Resident phenotypically modulated vascular smooth muscle cells in healthy human arteries

Human iPSC-derived mesenchymal stem cells encapsulated in PEGDA hydrogels mature into valve interstitial-like cells

Despite recent advances in tissue engineered heart valves (TEHV), a major challenge is identifying a cell source for seeding TEHV scaffolds. Native heart valves are durable because valve interstitial cells (VICs) maintain tissue homeostasis by synthesizing and remodeling the extracellular matrix. This study demonstrates that induced pluripotent stem cells (iPSC)-derived mesenchymal stem cells (iMSCs) can be derived from iPSCs using a feeder-free protocol and then further matured into VICs by encapsulation within 3D hydrogels. The differentiation efficiency was characterized using flow cytometry, immunohistochemistry staining, and trilineage differentiation. Using our feeder-free differentiation protocol, iMSCs were differentiated from iPSCs and had CD90+, CD44+, CD71+, αSMA+, and CD45- expression. Furthermore, iMSCs underwent trilineage differentiation when cultured in induction media for 21 days. iMSCs were then encapsulated in poly(ethylene glycol)diacrylate (PEGDA) hydrogels grafted with adhesion peptide (RGDS) to promote remodeling and further maturation into VIC-like cells. VIC phenotype was assessed by the expression of alpha-smooth muscle actin (αSMA), vimentin, and collagen production after 28 days. When MSC-derived cells were encapsulated in PEGDA hydrogels that mimic the leaflet modulus, a decrease in αSMA expression and increase in vimentin was observed. In addition, iMSCs synthesized collagen type I after 28 days in 3D hydrogel culture. Thus, the results from this study suggest that iMSCs may be a promising cell source for TEHV.

STATEMENT OF SIGNIFICANCE

Developing a suitable cell source is a critical component for the success and durability of tissue engineered heart valves. The significance of this study is the generation of iPSCs-derived mesenchymal stem cells (iMSCs) that have the capacity to mature into valve interstitial-like cells when introduced into a 3D cell culture designed to mimic the layers of the valve leaflet. iMSCs were generated using a feeder-free protocol, which is one major advantage over other methods, as it is more clinically relevant. In addition to generating a potential new cell source for heart valve tissue engineering, this study also highlights the importance of a 3D culture environment to influence cell phenotype and function.

Susceptiveness of Vitamin K epOxide Reductase Complex Subunit 1 Gene Polymorphism in Essential Hypertension

BACKGROUND

Essential hypertension (EH) is defined as a worldwide public health problem and one of the important risk factors for development of human coronary artery disease. Increased peripheral arterial resistance is one of the distinguishing characteristics of EH. The extracellular deposition of calcium in the arterial wall is defined as vascular calcification, which results in aortic stiffness and elevation of blood pressure. Regulation of vascular calcification is physiologically limited by γ-carboxylated proteins that regulate mineralization. Any deficiencies related to mineralization influence vascular calcification. As a result of vitamin-K deficiency or any problem associated with the vitamin K epOxide reductase complex subunit 1 (VKORC1) gene, Glu cannot be transformed to Gla and calcification initiates in blood vessels, myocardium, and cardiac.

OBJECTIVE

The aim of the study was to investigate the potential association of VKORC1 polymorphisms with the risk of EH.

MATERIALS AND METHODS

There were 100 individuals diagnosed with EH and 100 healthy individuals involved in the study. 3673G/A (rs9923231) and 9041G/A (rs7294) polymorphisms in the VKORC1 gene were determined by the PCR-restriction fragment length polymorphism method.

RESULTS

A significant difference was found between the rs7294 polymorphisms ratios of the case and control groups, but significant differences weren't found in distribution of the rs9923231 alleles. Finally it was determined that the GG genotype provides a 3.97-fold increased risk for EH compared to the AA genotype for the rs7294 polymorphism.

CONCLUSIONS

Our results suggest that the VKORC1 gene rs7294 polymorphism is important for the development of EH.

Calcium Signaling in Interstitial Cells: Focus on Telocytes

In this review, we describe the current knowledge on calcium signaling pathways in interstitial cells with a special focus on interstitial cells of Cajal (ICCs), interstitial Cajal-like cells (ICLCs), and telocytes. In detail, we present the generation of Ca²⁺ oscillations, the inositol triphosphate (IP₃)/Ca²⁺ signaling pathway and modulation exerted by cytokines and vasoactive agents on calcium signaling in interstitial cells. We discuss the physiology and alterations of calcium signaling in interstitial cells, and in particular in telocytes. We describe the physiological contribution of calcium signaling in interstitial cells to the pacemaking activity (e.g., intestinal, urinary, uterine or vascular pacemaking activity) and to the reproductive function. We also present the pathological contribution of calcium signaling in interstitial cells to the aortic valve calcification or intestinal inflammation. Moreover, we summarize the current knowledge of the role played by calcium signaling in telocytes in the uterine, cardiac and urinary physiology, and also in various pathologies, including immune response, uterine and cardiac pathologies.

Mitochondrial Ca²⁺ handling is crucial for generation of rhythmical Ca²⁺ waves in vascular interstitial cells from rabbit portal vein

Vasomotion is the rhythmical changes in vascular tone of various blood vessels. It was proposed that in rabbit portal vein (RPV) the spontaneous contractile activity is driven by vascular interstitial cells (VICs), since RPV VICs generate rhythmical changes in intracellular Ca(2+) concentration ([Ca(2+)]i) associated with membrane depolarisation in these cells. In this work, using confocal imaging in Fluo-3 loaded RPV VICs we studied if generation of rhythmical [Ca(2+)]i changes is affected when Ca(2+) handling by mitochondria is compromised. We also visualised mitochondria in VICs using Mito Tracker Green fluorescent dye. Our results showed that freshly dispersed RPV VICs generated rhythmical [Ca(2+)]i oscillations with a frequency of 0.2-0.01 Hz. Imaging of VICs stained with Mito Tracker Green revealed abundant mitochondria in these cells with a higher density of the organelles in sub-plasmalemmar region compared to the central region of the cell. Oligomycin, an ATP synthase inhibitor, did not affect the amplitude and frequency of rhythmical [Ca(2+)]i oscillations. In contrast, two uncoupling agents, carbonylcyanide-3-chlorophenylhydrazone (CCCP) and carbonylcyanide-4-trifluoromethoxyphenylhydrazone (FCCP) effectively abolished rhythmical [Ca(2+)]i changes with simultaneous increase in basal [Ca(2+)]i in RPV VICs. These data suggest that in RPV VICs mitochondrial Ca(2+) handling is important for the generation of rhythmical [Ca(2+)]i changes which underlie the spontaneous rhythmical contractile activity in this vessel.

Molecular identification of P2X receptors in vascular smooth muscle cells from rat anterior, posterior, and basilar arteries

BACKGROUND

Purinergic P2X receptors in vascular smooth muscle cells (VSMCs) play an important role in physiological stimulatory responses to the extracellularly released ATP. The aim of this work was to identify molecular P2X receptor subunits in VSMCs isolated from rat anterior, posterior and basilar arteries using a number of contemporary laboratory techniques.

METHODS

P2X mediated ionic currents were recorded using amphotericin B perforated patch clamp method. Gene expression analysis was performed using RT-PCR in manually collected VSMCs. The expression of proteins was confirmed by fluorescent immunocytochemistry.

RESULTS

Under voltage clamp conditions VSMCs stimulated by application of 10 μmol/l selective P2X receptor agonist αβ-meATP, the biphasic currents consisting of rapidly rising rapidly desensitizing and slowly desensitizing components were observed in freshly isolated myocytes from all three arteries. Using RT-PCR, the expression of genes encoding only P2X1 and P2X4 receptor subunits was detected in preparations from all three arteries. The expression of corresponding P2X1 and P2X4 receptor subunit proteins was confirmed in isolated VSMCs.

CONCLUSIONS

Our work therefore identified that in major arteries of rat cerebral circulation VSMCs express only P2X1 and P2X4 receptors subunits. We can propose that these P2X receptor subunits participate in functional P2X receptor structures mediating ATP-evoked stimulatory responses in cerebral vascular myocytes in vivo.

ATP-evoked sustained vasoconstrictions mediated by heteromeric P2X1/4 receptors in cerebral arteries

BACKGROUND AND PURPOSE

Current knowledge states that vasoconstrictor responses to ATP are mediated by rapidly desensitizing ligand-gated P2X1 receptors in vascular smooth muscle cells (VSMCs). However, ATP is implicated in contributing to pathological conditions involving sustained vasoconstrictor response such as cerebral vasospasm. The purpose of this study is to test the hypothesis that the stimulation of VSMC P2XR receptors (P2XRs) contributes to ATP-evoked sustained vasoconstrictions in rat middle cerebral arteries (RMCAs).

METHODS

Reverse transcription- polymerase chain reaction, Western blot, and immunocytochemistry were used to analyze expression of mRNA and proteins in RMCAs VSMCs. Ionic currents and calcium responses were investigated using patch-clamp and confocal imaging techniques, respectively. Functional responses were confirmed using wire myography.

RESULTS

Expression of mRNA and protein for P2X1R and P2X4R subunits was identified in RMCA VSMCs. Confocal imaging in fluo-3-loaded VSMCs showed that ATP and a selective P2XR agonist, αβmeATP, evoked similar dose-dependent increases in [Ca(2+)]i. Patch-clamp experiments identified 2 components of P2XR-mediated currents: consisting of a fast desensitizing phase mediated by homomeric P2X1Rs and a slowly desensitizing phase involving heteromeric P2X1/4Rs. Isometric tension measurements showed that ≈80%:20% of initial ATP-evoked vasoconstriction in RMCA is mediated by homomeric P2X1Rs and heteromeric P2X1/4Rs, respectively. The sustained slowly desensitizing and rapidly recovering from desensitization responses are mediated by heteromeric P2X1/4Rs.

CONCLUSIONS

This study reveals for the first time that apart from rapidly desensitizing homomeric P2X1Rs, heteromeric P2X1/4Rs contribute to the sustained component of the purinergic-mediated vasoconstriction in RMCA. Our study, therefore, identifies possible novel targets for therapeutical intervention in cerebral circulation.

Vascular smooth muscle cells from small human omental arteries express P2X1 and P2X4 receptor subunits

Stimulation of P2X receptors by ATP in vascular smooth muscle cells (VSMCs) is proposed to mediate vascular tone. However, understanding of P2X receptor-mediated actions in human blood vessels is limited, and therefore, the current work investigates the role of P2X receptors in freshly isolated small human gastro-omental arteries (HGOAs). Expression of P2X1 and P2X4 receptor subunit messenger RNA (mRNA) and protein was identified in individual HGOA VSMCs using RT-PCR and immunofluorescent analysis and using Western blot in multi-cellular preparations. ATP of 10 μmol/l and αβ-meATP of 10 μmol/l, a selective P2X receptor agonist, evoked robust increases in [Ca(2+)]i in fluo-3-loaded HGOA VSMCs. Pre-incubation with 1 μmol/l NF279, a selective P2X receptor antagonist, reduced the amplitude of αβ-meATP-induced increase in [Ca(2+)]i by about 70 %. ATP of 10 μmol/l and αβ-meATP of 10 μmol/l produced similar contractile responses in segments of HGOA, and these contractions were greatly reduced by 2 μmol/l NF449, a selective P2X receptor inhibitor. These data suggest that VSMCs from HGOA express P2X1 and P2X4 receptor subunits with homomeric P2X1 receptors likely serving as the predominant target for extracellular ATP.