Rationale: Endothelial cells (EC) play a critical role in multiple cardiovascular diseases. Circulating CD34+ cells are believed to be endothelial progenitors that have been used to treat cardiovascular diseases. However, the exact identity and the role of CD34+ cells in vascular regeneration remains unclear. Objective: We aimed to investigate the exact identity and the role of CD34+ cells in vascular regeneration. Methods and Results: Compared to healthy arteries, CD34 expression percentage was significantly increased in diseased femoral arteries from patients. Using a guide-wire induced endothelial denudation model, we reported the transcriptional profiling of over 30,000 cells by single-cell RNA sequencing analysis and provided a cell atlas of normal and lesioned arteries in mouse, in which a heterogeneous population of CD34+ cells were revealed. Combining the inducible lineage tracing Cd34-CreERT2;R26-tdTomato mouse model and bone marrow transplantation experiments, we showed that nonbone marrow CD34+ mesenchymal cells acquired endothelial cell fate in the injured femoral artery rather than pre-exiting ECs, while bone marrow-derived CD34+ cells differentiated into immune cells locally after vessel injury. Depletion of nonbone marrow CD34+ cells using diphtheria toxin induced cell ablation models, exacerbate neointimal lesions of the injured vessel. Furthermore, isolated vascular adventitia CD34+ cells displayed endothelial differentiation, in which microRNA-21-Smad7-pSmad2/3 pathway regulated endothelial gene expression and function during differentiation. Conclusions: Our study provides a transcriptional and cellular landscape of vessels after endothelial denudation. Our findings suggest heterogeneous CD34+ cells serve as a contributor not only to endothelial regeneration but also an inflammatory response that may provide therapeutic insights into vascular diseases.

Background As the most important component of the vascular wall, vascular smooth muscle cells (VSMCs) participate in the pathological process by phenotype transformation or differentiation from stem/progenitor cells. The main purpose of this study was to reveal the role and related molecular mechanism of microRNA-30c-5p (miR-30c-5p) in VSMC differentiation from adventitial progenitor cells expressing stem cell antigen-1(Sca-1). Methods In this study, we detected the expression of miR-30c-5p in human normal peripheral arteries and atherosclerotic arteries. In vitro, a stable differentiation model from adventitial Sca-1+ progenitor cells to VSMCs was established using transforming growth factor-β1 (TGF-β1) induction and the expression of miR-30c-5p during the process was observed. Then, we explored the effect of miR-30c-5p overexpression and inhibition on the differentiation from adventitial Sca-1+ progenitor cells to VSMCs. The target genes of miR-30c-5p were identified by protein chip and biological analyses and the expression of these genes in the differentiation process were detected. Further, the relationship between the target gene and miR-30c-5p and its effect on differentiation were evaluated. Finally, the co-transfection of miR-30c-5p inhibitor and small interfering RNA (siRNA) of the target gene was implemented to verify the functional target gene of miR-30c-5p during the differentiation from adventitial Sca-1+ progenitor cells to VSMCs, and the dual-luciferase reporter gene assay was performed to detect whether the mRNA 3′untranslated region (UTR) of the target gene is the direct binding site of miR-30c-5p. Results The expression of miR-30c-5p in the human atherosclerotic arteries was significantly lower than that in the normal arteries. During the differentiation from adventitial Sca-1+ progenitor cells to VSMCs, the expression of VSMC special markers including smooth muscle α-actin (SMαA), smooth muscle-22α (SM22α), smooth muscle myosin heavy chain (SMMHC), and h1-caponin increased accompanied with cell morphology changing from elliptic to fusiform. Meanwhile, the expression of miR-30c-5p decreased significantly. In functional experiments, overexpression of miR-30c-5p inhibited SMαA, SM22α, SMMHC, and h1-caponin at the mRNA and protein levels. In contrast, inhibition of miR-30c-5p promoted the expression of SMαA, SM22α, SMMHC, and h1-caponin. The target gene, osteoprotegerin (OPG), was predicted through protein chip and bioinformatics analyses. Overexpression of miR-30c-5p inhibited OPG expression while inhibition of miR-30c-5p had an opposite effect. Co-transfection experiments showed that low expression of OPG could weaken the promotion effect of miR-30c-5p inhibitor on the differentiation from adventitial Sca-1+ progenitor cells to VSMCs and the dual-luciferase reporter gene assay demonstrated that miR-30c-5p could target the mRNA 3′UTR of OPG directly. Conclusions This study demonstrates that miR-30c-5p expression was significantly decreased in atherosclerotic arteries and miR-30c-5p inhibited VSMC differentiation from adventitial Sca-1+ progenitor cells through targeting OPG, which may provide a new target for the treatment of VSMCs-associated diseases.

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Vein graft failure remains a significant clinical problem. Similar to other vascular diseases, stenosis of vein grafts is caused by several cell lines; however, the sources of these cells remain unclear. The objective of this study was to investigate the cellular sources that reshape vein grafts. By analyzing transcriptomics data and constructing inducible lineage-tracing mouse models, we investigated the cellular components of vein grafts and their fates. The sc-RNAseq data suggested that Sca-1+ cells were vital players in vein grafts and might serve as progenitors for multilineage commitment. By generating a vein graft model in which the venae cavae from C57BL/6J wild-type mice were transplanted adjacent to the carotid arteries of Sca-1(Ly6a)-CreERT2; Rosa26-tdTomato mice, we demonstrated that the recipient Sca-1+ cells dominated reendothelialization and the formation of adventitial microvessels, especially at the perianastomotic regions. In turn, using chimeric mouse models, we confirmed that the Sca-1+ cells that participated in reendothelialization and the formation of adventitial microvessels all had a non-bone-marrow origin, whereas bone-marrow-derived Sca-1+ cells differentiated into inflammatory cells in vein grafts. Furthermore, using a parabiosis mouse model, we confirmed that non-bone-marrow-derived circulatory Sca-1+ cells were vital for the formation of adventitial microvessels, whereas Sca-1+ cells derived from local carotid arteries were the source of endothelium restoration. Using another mouse model in which venae cavae from Sca-1 (Ly6a)-CreERT2; Rosa26-tdTomato mice were transplanted adjacent to the carotid arteries of C57BL/6J wild-type mice, we confirmed that the donor Sca-1+ cells were mainly responsible for smooth muscle cells commitment in the neointima, particularly at the middle bodies of vein grafts. In addition, we provided evidence that knockdown/knockout of Pdgfrα in Sca-1+ cells decreased the cell potential to generate SMCs in vitro and decreased number of intimal SMCs in vein grafts. Our findings provided cell atlases of vein grafts, which demonstrated that recipient carotid arteries, donor veins, non-bone-marrow circulation, and the bone marrow provided diverse Sca-1+ cells/progenitors that participated in the reshaping of vein grafts.