for vascular diseases.

Removal of the IP receptors unmasks a protective role of mPGES-1-derived PGE in limiting injury-induced vascular hyperplasia. EP4, in the endothelial compartment, is essential to promote reendothelialization and restrain neointimal formation after injury. Activating EP4 bears therapeutic potential to prevent restenosis after percutaneous coronary intervention.

Human umbilical cord blood derived mesenchymal stem cells (uMSC) are pluripotent cells that have been now considered as a promising candidate for various cell-based therapies. However, their limited in vitro proliferation ability and the gradual loss of pluripotency set barricades for further usages. Emerging evidence suggests that small nucleolar RNAs (snoRNA) are actively involved in cell proliferation especially in tumor cells, but their roles in stem cells are largely unknown. In this study, we demonstrated that H/ACA box small nucleolar RNA 7A (SNORA7A) is inversely correlated to the decreased proliferation rate during in vitro passaging of uMSC. Further investigations indicate that SNORA7A overexpression can promote uMSC proliferation and self-renewal. The inhibition of SNORA7A using antisense oligonucleotides significantly reduces the expression and the binding of SNORA7A to DKC1, core protein that essential to form small nucleolar ribonucleo-particles (snoRNP) complex and catalyze pseudouridines in 28S RNA. And the inhibition also significantly suppresses uMSC proliferation and self-renewal. Moreover, overexpression of SNORA7A transcripts with mutations of binding regions for snoRNP core proteins and 28S RNA did not induce proliferation and self-renewal. Besides, SNORA7A also suppresses both the osteogenic and adipogenic differentiation, strengthening its self-renewal maintaining roles in uMSC. Taken together, our study for the first time showed that H/ACA box snoRNAs are actively involved in MSC proliferation as well as pluripotency control, and we identify SNORA7A as one of the critical snoRNAs that regulate the proliferation and self-renewal of uMSC through snoRNP recruiting. STEM CELLS 2017;35:222-235 SIGNIFICANCE STATEMENTThe endogenous H/ACA box small nucleolar RNA 7A is critical for the proliferation of human umbilical cord mesemchymal stem cells through recuiting small nucleolar ribonucleo-particles. This finding may increase our understanding for the regulation network of stem cell biology, and may have the further implications in stem cells clinical applications.

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Neointimal formation and atherogenesis are major vascular complications following percutaneous coronary intervention, and there is lack of pharmacological therapy. This study was aimed to examine the effect of forskolin (FSK), a cyclic adenosine monophosphate (cAMP)‐elevating agent, on vascular response to angioplasty wire injury and on atherogenesis in mice. Forskolin treatment reduced neointima formation at 7 and 28 days after wire injury. Early morphometrics of the injured vessels revealed that FSK treatment enhanced endothelial repair and reduced inflammatory cell infiltration. In vitro treatment of primary aortic cells with FSK, at 3‐100 μmol/L, increased endothelial cell proliferation, whereas FSK, at 30‐100 μmol/L, inhibited smooth muscle cell proliferation. FSK inhibited lipopolysaccharide‐induced leucocyte‐endothelial interaction in vitro and in vivo. In a mouse model of atherosclerosis driven by dyslipidaemia and hypertension, FSK administration increased endothelial repair and reduced atherosclerotic plaque formation, without affecting blood pressure, plasma lipids or aortic aneurysms formation. In summary, FSK, at doses relevant to human therapeutic use, protects against neointimal hyperplasia and atherogenesis, and this is attributable to its activities on pro‐endothelial repair and anti‐inflammation. This study raises a potential of clinical use of FSK as an adjunct therapy to prevent restenosis and atherosclerosis after percutaneous coronary intervention.