Vascular Smooth Muscle Cells Mechanosensitive Regulators and Vascular Remodeling

Blood vessels are subjected to mechanical loads of pressure and flow, inducing smooth muscle circumferential and endothelial shear stresses. The perception and response of vascular tissue and living cells to these stresses and the microenvironment they are exposed to are critical to their function and survival. These mechanical stimuli not only cause morphological changes in cells and vessel walls but also can interfere with biochemical homeostasis, leading to vascular remodeling and dysfunction. However, the mechanisms underlying how these stimuli affect tissue and cellular function, including mechanical stimulation-induced biochemical signaling and mechanical transduction that relies on cytoskeletal integrity, are unclear. This review focuses on signaling pathways that regulate multiple biochemical processes in vascular mesangial smooth muscle cells in response to circumferential stress and are involved in mechanosensitive regulatory molecules in response to mechanotransduction, including ion channels, membrane receptors, integrins, cytoskeletal proteins, nuclear structures, and cascades. Mechanoactivation of these signaling pathways is closely associated with vascular remodeling in physiological or pathophysiological states.

Recombinant Human Soluble Thrombomodulin Suppresses Arteritis in a Mouse Model of Kawasaki Disease

<b><i>Introduction and Objective:</i></b> Kawasaki disease (KD) is associated with diffuse and systemic vasculitis of unknown aetiology and primarily affects infants and children. Intravenous immunoglobulin (IVIG) treatment reduces the risk of developing coronary aneurysms, but some children have IVIG-resistant KD, which increases their risk of developing coronary artery injury. Here, we investigated the effect of recombinant human soluble thrombomodulin (rTM), which has anticoagulant, anti-inflammatory, and cytoprotective properties on the development of coronary arteritis in a mouse model of vasculitis. <b><i>Methods:</i></b> An animal model of KD-like vasculitis was created by injecting mice with <i>Candida albicans</i> water-soluble fraction (CAWS). This model was used to investigate the mRNA expression of interleukin (IL)-10, tumour necrosis factor alpha (TNF-α), and tissue factor (TF), in addition to histopathology of heart tissues. <b><i>Results:</i></b> rTM treatment significantly reduces cardiac vascular endothelium hypertrophy by 34 days after CAWS treatment. In addition, mRNA expression analysis revealed that rTM administration increased cardiac IL-10 expression until day 27, whereas expression of TNF-α was unaffected. Moreover, in the spleen, rTM treatment restores IL-10 and TF expression to normal levels. <b><i>Conclusion:</i></b> These findings suggest that rTM suppresses CAWS-induced vasculitis by upregulating IL-10. Therefore, rTM may be an effective treatment for KD.

Effects of Fluid Therapy on Mesenteric Microcirculation Using New Probe-Based Confocal Laser Endomicroscopy (Cellvizio®) in a Porcine Model of Endotoxic Shock

<b><i>Background:</i></b> Microcirculatory alterations have been observed at the early phase of sepsis, although macrocirculation seems preserved. The aim of this study was to analyze the effect of crystalloid fluid therapy on mesenteric microcirculation, assessed by using the confocal laser endomicroscope Cellvizio®, in an endotoxic porcine model. <b><i>Methods:</i></b> It is a prospective endotoxic shock (lipopolysaccharide infusion) experimental trial. Piglets were divided into 3 groups: 6 in the sham group (no LPS injection, no fluid), 9 in the control group (LPS infusion, no fluid), and 6 in the crystalloids group (LPS infusion and fluid resuscitation with crystalloids). Fluid resuscitation consisted in a fluid bolus of 20 mL/kg 0.9% saline over 30 min followed by a 10 mL/kg/h fluid rate over 4 h. Mesenteric microcirculation was assessed using a confocal laser endomicroscope (Cellvizio®). Blood flow within capillaries was visually assessed according to the point of care microcirculation (POEM) score. <b><i>Results:</i></b> At baseline, the 3 groups were similar regarding hemodynamic, biological, and microcirculatory parameters. At T360, the POEM score significantly decreased in the control and crystalloids groups, whereas it remained unchanged in the sham group (respectively, 1.62 ± 1.06, 1.2 ± 0.45, and 5.0 ± 0, <i>p</i> = 0.011). There was no significant difference in cardiac output at T360 between the sham and crystalloids groups (3.1 ± 0.8 vs. 2.3 ± 0.6, <i>p</i> = 0.132) or between the control and crystalloids groups (2.0 ± 0.6 vs. 2.3 ± 0.6, <i>p</i> = 0.90). <b><i>Conclusion:</i></b> There was no significant improvement of microcirculatory alterations after crystalloids resuscitation despite improvement in macrocirculatory parameters in early experimental sepsis.

Characterizing Tissue Remodeling and Mechanical Heterogeneity in Cerebral Aneurysms

Accurately assessing the complex tissue mechanics of cerebral aneurysms (CAs) is critical for elucidating how CAs grow and whether that growth will lead to rupture. The factors that have been implicated in CA progression – blood flow dynamics, immune infiltration, and extracellular matrix remodeling – all occur heterogeneously throughout the CA. Thus, it stands to reason that the mechanical properties of CAs are also spatially heterogeneous. Here, we present a new method for characterizing the mechanical heterogeneity of human CAs using generalized anisotropic inverse mechanics, which uses biaxial stretching experiments and inverse analyses to determine the local Kelvin moduli and principal alignments within the tissue. Using this approach, we find that there is significant mechanical heterogeneity within a single acquired human CA. These results were confirmed using second harmonic generation imaging of the CA’s fiber architecture and a correlation was observed. This approach provides a single-step method for determining the complex heterogeneous mechanics of CAs, which has important implications for future identification of metrics that can improve accuracy in prediction risk of rupture.

Quantification of Lipid Area within Thermogenic Mouse Perivascular Adipose Tissue Using Standardized Image Analysis in FIJI

Quantification of adipocyte size and number is routinely performed for white adipose tissues using existing image analysis software. However, thermogenic adipose tissue has multilocular adipocytes, making it difficult to distinguish adipocyte cell borders and to analyze lipid proportion using existing methods. We developed a simple, standardized method to quantify lipid content of mouse thermogenic adipose tissue. This method, using FIJI analysis of hematoxylin/eosin stained sections, was highly objective and highly reproducible, with ∼99% inter-rater reliability. The method was compared to direct lipid staining of adipose tissue, with comparable results. We used our method to analyze perivascular adipose tissue (PVAT) from C57BL/6 mice on a normal chow diet, compared to calorie restriction or a high fat diet, where lipid storage phenotypes are known. Results indicate that lipid content can be estimated within mouse PVAT in a quantitative and reproducible manner, and shows correlation with previously studied molecular and physiological measures.

The Impact of Fitness Status on Vascular and Baroreceptor Function in Healthy Women and Men

<b><i>Background:</i></b> Chronic endurance exercise training elicits desirable physiological adaptations in the cardiovascular system. The volume of exercise training required to generate healthy adaptations is unclear. This study assessed the effects of differing exercise training levels on arterial stiffness, compliance, and autonomic function. <b><i>Methods:</i></b> Eighty healthy adults (38.5 ± 9.7 years; 44% female) defined as endurance-trained (ET, <i>n</i> = 29), normally active (NA, <i>n</i> = 27), or inactive (IN, <i>n</i> = 24) participated. Cardiovascular markers, including hemodynamics, large arterial compliance and small arterial compliance (LAC and SAC), carotid-femoral pulse wave velocity (PWV), and spontaneous baroreceptor sensitivity (BRS) were assessed. <b><i>Results:</i></b> ET showed significantly greater LAC values (21.4 ± 6.5) than NA (16.9 ± 2.5; <i>p</i> = 0.002) and IN (14.7 ± 3.2 mL × mm Hg × 10; <i>p</i> = 0.028). Values for SAC and BRS were significantly higher in ET than IN (<i>p</i> &#x3c; 0.001 and <i>p</i> = 0.028, respectively), but not NA. Compared to IN, PWV values for ET and NA were significantly lower (<i>p</i> &#x3c; 0.003). After adjusting for covariates (age, sex, and SBP), significant associations with cardiovascular fitness status were noted for all markers but BRS. <b><i>Conclusion:</i></b> Endurance exercise increases LAC likely due to high-volume training; however, lower volumes of physical activity may be sufficient to positively benefit vascular health overall.

Microstructural Characterization of Resistance Artery Remodelling in Diabetes Mellitus

<b><i>Introduction:</i></b> Microvascular remodelling is a symptom of cardiovascular disease. Despite the mechanical environment being recognized as a major contributor to the remodelling process, it is currently only understood in a rudimentary way. <b><i>Objective:</i></b> A morphological and mechanical evaluation of the resistance vasculature in health and diabetes mellitus. <b><i>Methods:</i></b> The cells and extracellular matrix of human subcutaneous resistance arteries from abdominal fat biopsies were imaged using two-photon fluorescence and second harmonic generation at varying transmural pressure. The results informed a two-layer mechanical model. <b><i>Results:</i></b> Diabetic resistance arteries reduced in wall area as pressure was increased. This was attributed to the presence of thick, straight collagen fibre bundles that braced the outer wall. The abnormal mechanical environment caused the internal elastic lamina and endothelial and vascular smooth muscle cell arrangements to twist. <b><i>Conclusions:</i></b> Our results suggest diabetic microvascular remodelling is likely to be stress-driven, comprising at least 2 stages: (1) Laying down of adventitial bracing fibres that limit outward distension, and (2) Deposition of additional collagen in the media, likely due to the significantly altered mechanical environment. This work represents a step towards elucidating the local stress environment of cells, which is crucial to build accurate models of mechanotransduction in disease.

Opioids Cause Sex-Specific Vascular Changes via Cofilin-Extracellular Signal-Regulated Kinase Signaling: Female Mice Present Higher Risk of Developing Morphine-Induced Vascular Dysfunction than Male Mice

Recent studies have shown that chronic use of prescription or illicit opioids leads to an increased risk of cardiovascular events and pulmonary arterial hypertension. Indices of vascular age and arterial stiffness are also shown to be increased in opioid-dependent patients, with the effects being more marked in women. There are currently no studies investigating sex-specific vascular dysfunction in opioid use, and the mechanisms leading to opioid-induced vascular damage remain unknown. We hypothesized that exposure to exogenous opioids causes sex-specific vascular remodeling that will be more pronounced in female. Acknowledging the emerging roles of cofilins and extracellular signal-regulated kinases (ERKs) in mediating actin dynamics, we investigated the effects of morphine on these molecules. Twenty-four hour exposure to morphine increased inactivated cofilin and activated ERKs in resistance arteries from female mice, which may promote stress fiber over-assembly. We also performed continuous intraluminal infusion of morphine in pressurized resistance arteries from male and female mice using culture pressure myographs. We observed that morphine reduced the vascular diameter in resistance arteries from female, but not male mice. These results have significant implications for the previously unexplored role of exogenous opioids as a modifiable cardiovascular risk factor, especially in women.

DNA Methylation Profile of the SREBF2 Gene in Human Fetal Aortas

Increasing evidence suggests that maternal cholesterol represents an important risk factor for atherosclerotic disease in offspring already during pregnancy, although the underlying mechanisms have not yet been elucidated. Eighteen human fetal aorta samples were collected from the spontaneously aborted fetuses of normal cholesterolemic and hypercholesterolemic mothers. Maternal total cholesterol levels were assessed during hospitalization. DNA methylation profiling of the whole <i>SREBF2</i> gene CpG island was performed (<i>p</i> value &#x3c;0.05). The Mann-Whitney U test was used for comparison between the 2 groups. For the first time, our study revealed that in fetal aortas obtained from hypercholesterolemic mothers, the <i>SREBF2</i> gene shows 4 significant differentially hypermethylated sites in the 5′UTR-CpG island. This finding indicates that more effective long-term primary cardiovascular prevention programs need to be designed for the offspring of mothers with hypercholesterolemia. Further studies should be conducted to clarify the epigenetic mechanisms underlying the association between early atherogenesis and maternal hypercholesterolemia during pregnancy.

Microvessel Density: Integrating Sex-Based Differences and Elevated Cardiovascular Risks in Metabolic Syndrome

Metabolic syndrome (MetS) is a complex pathological state consisting of metabolic risk factors such as hypertension, insulin resistance, and obesity. The interconnectivity of cellular pathways within various biological systems suggests that each individual component of MetS may share common pathological sources. Additionally, MetS is closely associated with vasculopathy, including a reduction in microvessel density (MVD) (rarefaction) and elevated risk for various cardiovascular diseases. Microvascular impairments may contribute to perfusion-demand mismatch, where local metabolic needs are insufficiently met due to the lack of nutrient and oxygen supply, thus creating pathological positive-feedback loops and furthering the progression of disease. Sexual dimorphism is evident in these underlying cellular mechanisms, which places males and females at different levels of risk for cardiovascular disease and acute ischemic events. Estrogen exhibits protective effects on the endothelium of pre-menopausal women, while androgens may be antagonistic to cardiovascular health. This review examines MetS and its influences on MVD, as well as sex differences relating to the components of MetS and cardiovascular risk profiles. Finally, translational relevance and interventions are discussed in the context of these sex-based differences.