Evaluation of the Biocompatibility and Endothelial Differentiation Capacity of Mesenchymal Stem Cells by Polyethylene Glycol Nanogold Composites

Cardiovascular Diseases (CVDs) such as atherosclerosis, where inflammation occurs in the blood vessel wall, are one of the major causes of death worldwide. Mesenchymal Stem Cells (MSCs)-based treatment coupled with nanoparticles is considered to be a potential and promising therapeutic strategy for vascular regeneration. Thus, angiogenesis enhanced by nanoparticles is of critical concern. In this study, Polyethylene Glycol (PEG) incorporated with 43.5 ppm of gold (Au) nanoparticles was prepared for the evaluation of biological effects through in vitro and in vivo assessments. The physicochemical properties of PEG and PEG–Au nanocomposites were first characterized by UV-Vis spectrophotometry (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), and Atomic Force Microscopy (AFMs). Furthermore, the reactive oxygen species scavenger ability as well as the hydrophilic property of the nanocomposites were also investigated. Afterwards, the biocompatibility and biological functions of the PEG–Au nanocomposites were evaluated through in vitro assays. The thin coating of PEG containing 43.5 ppm of Au nanoparticles induced the least platelet and monocyte activation. Additionally, the cell behavior of MSCs on PEG–Au 43.5 ppm coating demonstrated better cell proliferation, low ROS generation, and enhancement of cell migration, as well as protein expression of the endothelialization marker CD31, which is associated with angiogenesis capacity. Furthermore, anti-inflammatory and endothelial differentiation ability were both evaluated through in vivo assessments. The evidence demonstrated that PEG–Au 43.5 ppm implantation inhibited capsule formation and facilitated the expression of CD31 in rat models. TUNEL assay also indicated that PEG–Au nanocomposites would not induce significant cell apoptosis. The above results elucidate that the surface modification of PEG–Au nanomaterials may enable them to serve as efficient tools for vascular regeneration grafts.

A functional extracellular matrix biomaterial enriched with VEGFA and bFGF as vehicle of human umbilical cord mesenchymal stem cells in skin wound healing

The construction of microvascular network is one of the greatest challenges for tissue engineering and cell therapy. Endothelial cells are essential for the construction of network of blood vessels. However, their application meets challenges in clinic due to the limited resource of autologous endothelium. Mesenchymal stem cells (MSCs) can effectively promote the angiogenesis in ischemic tissues for their abilities of endothelial differentiation and paracrine, and abundant sources. Extracellular matrix (ECM) has been widely used as an ideal biomaterial to mimic cellular microenvironment for tissue engineering due to its merits of neutrality, good biocompatibility, degradability, and controllability. In this study, a functional cell derived ECM biomaterial enriched with VEGFA and bFGF by expressing the collagen-binding domain (CBD) fused factor genes in host cells was prepared. This material could induce endothelial differentiation of human umbilical cord mesenchymal stem cells (hUCMSCs) and promote angiogenesis, which may improve the healing effect of skin injury. Our research not only provides a functional ECM material to inducing angiogenesis by inducing endothelial differentiation of hUCMSCs, but also shed light on the ubiquitous approaches to endow ECM materials different functions by enriching different factors. This study will greatly benefit tissue engineering and regenerative medicine researches.

Novel Evidence That By Employing a Two-Step Differentiation Protocol in the Presence of UM171 and Nicotinamide Acid Human Very Small Embryonic like Stem Cells (VSELs) Differentiate into Functional Endothelial Cells (ECs)

Background . Human Very small embryonic-like stem cells (VSELs) are CD133 + CD34 + small dormant stem cells with properties of self-renewal and multipotential ability to differentiate in the three-germ layers (Circulation Research 2019; 124: 208-210) and currently, more than 40 independent groups worldwide who have carefully followed the multicolor-staining cell-sorting strategy described by us (Current Protocols in Cytometry 2010 , 9.29.1-9.29.15). We have previously reported that human bone marrow (BM)-derived VSELs are able to give rise to vessel formation and endothelial differentiation (Thrombosis and Haemostasis 2015 ; 113 : 1084-1094) and several independent groups confirmed our data with human, mouse, or rat VSELs. Thus, VSELs are a promising source in regenerative medicine for the treatment of vascular diseases. Aim of the study. We aimed to develop an in vitro expansion and differentiation protocol of VSELs into endothelial cells (EC-VSELs) that will provide a clinically relevant cell therapy product without ethical problems and undesirable side effects. Materials and Methods. Highly purified by FACS from umbilical cord blood (UCB), VSELs were sorted as very small lineage-negative, CD45 -, CD34 + cells and then cultured and expanded into EC-VSELs in pro-angiogenic medium supplemented with mesodermal differentiation factors followed by stimulation by endothelial differentiation factors in the presence of UM171 and nicotinamide acid. In parallel, for comparison we expanded ECFCs from MNCs isolated from the same UCB units. The endothelial nature of the expanded VSEL-derived ECs (EC-VSELs) was tested by the expression of typical EC markers as well as by in vitro and in vivo functional angiogenic assays. Results. We report here for the first time a multistep differentiation strategy of highly purified UCB-derived VSELsThese cells after isolation by FACS were small and round, then in the presence of GSK3b inhibitor and BMP4 inducing mesodermal differentiation and high VEGF concentration to induce endothelial differentiation, VSELs enlarged and displayed extended morphology and acquired a characteristic cobblestone morphology. Finally, we have obtained a high number of cells with typical morphology of endothelial cells (EC-VSELs). By inhibiting potential mesodermal transition using TGFb inhibitor, EC-VSELs had a comparable morphology to primary human ECFCs and were characterized by tight junctions, caveolae, and Weibel-Palade Bodies, as demonstrated by transmission electron microscopy analysis of cell cultures conducted on fibrin network on the top of pericardial membranes. ECFCs differentiation was confirmed by analyzing the expression of endothelial markers by flow cytometry, and EC-VSELs were positive for PECAM1, VE-cadherin, VEGFR2, and endoglin. EC-VSELs as compared to ECFCs presented the same levels of expression of all these endothelial markers. What is important at the same time, EC-VSELs, as well as ECFCs, were negative for mesodermal marker Thy-1, confirming their endothelial phenotype. Migration properties of EC-VSELs were studied in basal conditions or in pro-angiogenic conditions using two in vitro models: wound healing assay and Trans well migration assay, and in both models EC-VSELs migration properties were similar to those of ECFCs. Next, we compared paracrine activity by evaluating growth factor and cytokine secretion profile of EC-VSELs, and noticed that the cytokine secretion by expanded VSELs was comparable to that of ECFCs. Moreover, the formation of pseudo-tubes was similar with both conditioned media. Finally, we have assessed the angiogenic capacity of EC-VSELs with a 3D in vitro sprouting assay and in vivo Matrigel plug assay. EC-VSELs display angiogenic properties but with lower potential in comparison with ECFCs which could be explained by their more primitive potential and most likely they need more time to be fully specified into the endothelial lineage. Conclusions. Based on our novel intriguing data, showing that highly purified VSELs expand efficient by employing a two-step differentiation protocol in the presence of UM171 and nicotinamide to EC-VSELs and acquire the same endothelial morphology, phenotype, and secretory potential as ECFCs as well as form functional vessels in in vitro and in vivo angiogenic assays, they could become an alternative source of ECFCs to treat vascular diseases. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Sustained Release of MiR-217 Inhibitor by Nanoparticles Facilitates MSC-Mediated Attenuation of Neointimal Hyperplasia After Vascular Injury

Mesenchymal stem cells (MSCs) have been proven capable of differentiating into endothelial cells (ECs) and increasing vascular density in mouse ischemia models. However, the therapeutic potential of MSCs in neointimal hyperplasia after vascular injury is still not fully understood. In this study, we proposed that sustained release of miR-217 inhibitor encapsulated by nanoparticles in MSCs can enhance the therapeutic effects of MSCs on alleviating neointimal hyperplasia in a standard mouse wire injury model. We intravenously administered MSCs to mice with injured arteries and examined neointimal proliferation, endothelial differentiation and senescence. We demonstrated that MSCs localized to the luminal surface of the injured artery within 24 h after injection and subsequently differentiated into endothelial cells, inhibited neointimal proliferation and migration of vascular smooth muscle cells. Transfection of MSCs with poly lactic-co-glycolic acid nanoparticles (PLGA-NP) encapsulating an miR-217 agomir abolished endothelial differentiation as well as the therapeutic effect of MSCs. On the contrary, silencing of endogenous miR-217 improved the therapeutic efficacy of MSCs. Our study provides a new strategy of augmenting the therapeutic potency of MSCs in treatment of vascular injury.

Role of TGFβ1 and WNT6 in FGF2 and BMP4-driven endothelial differentiation of murine embryonic stem cells

Embryonic stem cells (ES) are a valuable source of endothelial cells. By co-culturing ES cells with the stromal PA6 cells, the endothelial commitment can be achieved by adding exogenous FGF2 or BMP4. In this work, the molecular pathways that direct the differentiation of ES cells toward endothelium in response to FGF2 are evaluated and compared to those activated by BMP4. To this purpose the genes expression profiles of both ES/PA6 co-cultures and of pure cultures of PA6 cells were obtained by microarray technique at different time points. The bioinformatics processing of the data indicated TGFβ1 as the most represented upstream regulator in FGF2-induced endothelial commitment while WNT pathway as the most represented in BMP4-activated endothelial differentiation. Loss of function experiments were performed to validate the importance of TGFβ1 and WNT6 respectively in FGF2 and BMP4-induced endothelial differentiation. The loss of TGFβ1 expression significantly impaired the accomplishment of the endothelial commitment unless exogenous recombinant TGFβ1 was added to the culture medium. Similarly, silencing WNT6 expression partially affected the endothelial differentiation of the ES cells upon BMP4 stimulation. Such dysfunction was recovered by the addition of recombinant WNT6 to the culture medium. The ES/PA6 co-culture system recreates an in vitro complete microenvironment in which endothelial commitment is accomplished in response to alternative signals through different mechanisms. Given the importance of WNT and TGFβ1 in mediating the crosstalk between tumor and stromal cells this work adds new insights in the mechanism of tumor angiogenesis and of its possible inhibition.

Gleevec and Rapamycin Synergistically Reduce Cell Viability and Inhibit Proliferation and Angiogenic Function of Mouse Bone Marrow-Derived Endothelial Progenitor Cells

<b><i>Objective:</i></b> This study investigates the synergistic effects of Gleevec (imatinib) and rapamycin on the proliferative and angiogenic properties of mouse bone marrow-derived endothelial progenitor cells (EPCs). <b><i>Materials and Methods:</i></b> EPCs were isolated from mouse bone marrow and treated with different concentrations of Gleevec or rapamycin individually or in combination. The cell viability and proliferation were examined using the MTT assay. An analysis of cell cycle and apoptosis was performed using flow cytometry. Formation of capillary-like tubes was examined in vitro, and the protein expression of cell differentiation markers was determined using Western blot analysis. <b><i>Results:</i></b> Gleevec significantly reduced cell viability, cell proliferation, and induced cell apoptosis in EPCs. Rapamycin had similar effects on EPCs, but it did not induce cell apoptosis. The combination of Gleevec and rapamycin reduced the cell proliferation but increased cell apoptosis. Although rapamycin had no demonstratable effect on tube formation, the combined therapy of Gleevec and rapamycin significantly reduced tube formation when compared with Gleevec alone. Mechanistically, Gleevec, but not rapamycin, induced a significant elevation in caspase-3 activity in EPCs, and it attenuated the expression of the endothelial protein marker platelet-derived growth factor receptor α. Functionally, rapamycin, but not Gleevec, significantly enhanced the expression of endothelial differentiation marker proteins, while attenuating the expression of mammalian target of rapamycin signaling-related proteins. <b><i>Conclusions:</i></b> Gleevec and rapamycin synergistically suppress cell proliferation and tube formation of EPCs by inducing cell apoptosis and endothelial differentiation. Mechanistically, it is likely that rapamycin enhances the proapoptotic and antiangiogenic effects of Gleevec by promoting the endothelial differentiation of EPCs. Given that EPCs are involved in the pathogenesis of some cardiovascular diseases and critical to angiogenesis, pharmacological inhibition of EPC proliferation by combined Gleevec and rapamycin therapy may be a promising approach for suppressing cardiovascular disease pathologies associated with angiogenesis.

TBX20 Contributes to Balancing the Differentiation of Perivascular Adipose-Derived Stem Cells to Vascular Lineages and Neointimal Hyperplasia

BackgroundPerivascular adipose-derived stem cells (PVASCs) can contribute to vascular remodeling, which are also capable of differentiating into multiple cell lineages. The present study aims to investigate the mechanism of PVASC differentiation toward smooth muscle cells (SMCs) and endothelial cells (ECs) as well as its function in neointimal hyperplasia.MethodsSingle-cell sequencing and bulk mRNA sequencing were applied for searching key genes in PVASC regarding its role in vascular remodeling. PVASCs were induced to differentiate toward SMCs and ECs in vitro, which was quantitatively evaluated using immunofluorescence, quantitative real-time PCR (QPCR), and Western blot. Lentivirus transfections were performed in PVASCs to knock down or overexpress TBX20. In vivo, PVASCs transfected with lentivirus were transplanted around the guidewire injured femoral artery. Hematoxylin–eosin (H&amp;E) staining was performed to examine their effects on neointimal hyperplasia.ResultsBulk mRNA sequencing and single-cell sequencing revealed a unique expression of TBX20 in PVASCs. TBX20 expression markedly decreased during smooth muscle differentiation while it increased during endothelial differentiation of PVASCs. TBX20 knockdown resulted in the upregulation of SMC-specific marker expression and activated Smad2/3 signaling, while inhibiting endothelial differentiation. In contrast, TBX20 overexpression repressed the differentiation of PVASCs toward smooth muscle cells but promoted endothelial differentiation in vitro. Transplantation of PVASCs transfected with TBX20 overexpression lentivirus inhibited neointimal hyperplasia in a murine femoral artery guidewire injury model. On the contrary, neointimal hyperplasia significantly increased in the TBX20 knockdown group.ConclusionA subpopulation of PVASCs uniquely expressed TBX20. TBX20 could regulate SMC and EC differentiation of PVASCs in vitro. Transplantation of PVASCs after vascular injury suggested that PVASCs participated in neointimal hyperplasia via TBX20.