The generation of induced pluripotent stem (iPS) cells is an important tool for regenerative medicine. However, the main restriction is the risk of tumor development. In this study we found that during the early stages of somatic cell reprogramming toward a pluripotent state, specific gene expression patterns are altered. Therefore, we developed a method to generate partial-iPS (PiPS) cells by transferring four reprogramming factors (OCT4, SOX2, KLF4, and c-MYC) to human fibroblasts for 4 d. PiPS cells did not form tumors in vivo and clearly displayed the potential to differentiate into endothelial cells (ECs) in response to defined media and culture conditions. To clarify the mechanism of PiPS cell differentiation into ECs, SET translocation (myeloid leukemia-associated) (SET) similar protein (SETSIP) was indentified to be induced during somatic cell reprogramming. Importantly, when PiPS cells were treated with VEGF, SETSIP was translocated to the cell nucleus, directly bound to the VE-cadherin promoter, increasing vascular endothelialcadherin (VE-cadherin) expression levels and EC differentiation. Functionally, PiPS-ECs improved neovascularization and blood flow recovery in a hindlimb ischemic model. Furthermore, PiPS-ECs displayed good attachment, stabilization, patency, and typical vascular structure when seeded on decellularized vessel scaffolds. These findings indicate that reprogramming of fibroblasts into ECs via SETSIP and VEGF has a potential clinical application.shear stress | stem cell therapy | vascular tissue engineering

Vascular smooth muscle cells (SMCs), a major structural component of the vessel wall, not only play a key role in maintaining vascular structure but also perform various functions. During embryogenesis, SMC recruitment from their progenitors is an important step in the formation of the embryonic vascular system. SMCs in the arterial wall are mostly quiescent but can display a contractile phenotype in adults. Under pathophysiological conditions, i.e. vascular remodelling after endothelial dysfunction or damage, contractile SMCs found in the media switch to a secretory type, which will facilitate their ability to migrate to the intima and proliferate to contribute to neointimal lesions. However, recent evidence suggests that the mobilization and recruitment of abundant stem/progenitor cells present in the vessel wall are largely responsible for SMC accumulation in the intima during vascular remodelling such as neointimal hyperplasia and arteriosclerosis. Therefore, understanding the regulatory mechanisms that control SMC differentiation from vascular progenitors is essential for exploring therapeutic targets for potential clinical applications. In this article, we review the origin and differentiation of SMCs from stem/progenitor cells during cardiovascular development and in the adult, highlighting the environmental cues and signalling pathways that control phenotypic modulation within the vasculature.

Background: Apoptosis and autophagy are two closely related systems that induce cell death. Results: X-box-binding protein 1 (XBP1) mRNA splicing regulates BECLIN-1 transcriptional activation, a fundamental player in the initiation of autophagy. Conclusion: XBP1 splicing induces an autophagic response in endothelial cells. Significance: XBP1 could be used as an important pharmacological target that can regulate the autophagic machinery and endothelial cell death.

Conclusions:We developed a protocol to generate SMCs from PiPS cells through a dickkopf 3 signaling pathway, useful for generating tissue-engineered vessels. These findings provide a new insight into the mechanisms of SMC differentiation with vast therapeutic potential.

Key Words: HDAC7 Ⅲ ␤-catenin Ⅲ VEGF Ⅲ 14-3-3 Ⅲ cell cycle E ndothelial cells (ECs) are critical cellular components of blood vessels and act as selectively permeable barriers between blood and tissues. In standard physiological conditions they are compact, 1 growth inhibited, protected from apoptosis and retain full control of permeability. 2,3 In contrast, following injury, they become elongated, highly motile, and stimulate cell replication and replacement in response to growth factors. 4 Adherens junctions are formed by vascular endothelial (VE)-cadherin. VE-cadherin predominantly mediates cell contact and regulates angiogenesis by controlling EC adhesion, migration, proliferation, and survival via interactions with vascular endothelial growth factor (VEGF) receptors. 5,6 VEGF is involved in new vessel formation during embryogenesis and in proliferative diseases in adults by inducing differentiation in vascular structures and EC proliferation. 7 A number of signal transduction molecules are activated or modified in response to VEGF stimulation, such as phosphoinositide 3-kinase (PI 3-kinase) and its downstream substrates, serine/threonine kinase Akt/protein kinase B, phospholipase (PL)C␥, Src family tyrosine kinases, the Ras GTPase-activating protein, small adaptor molecule Nck, focal adhesion kinase C, extracellular signal-regulated kinase (ERK), and p38 mitogen-activated protein kinase. 8,9 ␤-Catenin is a signaling molecule that promotes cell proliferation and growth by inducing gene transcription through activation of T-cell factor/lymphoid enhancer factor (TCF/LEF), 10 Id2 (inhibitor of DNA binding 2), 11 and follistatin 12 transcription factors. The phosphorylation of ␤-catenin by casein kinase 1 (CK1) at Ser45 and by glycogen Original received May 20, 2009; resubmission received November 13, 2009; revised resubmission received February 26, 2010; accepted February 26, 2010 20 However, the detailed mechanisms of how HDAC7 is involved in these key angiogenic processes is still unclear. In this study we demonstrate that HDAC7 controls EC growth through modulation of ␤-catenin and maintains ECs in a low proliferation stage. MethodsAn expanded Methods section is available in the Online Data Supplement at http://circres.ahajournals.org. Cell CultureHuman umbilical vein endothelial cells (HUVECs) were isolated from the human umbilical cord and cultured on collagen I-coated Figure 1. Elevated HDAC7 suppresses EC proliferation via prevention of ␤-catenin translocation. A, Overexpression of HDAC7 decreases metabolism (MTT) and BrdUrd incorporation. HUVECs were uninfected (Ctl) or infected with Ad-HD7 or Ad-tTA. MTT and BrdUrd assays were performed 48 hour after infection. *PϽ0.05. B, Fluorescenceactivated cell-sorting analysis revealed that overexpression of HDAC7 in HUVECs prevents the G 1 /S phase transition. C and D, Overexpression of HDAC7 decreases cyclin D1, Id2, and TCF-1 expression at the RNA level by real-time PCR (*PϽ0.05) (C) or at the protein level by Western blot (D) 48 hours after infection. ␣-T...

Background: Induced pluripotent stem cells (iPSCs) constitute an attractive source of cells for regenerative medicine.Results: MicroRNA-21 mediates endothelial differentiation derived from iPSCs in presence of VEGF.Conclusion: MicroRNA-21 and TGF-β2 signaling pathways regulate iPSC differentiation to endothelial lineage.Significance: Elucidation of the molecular mechanisms underlying microRNA-21-regulated iPSC differentiation might provide the basic information for stem cell therapy of vascular diseases.

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Cumulatively, we provide the first evidence that DKK3 is a potent SMC differentiation factor, which might have a therapeutic effect in reducing intraplaque hemorrhage related to atherosclerotic plaque phenotype.