Gender differences in microcirculation: observation using the hamster cheek pouch

An observational study of microcirculation among healthy individuals by age and sex

OBJECTIVE

This study measured normal ranges of microcirculatory parameters in healthy individuals and investigated differences in parameters by age and sex.

METHODS

Participants were enrolled into three groups with equal numbers of male and female: young (20-39 years), middle-aged (40-59 years), and elderly (60-79 years). Sublingual microcirculation images were obtained using the incident dark field (IDF).

RESULTS

A total of 75 female and 75 male healthy individuals were enrolled. The elderly group had a higher TVD (26.5 [2] vs. 25.2 [1.8]; p = 0.019) and a lower PPV (97 [2] vs. 98 [3]; p = 0.03) than did the young group. In the elderly group, systolic blood pressure (SBP) and mean arterial pressure (MAP) were moderately and positively correlated with MFI score (r = 0.407, p < 0.05, and r = 0.403, p < 0.05, respectively). The female participants had a lower MFI score than did the male participants (2.9 [2.8-3] vs. 3.0 [2.9-3]; p = 0.015).

CONCLUSIONS

This study revealed the range of microcirculatory parameters between different ages and sexes in healthy individuals. We found that blood pressure levels were correlated with microcirculatory parameters, especially in elders and female.

Sublingual microcirculation in healthy pediatric population using the sidestream dark-field imaging method

BACKGROUND

The sidestream dark-field imaging method is used to study microcirculation. Normal values of sublingual microcirculation parameters in healthy children of different age and gender categories are unknown.

OBJECTIVE

The study's main goal was to determine normal values of selected parameters of sublingual microcirculation in healthy children of different age and gender categories.

METHODS

40 healthy children were measured, ten aged 3-5.9 years, ten aged 6-10.9 years, ten aged 11-14.9 years, and ten aged 15-18.9 years. After recording the basic anthropometric parameters and vital functions, each volunteer had their microcirculation measured using an SDF probe placed sublingually. Three video clips were recorded and processed offline, and the three best and most stable parts of each were analyzed.

RESULTS

Total vascular density, small vessel density, proportion of perfused small vessels, perfused vessel density, perfused small vessel density, and DeBacker's score were significantly higher in females than in males. There were no differences between age groups in microcirculation parameters except MFI.

CONCLUSIONS

Age does not influence normal values of microcirculatory parameters. Female gender was associated with higher vessel density, perfused vessel density, and DeBacker's score. A suggestion of the normal range of microcirculatory parameters in healthy children is provided.

Sex differences in pressure and flow waveform physiology across the life course

Cardiovascular disease (CVD) has long been deemed a disease of old men. However, in 2019 CVD accounted for 35% of all deaths in women and, therefore, remains the leading cause of death in both men and women. There is increasing evidence to show that risk factors, pathophysiology and health outcomes related to CVD differ in women compared with men, yet CVD in women remains understudied, underdiagnosed and undertreated. Differences exist between the sexes in relation to the structure of the heart and vasculature, which translate into differences in blood pressure and flow waveform physiology. These physiological differences between women and men may represent an important explanatory factor contributing to the sex disparity in CVD presentation and outcomes but remain understudied. In this review we aim to describe sex differences in arterial pressure and flow waveform physiology and explore how they may contribute to differences in CVD in women compared to men. Given that unfavourable alterations in the cardiovascular structure and function can start as early as in utero, we report sex differences in waveform physiology across the entire life course.

In vitro endothelial hyperpermeability occurs early following traumatic hemorrhagic shock

BACKGROUND

Endothelial hyperpermeability is suggested to play a role in the development of microcirculatory perfusion disturbances and organ failure following hemorrhagic shock, but evidence is limited.

OBJECTIVE

To study the effect of plasma from traumatic hemorrhagic shock patients on in vitro endothelial barrier function.

METHODS

Plasma from traumatic hemorrhagic shock patients was obtained at the emergency department (ED), the intensive care unit (ICU), 24 h after ICU admission and from controls (n = 8). Sublingual microcirculatory perfusion was measured using incident dark field videomicroscopy at matching time points. Using electric cell-substrate impedance sensing, the effects of plasma exposure on in vitro endothelial barrier function of human endothelial cells were assessed.

RESULTS

Plasma from traumatic hemorrhagic shock patients collected at ED admission induced a 19% loss of in vitro endothelial resistance compared to plasma from controls (p < 0.001). This loss was due to reduced cell-cell contacts (p < 0.01). Plasma withdrawn at later time points did not affect endothelial barrier function (p > 0.99). Interestingly, in vitro endothelial resistance showed a positive association with in vivo microcirculatory perfusion (r = 0.56, p < 0.01).

CONCLUSIONS

Plasma from traumatic hemorrhagic shock patients obtained following ED admission, but not at later stages, induced in vitro endothelial hyperpermeability. This coincided with in vivo microcirculatory perfusion disturbances.

Sex-related differences in forearm skin microvascular reactivity of young healthy subjects

OBJECTIVE

To assess sex-related differences in forearm skin microvascular reactivity to vascular occlusion and cardiovascular health in young healthy women and men.

METHODS

203 young healthy individuals (67 men/136 women) participated in this study. Post-occlusive reactive hyperemia (PORH) in skin microcirculation following 1', 2' and 3' vascular occlusion period was assessed using laser Doppler flowmetry. Anthropometric parameters, body composition, blood pressure, heart rate and biochemical parameters were measured in all participants. Correlations between PORH and measured parameters were determined by using corresponding tests.

RESULTS

Women had significantly higher forearm PORH following 1', 2' and 3' vascular occlusion than men. Women had lower body mass index and waist-to-hip ratio, but higher fat mass than men. Men had significantly higher blood pressure and lower heart rate than women. Also, women had lower hemoglobin, urea, creatinine and serum uric acid, but higher HDL cholesterol level than men. PORH was negatively associated with waist-to-hip ratio and systolic blood pressure only in women.

CONCLUSIONS

Young healthy women exhibit higher skin microvascular reactivity to vascular occlusion compared to age-matched men. Increased systolic blood pressure or central obesity (waist-to-hip ratio) may pose greater risk to young healthy women than men by adversely affecting peripheral microvascular function.

Microcirculation After Trochanteric Femur Fractures: A Prospective Cohort Study Using Non-invasive Laser-Doppler Spectrophotometry

Proximal femur fractures represent a major healthcare problem in the aging society. High rates of post-operative infections are linked to risk factors that seem to affect local microcirculation. Patterns and time courses of alterations in microcirculation have, however, not been previously investigated. The aim of this prospective cohort study was to evaluate perioperative changes in microcirculation after trochanteric femur fractures using non-invasive laser-Doppler spectrophotometry to analyze how oxygen saturation (SO₂), hemoglobin content (Hb) and blood flow changed before and after surgery, and how these parameters were altered by implant type, gender, smoking, diabetes and age. Measurements were separately recorded for nine locations around the greater trochanter in 2, 8, and 15 mm depths, before surgery and 8, 24, 48 h, 4, 7, and 12 days after surgery in 48 patients. Three implants were compared: Dynamic Hip Screw, Gamma3 Nail, and Percutaneous Compression Plate. Surgery resulted in significant differences between the healthy and injured leg in SO₂, Hb and flow. Each parameter showed comparable values for both legs prior to surgery. Significantly higher values in SO₂ and flow were registered in women compared to men before and after surgery. Smoking caused significant increases in SO₂, Hb, and flow only in the superficial layer of the skin after surgery. Diabetes decreased blood flow at 2 and 8 mm depth and increased SO₂ at 8 and 15 mm depth after surgery. Age revealed a significant negative correlation with flow. The ability to increase the flow rate after surgery decreased with age. Comparison of implants indicated the minimally invasive implant PCCP altered microcirculation less than the DHS or the Gamma3 nail. Overall, the proximal femur fracture alone did not alter local skin microcirculation significantly in a way comparable to the effect caused by surgery. In conclusion, microcirculation after proximal femur fractures is highly affected by surgery, gender, smoking, diabetes, age and implant in ways specified in this study.

Functional characterization of collaterals in the human gingiva by laser speckle contrast imaging

OBJECTIVE

The rate of blood flow between the various areas of the gingiva in resting position and under challenge is unknown. In this study, the LSCI method was used to map spatial and temporal changes in gingival blood flow after transient compression.

METHODS

Horizontal, vertical, and papilla base compressions were applied on the attached gingiva in 21 healthy patients (13 women, 8 men). LSCI was used to determine dynamic changes in regional blood flow during a five-second occlusion interval and subsequent reperfusion for twenty minutes.

RESULTS

Resting blood flow in the attached gingiva apical to the papillae was higher as compared to that in the midbuccal area of the teeth. During short-term horizontal compression, ischemia was greater coronal than apical to the occlusion line. Postocclusive hyperemia was observed not only in the regions affected by ischemia but encompassed a wider area. Hyperemic response was more pronounced and prolonged in male than in female patients.

CONCLUSIONS

Blood flow in the attached gingiva shows spatial differences. Our findings corroborate the apicocoronal orientation of blood circulation. Periodontal and papillary collaterals may have little role in the blood supply of the adjacent attached gingiva under physiological conditions.

Sex differences influencing micro- and macrovascular endothelial phenotype in vitro

KEY POINTS

Endothelial dysfunction is an early hallmark of multiple disease states that also display sex differences with respect to age of onset, frequency and severity. Results of in vivo studies of basal and stimulated microvascular barrier function revealed sex differences that are difficult to ascribe to specific cells or environmental factors. The present study evaluated endothelial cells (EC) isolated from macro- and/or microvessels of reproductively mature rats under the controlled conditions of low-passage culture aiming to test the assumption that EC phenotype would be sex independent. The primary finding was that EC, regardless of where they are derived, retain a sex-bias in low-passage culture, independent of varying levels of reproductive hormones. The implications of the present study include the fallacy of expecting a universal set of mechanisms derived from study of EC from one sex and/or one vascular origin to apply uniformly to all EC under unstimulated conditions, and no less in disease.

ABSTRACT

Vascular endothelial cells (EC) are heterogeneous with respect to phenotype, reflecting at least the organ of origin, location within the vascular network and physical forces. As an independent influence on EC functions in health or aetiology, susceptibility, and progression of dysfunction in numerous disease states, sex has been largely ignored. The present study focussed on EC isolated from aorta (macrovascular) and skeletal muscle vessels (microvascular) of age-matched male and female rats under identical conditions of short-term (passage 4) culture. We tested the hypothesis that genomic sex would not influence endothelial growth, wound healing, morphology, lactate production, or messenger RNA and protein expression of key proteins (sex hormone receptors for androgen and oestrogens α and β; platelet endothelial cell adhesion molecule-1 and vascular endothelial cadherin mediating barrier function; α_v β₃ and N-cadherin influencing matrix interactions; intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 mediating EC/white cell adhesion). The hypothesis was rejected because the EC origin (macro- vs. microvessel) and sex influenced multiple phenotypic characteristics. Statistical model analysis of EC growth demonstrated an hierarchy of variable importance, recapitulated for other phenotypic characteristics, with predictions assuming EC homogeneity < sex < vessel origin < sex and vessel origin. Furthermore, patterns of EC mRNA expression by vessel origin and by sex did not predict protein expression. Overall, the present study demonstrated that accurate assessment of sex-linked EC dysfunction first requires an understanding of EC function by position in the vascular tree and by sex. The results from a single EC tissue source/species/sex cannot provide universal insight into the mechanisms regulating in vivo endothelial function in health, and no less in disease.

Sex-Specific Characteristics of the Microcirculation

The requirements of metabolizing tissue are both continuous and variable; accordingly, the microvasculature serving that tissue must be similarly dynamic. Just as it is recognized that males and females of the same species have differing metabolic requirements, is it not likely that the microvasculature serving these tissues will differ by sex? This section focusing on the constituents of the microcirculation identifies what is known presently about the role sex plays in matching metabolic demand with microvascular function and areas requiring additional study. Many of the identified sex differences are subtle and easily ignored. In the aggregate, though, they can profoundly alter phenotype, especially under stressful conditions including pregnancy, exercise, and disease states ranging from diabetes to heart failure. Although the features presently identified to "have sex" range from differences in growth, morphology, protein expression, and intracellular signaling, males and females alike achieve homeostasis, likely by different means. Studies of microvascular sexual dimorphism are also identifying age as an independent but interacting factor requiring additional attention. Overall, attempting to ignore either sex and/or age is inappropriate and will prevent the design and implementation of appropriate interventions to present, ameliorate, or correct microvascular dysfunction.

Cardiovascular and autoimmune diseases in females: The role of microvasculature and dysfunctional endothelium

Cardiovascular (CV) diseases are becoming increasingly frequent and associated with a high incidence of CV events, disability and death. It is known that there is a relationship between CV burden and systemic autoimmune diseases (SADs) that is mainly due to inflammation and autoimmunity, but the other mechanisms underlying the high CV risk of SAD patients have not yet been fully clarified. The aim of this review article is to discuss some of the specific factors associated with the accelerated atherosclerosis (ATS) characterising SADs (female sex, the microcirculation and the endothelium) in order to highlight the importance of an early diagnosis and the prompt implementation of preventive measures, as well as the possible role of new therapeutic strategies such as vaccine immunomodulation. Finally, as the natural history of ATS begins with endothelial injury (a potentially reversible process that is influenced by various factors) and microvascular damage plays a central role in the etiopathogenesis of SADs, it underlines the crucial need for the development of reliable means of detecting sub-clinical abnormalities in the microcirculation, particularly coronary microcirculation dysfunction.