generation-and-grafting-of-tissue-engineered-vessels-in-a-mouse-model

Generation and Grafting of Tissue-engineered Vessels in a Mouse Model

The construction of vascular conduits is a fundamental strategy for surgical repair of damaged and injured vessels resulting from cardiovascular diseases. ...

King's College London BHF Centre

Histone deacetylase (HDAC)7 is expressed in the early stages of embryonic development and may play a role in endothelial function.

Histone deacetylase 7 controls endothelial cell growth through modulation of beta-catenin.

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 endothelial-cadherin (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.

Direct reprogramming of fibroblasts into endothelial cells capable of angiogenesis and reendothelialization in tissue-engineered vessels.

Sustained activation of X-box-binding protein 1 (XBP1) results in endothelial cell (EC) apoptosis and atherosclerosis development. The present study provides evidence that XBP1 mRNA splicing triggered an autophagic response in ECs by inducing autophagic vesicle formation and markers of autophagy BECLIN-1 and microtubule-associated protein 1 light chain 3β (LC3-βII). Endostatin activated autophagic gene expression through XBP1 mRNA splicing in an inositol-requiring enzyme 1α (IRE1α)-dependent manner. Knockdown of XBP1 or IRE1α by shRNA in ECs ablated endostatin-induced autophagosome formation. Importantly, data from arterial vessels from XBP1 EC conditional knock-out (XBP1eko) mice demonstrated that XBP1 deficiency in ECs reduced the basal level of LC3β expression and ablated response to endostatin. Chromatin immunoprecipitation assays further revealed that the spliced XBP1 isoform bound directly to the BECLIN-1 promoter at the region from nt -537 to -755. BECLIN-1 deficiency in ECs abolished the XBP1-induced autophagy response, whereas spliced XBP1 did not induce transcriptional activation of a truncated BECLIN-1 promoter. These results suggest that XBP1 mRNA splicing triggers an autophagic signal pathway through transcriptional regulation of BECLIN-1.

XBP1 mRNA splicing triggers an autophagic response in endothelial cells through BECLIN-1 transcriptional activation.

Smooth muscle cells (SMCs) are a key component of tissue-engineered vessels. However, the sources by which they can be isolated are limited.

Smooth muscle cells differentiated from reprogrammed embryonic lung fibroblasts through DKK3 signaling are potent for tissue engineering of vascular grafts.

Sirolimus-eluting stent therapy has achieved considerable success in overcoming coronary artery restenosis. However, there remain a large number of patients presenting with restenosis after the treatment, and the source of its persistence remains unclarified. Although recent evidence supports the contribution of vascular stem/progenitor cells in restenosis formation, their functional and molecular responses to sirolimus are largely unknown.

Sirolimus stimulates vascular stem/progenitor cell migration and differentiation into smooth muscle cells via epidermal growth factor receptor/extracellular signal-regulated kinase/β-catenin signaling pathway.

Finding a suitable cell source for endothelial cells (ECs) for cardiovascular regeneration is a challenging issue for regenerative medicine. In this paper, we describe a novel mechanism regulating induced pluripotent stem cells (iPSC) differentiation into ECs, with a particular focus on miRNAs and their targets. We first established a protocol using collagen IV and VEGF to drive the functional differentiation of iPSCs into ECs and compared the miRNA signature of differentiated and undifferentiated cells. Among the miRNAs overrepresented in differentiated cells, we focused on microRNA-21 (miR-21) and studied its role in iPSC differentiation. Overexpression of miR-21 in predifferentiated iPSCs induced EC marker up-regulation and in vitro and in vivo capillary formation; accordingly, inhibition of miR-21 produced the opposite effects. Importantly, miR-21 overexpression increased TGF-β2 mRNA and secreted protein level, consistent with the strong up-regulation of TGF-β2 during iPSC differentiation. Indeed, treatment of iPSCs with TGFβ-2 induced EC marker expression and in vitro tube formation. Inhibition of SMAD3, a downstream effector of TGFβ-2, strongly decreased VE-cadherin expression. Furthermore, TGFβ-2 neutralization and knockdown inhibited miR-21-induced EC marker expression. Finally, we confirmed the PTEN/Akt pathway as a direct target of miR-21, and we showed that PTEN knockdown is required for miR-21-mediated endothelial differentiation. In conclusion, we elucidated a novel signaling pathway that promotes the differentiation of iPSC into functional ECs suitable for regenerative medicine applications.

Endothelial lineage differentiation from induced pluripotent stem cells is regulated by microRNA-21 and transforming growth factor β2 (TGF-β2) pathways.

Article	Year
Histone deacetylase 7 controls endothelial cell growth through modulation of beta-catenin. Circulation research\| PubMed ID: 20224040	2010
Direct reprogramming of fibroblasts into endothelial cells capable of angiogenesis and reendothelialization in tissue-engineered vessels. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 22869753	2012
XBP1 mRNA splicing triggers an autophagic response in endothelial cells through BECLIN-1 transcriptional activation. The Journal of biological chemistry\| PubMed ID: 23184933	2013
Smooth muscle cells differentiated from reprogrammed embryonic lung fibroblasts through DKK3 signaling are potent for tissue engineering of vascular grafts. Circulation research\| PubMed ID: 23529184	2013
Sirolimus stimulates vascular stem/progenitor cell migration and differentiation into smooth muscle cells via epidermal growth factor receptor/extracellular signal-regulated kinase/β-catenin... Arteriosclerosis, thrombosis, and vascular biology\| PubMed ID: 23928863	2013
Endothelial lineage differentiation from induced pluripotent stem cells is regulated by microRNA-21 and transforming growth factor β2 (TGF-β2) pathways. The Journal of biological chemistry\| PubMed ID: 24356956	2014

Eirini Karamariti

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