Blood flow and stem cells in vascular disease

Remodelers of the vascular microenvironment: The effect of biopolymeric hydrogels on vascular diseases

Vascular disease is the leading health problem worldwide. Vascular microenvironment encompasses diverse cell types, including those within the vascular wall, blood cells, stromal cells, and immune cells. Initiation of the inflammatory state of the vascular microenvironment and changes in its mechanics can profoundly affect vascular homeostasis. Biomedical materials play a crucial role in modern medicine, hydrogels, characterized by their high-water content, have been increasingly utilized as a three-dimensional interaction network. In recent times, the remarkable progress in utilizing hydrogels and understanding vascular microenvironment have enabled the treatment of vascular diseases. In this review, we give an emphasis on the utilization of hydrogels and their advantages in the various vascular diseases including atherosclerosis, aneurysm, vascular ulcers of the lower limbs and myocardial infarction. Further, we highlight the importance and advantages of hydrogels as artificial microenvironments.

Research on the Current Application Status of Magnesium Metal Stents in Human Luminal Cavities

The human body comprises various tubular structures that have essential functions in different bodily systems. These structures are responsible for transporting food, liquids, waste, and other substances throughout the body. However, factors such as inflammation, tumors, stones, infections, or the accumulation of substances can lead to the narrowing or blockage of these tubular structures, which can impair the normal function of the corresponding organs or tissues. To address luminal obstructions, stenting is a commonly used treatment. However, to minimize complications associated with the long-term implantation of permanent stents, there is an increasing demand for biodegradable stents (BDS). Magnesium (Mg) metal is an exceptional choice for creating BDS due to its degradability, good mechanical properties, and biocompatibility. Currently, the Magmaris® coronary stents and UNITY-BTM biliary stent have obtained Conformité Européene (CE) certification. Moreover, there are several other types of stents undergoing research and development as well as clinical trials. In this review, we discuss the required degradation cycle and the specific properties (anti-inflammatory effect, antibacterial effect, etc.) of BDS in different lumen areas based on the biocompatibility and degradability of currently available magnesium-based scaffolds. We also offer potential insights into the future development of BDS.

Stem cell-based therapeutic strategies for rotator cuff tendinopathy

Rotator cuff tendinopathy is a common musculoskeletal disorder that imposes significant health and economic burden. Stem cell therapy has brought hope for tendon healing in patients with final stage rotator cuff tendinopathy. Some clinical trials have confirmed the effectiveness of stem cell therapy for rotator cuff tendinopathy, but its application has not been promoted and approved. There are still many issues that should be solved prior to using stem cell therapy in clinical applications. The optimal source and dose of stem cells for rotator cuff tendinopathy should be determined. We also proposed novel prospective approaches that can overcome cell population heterogeneity and standardize patient types for stem cell applications.

The translational potential of this article

This review explores the optimal sources of stem cells for rotator cuff tendinopathy and the principles for selecting stem cell dosages. Key strategies are provided for stem cell population standardization and recipient selection.

Nanofiber-based Stretchable Electrodes for Oriented Culture and Mechanotransduction Monitoring of Smooth Muscle Cells

Vascular smooth muscle cells (SMCs) are circumferentially oriented perpendicular to the blood vessel and maintain the contractile phenotype in physiological conditions. They can sense the mechanical forces of blood vessels expanding and contracting and convert them into biochemical signals to regulate vascular homeostasis. However, the real-time monitoring of mechanically evoked biochemical response while maintaining SMC oriented growth remains an important challenge. Herein, we developed a stretchable electrochemical sensor by electrospinning aligned and elastic polyurethane (PU) nanofibers on the surface of PDMS film and further modification of conductive polymer PEDOT:PSS-LiTFSI-CoPc (PPLC) on the nanofibers (denoted as PPLC/PU/PDMS). The aligned nanofibers on the electrode surface could guide the oriented growth of SMCs and maintain the contractile phenotype, and the modification of PPLC endowed the electrode with good electrochemical sensing performance and stability under mechanical deformation. By culturing cells on the electrode surface, the oriented growth of SMCs and real-time monitoring of stretch-induced H2O2 release were achieved. On this basis, the changes of H2O2 level released by SMCs under the pathology (hypertension) and intervention of natural product resveratrol were quantitatively monitored, which will be helpful to further understand the occurrence and development of vascular-related diseases and the mechanisms of pharmaceutical intervention.

The neurovascular unit in leukodystrophies: towards solving the puzzle

The neurovascular unit (NVU) is a highly organized multicellular system localized in the brain, formed by neuronal, glial (astrocytes, oligodendrocytes, and microglia) and vascular (endothelial cells and pericytes) cells. The blood-brain barrier, a complex and dynamic endothelial cell barrier in the brain microvasculature that separates the blood from the brain parenchyma, is a component of the NVU. In a variety of neurological disorders, including Alzheimer's disease, multiple sclerosis, and stroke, dysfunctions of the NVU occurs. There is, however, a lack of knowledge regarding the NVU function in leukodystrophies, which are rare monogenic disorders that primarily affect the white matter. Since leukodystrophies are rare diseases, human brain tissue availability is scarce and representative animal models that significantly recapitulate the disease are difficult to develop. The introduction of human induced pluripotent stem cells (hiPSC) now makes it possible to surpass these limitations while maintaining the ability to work in a biologically relevant human context and safeguarding the genetic background of the patient. This review aims to provide further insights into the NVU functioning in leukodystrophies, with a special focus on iPSC-derived models that can be used to dissect neurovascular pathophysiology in these diseases.

Effects of shear stress on differentiation of stem cells into endothelial cells

Stem cell transplantation is an appealing potential therapy for vascular diseases and an indispensable key step in vascular tissue engineering. Substantial effort has been made to differentiate stem cells toward vascular cell phenotypes, including endothelial cells (ECs) and smooth muscle cells. The microenvironment of vascular cells not only contains biochemical factors that influence differentiation but also exerts hemodynamic forces, such as shear stress and cyclic strain. More recently, studies have shown that shear stress can influence the differentiation of stem cells toward ECs. A deep understanding of the responses and underlying mechanisms involved in this process is essential for clinical translation. This review highlights current data supporting the role of shear stress in stem cell differentiation into ECs. Potential mechanisms and signaling cascades for transducing shear stress into a biological signal are proposed. Further study of stem cell responses to shear stress will be necessary to apply stem cells for pharmacological applications and cardiovascular implants in the realm of regenerative medicine.

The effects of human platelet lysate versus commercial endothelial growth medium on the endothelial differentiation potential of human amniotic fluid mesenchymal stem cells

To differentiate stem cells into endothelial cells, vascular endothelia growth factors (VEGF) serve as the major signal for stimulating the cells. However, there are other cytokines or growth factors associated with endothelial cell development and differentiation. Human platelet lysate (hPL) has been a promising reagent in cell-based therapy since it is considered as a source of bioactive molecules and growth factors. The aim of this study was to investigate the in vitro differentiation of human amniotic fluid mesenchymal stem cells (hAF-MSCs) into endothelial-like cells under hPL together with VEGF or endothelial cell growth medium 2 (EGM-2), a commercially induced medium. In this study, hAF-MSCs were isolated from human amniotic fluid cells (hAFCs) using the direct adherence method. The cells expressed CD44, CD73, CD90, and HLA-ABC at high levels and expressed Oct-4 (octamer-binding transcription factor 4) at low levels. The cells were negative for CD31, CD34, CD45, CD105 and HLA-DR. This study found that hAF-MSCs induced with hPL and VEGF had the ability to differentiate into endothelial-like cells by presenting endothelial specific markers (vWF, VEGFR2 and eNOS), forming a network-like structure on Matrigel, and producing nitric oxide (NO). This outcome was similar to those of experiments involving EGM-2 induced cells. The present findings indicate that hPL + VEGF can induce hAF-MSCs to express endothelial cell characteristics. Our findings represent an important step forward in the development of a clinically compliant process for the production of endothelial cell-derived hAF-MSCs, and their subsequent testing in future clinical trials.

Berberine inhibits proliferation and apoptosis of vascular smooth muscle cells induced by mechanical stretch via the PDI/ERS and MAPK pathways

AIMS

We recently demonstrated that mechanical stretch increases the proliferation and apoptosis of vascular smooth muscle cells (VSMCs) by activating the protein disulfide isomerase (PDI) redox system, thus accelerating atherosclerotic lesion formation in the transplanted vein. At present, there are no efficient intervention measures to prevent this phenomenon. Berberine inhibits pathological vascular remodeling caused by hypertension, but the underlying mechanism is controversial. Herein, we investigate the role of berberine and the underlying mechanism of its effects on mechanical stretch-induced VSMC proliferation and apoptosis.

MAIN METHODS

Mouse VSMCs cultivated on flexible membranes were pretreated for 1 h with one of the following substances: berberine, PDI inhibitor bacitracin, MAPK inhibitors, or ERS inhibitor 4-PBA. VSMCs were then subjected to mechanical stretch. Immunofluorescence and western blot were used to detect proliferation and apoptosis, as well as to analyze signaling pathways in VSMCs.

KEY FINDINGS

Our results showed that berberine inhibits the PDI-endoplasmic reticulum stress system, thereby attenuating the simultaneous increase of VSMC proliferation and apoptosis in response to mechanical stretch. Interestingly, MAPK inhibitors PD98059, SP600125, and SB202190 significantly reduced the activation of ERS signaling cascades, and their combination with berberine had additive effects. The ERS inhibitor 4-PBA reduced PDI activation and ERS signaling, but not MAPK phosphorylation. Moreover, caspase-3 and caspase-12 were downregulated by berberine.

SIGNIFICANCE

These results illustrate a novel mechanism of action of berberine that has practical implications. Our data provide important insights for the prevention and treatment of vascular remodeling and diseases caused by mechanical stretching during hypertension.

Biomechanical signal communication in vascular smooth muscle cells

Biomechanical stresses are closely associated with cardiovascular development and diseases. In vivo, vascular smooth muscle cells are constantly stimulated by biomechanical factors caused by increased blood pressure leading to the non-specific activation of cell transmembrane proteins. Thus, various intracellular signal molecules are simultaneously activated via signaling cascades, which are closely related to alterations in the differentiation, phenotype, inflammation, migration, pyroptosis, calcification, proliferation, and apoptosis of vascular smooth muscle cells. Meanwhile, mechanical stress-induced miRNAs and epigenetics modification on vascular smooth muscle cells play critical roles as well. Eventually, the overall pathophysiology of the cells is altered, resulting in the development of many major clinical diseases, including hypertension, atherosclerosis, grafted venous atherosclerosis, and aneurysm, among others. In this paper, important advances in mechanical signal communication in vascular smooth muscle cells are reviewed.

Oscillating shear stress mediates mesenchymal transdifferentiation of EPCs by the Kir2.1 channel

Although endothelial progenitor cells (EPCs) are considered to be an essential source of vascular endothelial repair, their bidirectional differentiation determines that they play a double-edged role in the restoration of endothelial injury. In this research, we investigated the effect of Kir2.1 ion channel on the transdifferentiation of endothelial progenitor cells (EPCs) under the oscillating shear stress (OSS) and the molecular mechanisms underlying the pathological vascular remodeling. EPCs were treated with OSS (± 3.5 dynes/cm², 1 Hz) simulated with the parallel flow chamber system. The results have shown that OSS promoted the expression of α-SMA and SM22, markers of mesenchymal cells on EPCs. Moreover, OSS also increased expression of Kir2.1 in EPCs. The down-regulation of Kir2.1 reduced OSS-induced EPC mesenchymal transdifferentiation. The overexpression of Kir2.1 suppressed the angiogenic abilities of EPCs in vitro. In parallel, the overexpression of Kir2.1 on EPCs thickened the carotid tunica intima in rat carotid artery balloon injured model in vivo. Taken together, those data indicated that the OSS could facilitate the transdifferentiation of EPCs by increasing Kir2.1 expression. This study provides a novel insight into the pathogenesis of cardiovascular diseases and gives evidence for Kir2.1 as a potential therapeutic target.

Visualizing the Fate of Intra-Articular Injected Mesenchymal Stem Cells In Vivo in the Second Near-Infrared Window for the Effective Treatment of Supraspinatus Tendon Tears

Mesenchymal stem cells (MSCs) are capable of exerting strong therapeutic potential for the treatment of supraspinatus tendon tear. However, MSC therapy remains underutilized and perhaps underrated due to the limited evidence of dynamic visualization of cellular behavior in vivo. Here, second near-infrared fluorescence imaging with biocompatible PbS quantum dots (QDs) provides a cellular migration map and information on the biodistribution and clearance processes of three densities of intra-articularly injected, labeled MSCs to treat supraspinatus tendon tear in mice. Intra-articular injection avoids entrapment of MSCs by filter organs and reduces the QD-induced organ toxicity. Notably, the MSCs share a similar migration direction, but the moderate density group is somewhat more efficient, showing the longest residence time and highest cell retention rate around the footprint during the repair stage. Furthermore, quantitative kinetic investigation demonstrates that labeled MSCs are cleared by feces and urine. Histomorphometric analysis demonstrates that the moderate density group achieves maximum therapeutic effect and labeled MSCs do not induce any injury or inflammation to major organs, which suggests that administration of too many or few MSCs may decrease their effectiveness. Such an imaging approach provides spatiotemporal evidence for response to MSC therapy in vivo, facilitating the optimization of MSC therapy.

MicroRNA-129-1-3p regulates cyclic stretch-induced endothelial progenitor cell differentiation by targeting Runx2

Endothelial progenitor cells (EPCs) are vital to the recovery of endothelial function and maintenance of vascular homeostasis. EPCs mobilize to sites of vessel injury and differentiate into mature endothelial cells (ECs). Locally mobilized EPCs are exposed to cyclic stretch caused by blood flow, which is important for EPC differentiation. MicroRNAs (miRNAs) have emerged as key regulators of several cellular processes. However, the role of miRNAs in cyclic stretch-induced EPC differentiation remains unclear. Here, we investigate the effects of microRNA-129-1-3p (miR-129-1-3p) and its novel target Runt-related transcription factor 2 (Runx2) on EPC differentiation induced by cyclic stretch. Bone marrow-derived EPCs were exposed to cyclic stretch with a magnitude of 5% (which mimics physiological mechanical stress) at a constant frequency of 1.25 Hz for 24 hours. The results from a miRNA array revealed that cyclic stretch significantly decreased miR-129-1-3p expression. Furthermore, we found that downregulation of miR-129-1-3p during cyclic stretch-induced EPC differentiation toward ECs. Meanwhile, expression of Runx2, a putative target gene of miR-129-1-3p, was increased as a result of cyclic stretch. A 3'UTR reporter assay validated Runx2 as a direct target of miR-129-1-3p. Furthermore, small interfering RNA (siRNA)-mediated knockdown of Runx2 inhibited EPC differentiation into ECs and attenuated EPC tube formation via modulation of vascular endothelial growth factor (VEGF) secretion from EPCs in vitro. Our findings demonstrated that cyclic stretch suppresses miR-129-1-3p expression, which in turn activates Runx2 and VEGF to promote endothelial differentiation of EPCs and angiogenesis. Therefore, targeting miR-129-1-3p and Runx2 may be a potential therapeutic strategy for treating vessel injury.

Histone Deacetylase 7-Derived Peptides Play a Vital Role in Vascular Repair and Regeneration

Cardiovascular disease is a leading cause of morbidity and mortality globally. Accumulating evidence indicates that local resident stem/progenitor cells play an important role in vascular regeneration. Recently, it is demonstrated that a histone deacetylase 7-derived 7-amino acid peptide (7A, MHSPGAD) is critical in modulating the mobilization and orientated differentiation of these stem/progenitor cells. Here, its therapeutic efficacy in vascular repair and regeneration is evaluated. In vitro functional analyses reveal that the 7A peptide, in particular phosphorylated 7A (7Ap, MH[pSer]PGAD), could increase stem cell antigen-1 positive (Sca1+) vascular progenitor cell (VPC) migration and differentiation toward an endothelial cell lineage. Furthermore, local delivery of 7A as well as 7Ap could enhance angiogenesis and ameliorate vascular injury in ischaemic tissues; these findings are confirmed in a femoral artery injury model and a hindlimb ischaemia model, respectively. Importantly, sustained delivery of 7A, especially 7Ap, from tissue-engineered vascular grafts could attract Sca1+-VPC cells into the grafts, contributing to endothelialization and intima/media formation in the vascular graft. These results suggest that this novel type of peptides has great translational potential in vascular regenerative medicine.

Atherosclerosis is a vascular stem cell disease caused by insulin

The present article proposes the hypothesis that when multipotent vascular stem cells are exposed to excessive insulin in a rhythmic pattern of sharply rising and falling concentrations, their differentiation is misdirected toward adipogenic and osteogenic cell lineages. This results in plaque-like accumulation of adipocytes with fat and cholesterol deposition from adipocyte debris, and osteogenic (progenitor) cells with a calcified matrix in advanced lesions. The ingrowth of capillaries and infiltration with macrophages, which upon uptake of lipids turn into foam cells, are unspecific pro-resolving reactions. Epidemiological, histopathological, pharmacological, and experimental evidence in favour of this hypothesis is summarised.

Biodiversity of CS–proteoglycan sulphation motifs: chemical messenger recognition modules with roles in information transfer, control of cellular behaviour and tissue morphogenesis

Chondroitin sulphate (CS) glycosaminoglycan chains on cell and extracellular matrix proteoglycans (PGs) can no longer be regarded as merely hydrodynamic space fillers. Overwhelming evidence over recent years indicates that sulphation motif sequences within the CS chain structure are a source of significant biological information to cells and their surrounding environment. CS sulphation motifs have been shown to interact with a wide variety of bioactive molecules, e.g. cytokines, growth factors, chemokines, morphogenetic proteins, enzymes and enzyme inhibitors, as well as structural components within the extracellular milieu. They are therefore capable of modulating a panoply of signalling pathways, thus controlling diverse cellular behaviours including proliferation, differentiation, migration and matrix synthesis. Consequently, through these motifs, CS PGs play significant roles in the maintenance of tissue homeostasis, morphogenesis, development, growth and disease. Here, we review (i) the biodiversity of CS PGs and their sulphation motif sequences and (ii) the current understanding of the signalling roles they play in regulating cellular behaviour during tissue development, growth, disease and repair.

Microparticles of healthy origins improve endothelial progenitor cell dysfunction via microRNA transfer in an atherosclerotic hamster model

AIM

In this study, we aimed: (i) to obtain and functionally characterize the cultures of late endothelial progenitor cells (EPCs) from the animal blood; (ii) to investigate the potential beneficial effects of circulating microparticles (MPs) of healthy origins on EPC dysfunctionality in atherosclerosis as well as involved mechanisms.

METHODS

Late EPCs were obtained and expanded in culture from peripheral blood isolated from two animal groups: hypertensive-hyperlipidaemic (HH) and control (C) hamsters. In parallel experiments, late EPC cultures from HH were incubated with MPs from C group.

RESULTS

The results showed that late EPCs display endothelial cell phenotype: (i) have ability to uptake 1,1-dioctadecyl-3,3,3,3 tetramethylindocarbocyanine-labelled acetylated low-density lipoprotein and Ulex europaeus agglutinin lectin-1; (ii) express CD34, CD133, KDR, CD144, vWF, Tie-2. Late EPCs from HH exhibited different morphological and functional characteristics compared to control: (i) are smaller and irregular in shape; (ii) present decreased endothelial surface marker expression; (iii) display reduced proliferation, migration and adhesion; (iv) lose ability to organize themselves into tubular structures and integrate into vascular network; (v) have diminished function of inward rectifier potassium channels. The incubation of late EPCs with MPs improved EPC functionality by miR-10a, miR-21, miR-126, miR-146a, miR-223 transfer and IGF-1 expression activation; the kinetic study of MP incorporation into EPCs demonstrated MP uptake by EPCs followed by the miRNA transfer.

CONCLUSION

The data reveal that late EPCs from atherosclerotic model exhibit distinctive features and are dysfunctional, and their function recovery can be supported by MP ability to transfer miRNAs. These findings bring a new light on the vascular repair in atherosclerosis.

Plasma stem cell factor levels are associated with risk of cardiovascular disease and death

OBJECTIVE

Stem cell factor (SCF) is a key growth factor for several types of stem and progenitor cells. There is experimental evidence that such cells are of importance for maintaining the integrity of the cardiovascular system. We investigated the association between circulating levels of SCF and risk for development of cardiovascular events and death.

METHODS

SCF was analysed by the proximity extension assay technique in plasma from 4742 subjects participating in the Malmö Diet and Cancer Study. Cardiovascular events and death were monitored through national registers with a mean follow-up time of 19.2 years.

RESULTS

Subjects with high baseline levels of SCF had lower cardiovascular (n = 340) and all-cause mortality (n = 1159) as well as a lower risk of heart failure (n = 177), stroke (n = 318) and myocardial infarction (n = 452). Smoking, diabetes and high alcohol consumption were associated with lower levels of SCF. Single nucleotide polymorphisms in the gene region encoding PDX1 C-terminal inhibiting factor 1 (PCIF1) and matrix metalloproteinase-9 were associated with plasma SCF levels. The highest SCF quartile remained independently associated with a lower risk of a lower risk of cardiovascular [hazard ratio and 95% confidence interval 0.59 (0.43-0.81)] and all-cause mortality [0.68 (0.57-0.81)], heart failure [0.50 (0.31-0.80)] and stroke [0.66 (0.47-0.92)], but not with MI [0.96 (0.72-1.27)] as compared with the lowest quartile when adjusting for traditional cardiovascular risk factors in Cox proportional hazard regression models.

CONCLUSIONS

This prospective population-based study demonstrates that subjects with high levels of SCF have a lower risk of cardiovascular events and death. The findings provide clinical support for a protective role of SCF in maintaining cardiovascular integrity.

Cell Based Therapeutic Approach in Vascular Surgery: Application and Review

Multipotent stem cells - such as mesenchymal stem/stromal cells and stem cells derived from different sources like vascular wall are intensely studied to try to rapidly translate their discovered features from bench to bedside. Vascular wall resident stem cells recruitment, differentiation, survival, proliferation, growth factor production, and signaling pathways transduced were analyzed. We studied biological properties of vascular resident stem cells and explored the relationship from several factors as Matrix Metalloproteinases (MMPs) and regulations of biological, translational and clinical features of these cells. In this review we described a translational and clinical approach to Adult Vascular Wall Resident Multipotent Vascular Stem Cells (VW-SCs) and reported their involvement in alternative clinical approach as cells based therapy in vascular disease like arterial aneurysms or peripheral arterial obstructive disease.

Deleterious effects of tributyltin on porcine vascular stem cells physiology

The vascular functional and structural integrity is essential for the maintenance of the whole organism and it has been demonstrated that different types of vascular progenitor cells resident in the vessel wall play an important role in this process. The purpose of the present research was to observe the effect of tributyltin (TBT), a risk factor for vascular disorders, on porcine Aortic Vascular Precursor Cells (pAVPCs) in term of cytotoxicity, gene expression profile, functionality and differentiation potential. We have demonstrated that pAVPCs morphology deeply changed following TBT treatment. After 48h a cytotoxic effect has been detected and Annexin binding assay demonstrated that TBT induced apoptosis. The transcriptional profile of characteristic pericyte markers has been altered: TBT 10nM substantially induced alpha-SMA, while, TBT 500nM determined a significant reduction of all pericyte markers. IL-6 protein detected in the medium of pAVPCs treated with TBT at both doses studied and with a dose response. TBT has interfered with normal pAVPC functionality preventing their ability to support a capillary-like network. In addition TBT has determined an increase of pAVPC adipogenic differentiation. In conclusion in the present paper we have demonstrated that TBT alters the vascular stem cells in terms of structure, functionality and differentiating capability, therefore effects of TBT in blood should be deeply explored to understand the potential vascular risk associated with the alteration of vascular stem cell physiology.

Pediatric cardiovascular grafts: historical perspective and future directions

Tissue-engineered cardiovascular patches, cardiac valves, and great vessels are emerging solutions for the surgical treatment of congenital cardiovascular abnormalities due to their potential for adapting with the growing child. The ideal pediatric cardiovascular patch/graft is non-thrombogenic, phenotypically compatible, and matches the compliance and mechanical strength of the native tissue, both initially and throughout growth. Bottom-up tissue engineering approaches, in which three-dimensional tissue is built layer-by-layer from scaffold-less cell sheets in vitro, offer an exciting potential solution. Cell source variability, sheet patterning, and scaffold-less fabrication are promising advantages offered by this approach. Here we review the latest developments and next steps in bottom-up tissue engineering targeted at meeting the necessary design criteria for successful pediatric cardiac tissue-engineered grafts.

Decreased levels of stem cell factor in subjects with incident coronary events

BACKGROUND

It has been proposed that vascular progenitor cells play an important role in vascular repair, but their possible clinical importance in cardiovascular disease has not been fully characterized. Vascular endothelial growth factor A, placental growth factor and stem cell factor (SCF) are three growth factors that are important in recruiting vascular progenitor cells. In this study, we investigated the association between the plasma levels of these growth factors and incident coronary events (CEs).

METHODS

Levels of the three growth factors were measured using the proximity extension assay technique in baseline plasma samples from 384 subjects with a first CE (mean follow-up 14.0 ± 4.3 years) and 409 event-free control subjects matched by sex and age, as well as in homogenates from 201 endarterectomy specimens.

RESULTS

After controlling for known cardiovascular disease risk factors in a Cox regression model, subjects in the lowest SCF tertile had a hazard ratio of 1.70 (95% confidence interval 1.14-2.54) compared with subjects in the highest SCF tertile. Lower SCF levels were also associated with more severe carotid disease, less fibrous atherosclerotic plaques and an increased incidence of heart failure. Expression of the SCF receptor c-kit was demonstrated in the subendothelial layer and fibrous cap of human atherosclerotic plaques. Smokers and subjects with diabetes had decreased levels of SCF compared with control subjects.

CONCLUSION

To our knowledge, this is the first clinical study to provide evidence to support a key role for SCF and progenitor cells in vascular repair. We suggest that the SCF-c-kit pathway may be a promising biomarker and therapeutic target in cardiovascular disease.

Stem cell-derived vasculature: A potent and multidimensional technology for basic research, disease modeling, and tissue engineering

Proper blood vessel networks are necessary for constructing and re-constructing tissues, promoting wound healing, and delivering metabolic necessities throughout the body. Conversely, an understanding of vascular dysfunction has provided insight into the pathogenesis and progression of diseases both common and rare. Recent advances in stem cell-based regenerative medicine - including advances in stem cell technologies and related progress in bioscaffold design and complex tissue engineering - have allowed rapid advances in the field of vascular biology, leading in turn to more advanced modeling of vascular pathophysiology and improved engineering of vascularized tissue constructs. In this review we examine recent advances in the field of stem cell-derived vasculature, providing an overview of stem cell technologies as a source for vascular cell types and then focusing on their use in three primary areas: studies of vascular development and angiogenesis, improved disease modeling, and the engineering of vascularized constructs for tissue-level modeling and cell-based therapies.

3D Scaffolds with Different Stiffness but the Same Microstructure for Bone Tissue Engineering

A growing body of evidence has shown that extracellular matrix (ECM) stiffness can modulate stem cell adhesion, proliferation, migration, differentiation, and signaling. Stem cells can feel and respond sensitively to the mechanical microenvironment of the ECM. However, most studies have focused on classical two-dimensional (2D) or quasi-three-dimensional environments, which cannot represent the real situation in vivo. Furthermore, most of the current methods used to generate different mechanical properties invariably change the fundamental structural properties of the scaffolds (such as morphology, porosity, pore size, and pore interconnectivity). In this study, we have developed novel three-dimensional (3D) scaffolds with different degrees of stiffness but the same 3D microstructure that was maintained by using decellularized cancellous bone. Mixtures of collagen and hydroxyapatite [HA: Ca10(PO4)6(OH)2] with different proportions were coated on decellularized cancellous bone to vary the stiffness (local stiffness, 13.00 ± 5.55 kPa, 13.87 ± 1.51 kPa, and 37.7 ± 19.6 kPa; bulk stiffness, 6.74 ± 1.16 kPa, 8.82 ± 2.12 kPa, and 23.61 ± 8.06 kPa). Microcomputed tomography (μ-CT) assay proved that there was no statistically significant difference in the architecture of the scaffolds before or after coating. Cell viability, osteogenic differentiation, cell recruitment, and angiogenesis were determined to characterize the scaffolds and evaluate their biological responses in vitro and in vivo. The in vitro results indicate that the scaffolds developed in this study could sustain adhesion and growth of rat mesenchymal stem cells (MSCs) and promote their osteogenic differentiation. The in vivo results further demonstrated that these scaffolds could help to recruit MSCs from subcutaneous tissue, induce them to differentiate into osteoblasts, and provide the 3D environment for angiogenesis. These findings showed that the method we developed can build scaffolds with tunable mechanical properties almost without variation in 3D microstructure. These preparations not only can provide a cell-free scaffold with optimal matrix stiffness to enhance osteogenic differentiation, cell recruitment, and angiogenesis in bone tissue engineering but also have significant implications for studies on the effects of matrix stiffness on stem cell differentiation in 3D environments.

Vascular stem/progenitor cells: current status of the problem

Stem/progenitor cells residing in the vascular wall of post-natal vessels play a crucial role in angiogenesis and vascular regeneration after damage. There are four major populations of vascular-resident stem/progenitor cells with differentiated clonogenic and proliferative potential, namely mesenchymal stem cells, pericytes, endothelial progenitor cells, and smooth muscle progenitor cells. These progenitors reside in vascular stem cell niches, which are more likely to be in the adventitia, a vascular wall layer in which increased concentration of stem cell surface markers has been shown. Indeed, vascular resident progenitors are not uniformly distributed across the vessel wall and the circulatory system. The heterogeneity of such a distribution could contribute to the differentiated susceptibility of various vessel regions to chronic vascular diseases such as atherosclerosis. In cardiovascular pathology, adult vascular resident progenitors could play either a negative or a positive role.

Biomechanical strain induces elastin and collagen production in human pluripotent stem cell-derived vascular smooth muscle cells

Blood vessels are subjected to numerous biomechanical forces that work harmoniously but, when unbalanced because of vascular smooth muscle cell (vSMC) dysfunction, can trigger a wide range of ailments such as cerebrovascular, peripheral artery, and coronary artery diseases. Human pluripotent stem cells (hPSCs) serve as useful therapeutic tools that may help provide insight on the effect that such biomechanical stimuli have on vSMC function and differentiation. In this study, we aimed to examine the effect of biomechanical strain on vSMCs derived from hPSCs. The effects of two types of tensile strain on hPSC-vSMC derivatives at different stages of differentiation were examined. The derivatives included smooth muscle-like cells (SMLCs), mature SMLCs, and contractile vSMCs. All vSMC derivatives aligned perpendicularly to the direction of cyclic uniaxial strain. Serum deprivation and short-term uniaxial strain had a synergistic effect in enhancing collagen type I, fibronectin, and elastin gene expression. Furthermore, long-term uniaxial strain deterred collagen type III gene expression, whereas long-term circumferential strain upregulated both collagen type III and elastin gene expression. Finally, long-term uniaxial strain downregulated extracellular matrix (ECM) expression in more mature vSMC derivatives while upregulating elastin in less mature vSMC derivatives. Overall, our findings suggest that in vitro application of both cyclic uniaxial and circumferential tensile strain on hPSC-vSMC derivatives induces cell alignment and affects ECM gene expression. Therefore, mechanical stimulation of hPSC-vSMC derivatives using tensile strain may be important in modulating the phenotype and thus the function of vSMCs in tissue-engineered vessels.

Adult vascular wall resident multipotent vascular stem cells, matrix metalloproteinases, and arterial aneurysms

Evidences have shown the presence of multipotent stem cells (SCs) at sites of arterial aneurysms: they can differentiate into smooth muscle cells (SMCs) and are activated after residing in a quiescent state in the vascular wall. Recent studies have implicated the role of matrix metalloproteinases in the pathogenesis of arterial aneurysms: in fact the increased synthesis of MMPs by arterial SMCs is thought to be a pivotal mechanism in aneurysm formation. The factors and signaling pathways involved in regulating wall resident SC recruitment, survival, proliferation, growth factor production, and differentiation may be also related to selective expression of different MMPs. This review explores the relationship between adult vascular wall resident multipotent vascular SCs, MMPs, and arterial aneurysms.

Redox regulation of endothelial cell fate

Endothelial cells (ECs) are present throughout blood vessels and have variable roles in both physiological and pathological settings. EC fate is altered and regulated by several key factors in physiological or pathological conditions. Reactive nitrogen species and reactive oxygen species derived from NAD(P)H oxidases, mitochondria, or nitric oxide-producing enzymes are not only cytotoxic but also compose a signaling network in the redox system. The formation, actions, key molecular interactions, and physiological and pathological relevance of redox signals in ECs remain unclear. We review the identities, sources, and biological actions of oxidants and reductants produced during EC function or dysfunction. Further, we discuss how ECs shape key redox sensors and examine the biological functions, transcriptional responses, and post-translational modifications evoked by the redox system in ECs. We summarize recent findings regarding the mechanisms by which redox signals regulate the fate of ECs and address the outcome of altered EC fate in health and disease. Future studies will examine if the redox biology of ECs can be targeted in pathophysiological conditions.

TGF-β prevents phosphate-induced osteogenesis through inhibition of BMP and Wnt/β-catenin pathways

BACKGROUND

Transforming growth factor-β (TGF-β) is a key cytokine during differentiation of mesenchymal stem cells (MSC) into vascular smooth muscle cells (VSMC). High phosphate induces a phenotypic transformation of vascular smooth muscle cells (VSMC) into osteogenic-like cells. This study was aimed to evaluate signaling pathways involved during VSMC differentiation of MSC in presence or not of high phosphate.

RESULTS

Our results showed that TGF-β induced nuclear translocation of Smad3 as well as the expression of vascular smooth muscle markers, such as smooth muscle alpha actin, SM22α, myocardin, and smooth muscle-myosin heavy chain. The addition of high phosphate to MSC promoted nuclear translocation of Smad1/5/8 and the activation of canonical Wnt/β-catenin in addition to an increase in BMP-2 expression, calcium deposition and alkaline phosphatase activity. The administration of TGF-β to MSC treated with high phosphate abolished all these effects by inhibiting canonical Wnt, BMP and TGF-β pathways. A similar outcome was observed in high phosphate-treated cells after the inhibition of canonical Wnt signaling with Dkk-1. Conversely, addition of both Wnt/β-catenin activators CHIR98014 and lithium chloride enhanced the effect of high phosphate on BMP-2, calcium deposition and alkaline phosphatase activity.

CONCLUSIONS

Full VSMC differentiation induced by TGF-β may not be achieved when extracellular phosphate levels are high. Moreover, TGF-β prevents high phosphate-induced osteogenesis by decreasing the nuclear translocation of Smad 1/5/8 and avoiding the activation of Wnt/β-catenin pathway.

Nuclear reprogramming and its role in vascular smooth muscle cells

In general terms, "nuclear reprogramming" refers to a change in gene expression profile that results in a significant switch in cellular phenotype. Nuclear reprogramming was first addressed by pioneering studies of cell differentiation during embryonic development. In recent years, nuclear reprogramming has been studied in great detail in the context of experimentally controlled dedifferentiation and transdifferentiation of mammalian cells for therapeutic purposes. In this review, we present a perspective on nuclear reprogramming in the context of spontaneous, pathophysiological phenotypic switch of vascular cells occurring in the atherosclerotic lesion. In particular, we focus on the current knowledge of epigenetic mechanisms participating in the extraordinary flexibility of the gene expression profile of vascular smooth muscle cells and other cell types participating in atherogenesis. Understanding how epigenetic changes participate in vascular cell plasticity may lead to effective therapies based on the remodelling of the vascular architecture.