Investigation on the influence of the skin tone on hyperspectral imaging for free flap surgery

Hyperspectral imaging (HSI) is a new emerging modality useful for the noncontact assessment of free flap perfusion. This measurement technique relies on the optical properties within the tissue. Since the optical properties of hemoglobin (Hb) and melanin overlap, the results of the perfusion assessment and other tissue-specific parameters are likely to be distorted by the melanin, especially at higher melanin concentrations. Many spectroscopic devices have been shown to struggle with a melanin related bias, which results in a clinical need to improve non-invasive perfusion assessment, especially for a more pigmented population. This study investigated the influence of skin tones on tissue indices measurements using HSI. In addition, other factors that might affect HSI, such as age, body mass index (BMI), sex or smoking habits, were also considered. Therefore, a prospective feasibility study was conducted, including 101 volunteers from whom tissue indices measurements were performed on 16 different body sites. Skin tone classification was performed using the Fitzpatrick skin type classification questionnaire, and the individual typology angle (ITA) acquired from the RGB images was calculated simultaneously with the measurements. Tissue indices provided by the used HSI-device were correlated to the possible influencing factors. The results show that a dark skin tone and, therefore, higher levels of pigmentation influence the HSI-derived tissue indices. In addition, possible physiological factors influencing the HSI-measurements were found. In conclusion, the HSI-based tissue indices can be used for perfusion assessment for people with lighter skin tone levels but show limitations in people with darker skin tones. Furthermore, it could be used for a more individual perfusion assessment if different physiological influencing factors are respected.

Spectral changes in skin blood flow during pressure manipulations or sympathetic stimulation

Skin blood flow is commonly determined by laser Doppler flowmetry (LDF). It has been suggested that pathophysiological conditions can be assessed by analysis of specific frequency domains of the LDF signals. We tested whether physiological stimuli that activate myogenic and neurogenic mechanisms would affect relevant portions of the laser Doppler spectrum. LDF sensors were placed on the right forearm of 14 healthy volunteers for myogenic (six females) and 13 for neurogenic challenge (five females). Myogenic responses were tested by positioning the arm ∼50° above/below heart level. Neurogenic responses were tested by immersing the left hand into an ice slurry with and without topical application of local anaesthetic. Short-time Fourier analyses were computed over the range of 0.06 to 0.15 Hz for myogenic and 0.02 to 0.06 Hz for neurogenic. No significant differences in spectral density were observed (P = 0.40) in the myogenic range with arm above (7 ± 54 × 10-4 dB) and below heart (7 ± 14 × 10-4 dB). Neurogenic spectral density showed no significant increase from baseline to cold pressor test (0.0017 ± 0.0013 and 0.0038 ± 0.0039 dB; P = 0.087, effect size 0.47). After application of anaesthetic, neurogenic spectral density was unchanged between the baseline and cold pressor test (0.0014 ± 0.0025 and 0.0006 ± 0.0005 dB; P = 0.173). These results suggest that changes in the myogenic and neurogenic spectral density of LDF signals did not fully reflect the skin vascular function activated by pressure manipulation and sympathetic stimulation. Therefore, LDF myogenic and neurogenic spectral density data should be interpreted with caution.

Mucopolysaccharide polysulfate increases local skin blood volume through nitric oxide production

BACKGROUND

Mucopolysaccharide polysulfate (MPS) is widely used as an active ingredient in topical preparations for the treatment of asteatosis and blood flow disorders. Although topical MPS products can increase cutaneous blood flow (CBF), the underlying mechanism remains unclear.

OBJECTIVE

In this study, we aimed to elucidate how MPS increases CBF. We investigated the association of nitric oxide (NO), a powerful mediator associated with increased local blood volume, with the blood flow-accelerating action of MPS in mice. In addition, we verified the effects of MPS on NO production in different skin cell types, such as keratinocytes (KCs), endothelial cells (ECs), and dermal fibroblasts (DFs).

METHODS

We used raster-scanning optoacoustic imaging mesoscopy to observe in vivo changes in the skin blood volume. NO production was determined in each cell using an NO indicator. An enzyme-linked immunoassay was used to measure the phosphorylated nitric oxide synthase (NOS) levels in ECs, DFs, and KCs in the presence or absence of MPS.

RESULTS

Topical application of MPS increased the skin blood volume in mice, and this increase was abolished through the addition of NOS inhibitors. MPS promoted the dose-dependent production of NO in various cells, which caused alterations in the phosphorylation state of NOS.

CONCLUSION

Our findings demonstrate that MPS promotes an increase in skin blood volume and NO production in various skin cell types. These results suggest that MPS can potentially accelerate CBF through the NO biosynthesis pathway in different skin cell types.

Caliper, contrast enhanced-ultrasound or laser speckle contrast imaging: Techniques to follow mice melanoma growth

Due to morphological characteristics, metastatic melanoma is a cancer for which vascularization is not a diagnostic criterion. Laser speckle contrast imaging (LSCI) and contrast enhanced ultrasound (CEUS) are two imaging techniques that will be explored in this study, which aims to confirm these two techniques for monitoring tumor vascularization. B16F10 cells were xenografted to C57BL/6 mice treated with anti-PD1 or 0.9% NaCl. Tumor volume was measured daily while CEUS and LSCI were performed weekly. LSCI and CEUS analyses showed a decrease in tumor perfusion in both groups of mice. Although both CEUS and LSCI are useful for measuring tumor volume, LSCI appears to be more robust and effective for monitoring tumor microcirculation. Non-invasive investigations are needed to better predict tumor vascularization: CEUS and LSCI have a good applicability in a mice model.

Microvascular dysfunction in women with a history of hypertensive disorders of pregnancy: A population-based retrospective cohort study

OBJECTIVE

To evaluate microvascular function in women with previous hypertensive disorders of pregnancy (HDP).

DESIGN

Retrospective population-based cohort study.

SETTING

Linköping, Sweden.

POPULATION

Women aged 50-65 years, participating in the Swedish CArdioPulmonary bioImage Study (SCAPIS) at one site (Linköping) 2016-18, who underwent microcirculatory assessment (N = 1222).

METHODS

Forearm skin comprehensive microcirculatory assessment was performed with a PeriFlux PF6000 EPOS (Enhanced Perfusion and Oxygen Saturation) system measuring oxygen saturation and total speed resolved perfusion. Obstetric records were reviewed to identify women with previous HDP. Data on cardiovascular risk factors, comorbidities, medication, lifestyle, anthropometric data, and biochemical analyses were obtained from SCAPIS. The microcirculatory data were compared between women with and without previous HDP.

MAIN OUTCOME MEASURES

Skin microcirculatory oxygen saturation and total speed resolved perfusion at baseline and post-ischaemic peak.

RESULTS

Women with previous pre-eclampsia displayed impaired post-ischaemic peak oxygen saturation compared with women with normotensive pregnancies (88%, interquartile range [IQR] 84-89% vs 91%, IQR 87-94%, p = 0.001) 6-30 years after pregnancy. The difference remained after multivariable adjustment (β -2.69, 95% CI -4.93 to -0.45).

CONCLUSIONS

The findings reveal microvascular dysfunction at long-term follow up in women with previous pre-eclampsia and strengthen the possible role of endothelial dysfunction as a link to the increased risk of cardiovascular disease in women with HDP.

Lower-Limb Perfusion and Cardiovascular Physiology Are Significantly Improved in Non-Healthy Aged Adults by Regular Home-Based Physical Activities-An Exploratory Study

Common daily activities including walking might be used to improve cardiovascular health in the presence of disease. Thus, we designed a specific home-based physical activity program to assess cardiovascular indicators in an older, non-active, non-healthy population. Ten participants, with a mean age of 62.4 ± 5.6 years old, were chosen and evaluated twice-upon inclusion (D0), and on day 30 (D30)-following program application. Perfusion was measured in both feet by laser Doppler flowmetry (LDF) and by polarised spectroscopy (PSp). Measurements were taken at baseline (Phase 1) immediately after performing the selected activities (Phase 2) and during recovery (Phase 3). Comparison outcomes between D0 and D30 revealed relevant differences in Phase 1 recordings, namely a significant increase in LDF perfusion (p = 0.005) and a significant decrease in systolic blood pressure (p = 0.008) and mean arterial pressure (MAP) (p = 0.037). A correlation between the increase in perfusion and the weekly activity time was found (p = 0.043). No differences were found in Phase 2, but, in Phase 3, LDF values were still significantly higher in D30 compared with D0. These simple activities, regularly executed with minimal supervision, significantly improved the lower-limb perfusion while reducing participants' systolic pressure and MAP, taken as an important improvement in their cardiovascular status.

α-Catenin promotes dermal fibroblasts proliferation and migration during wound healing via FAK/YAP activation

Skin wound healing is a complex and organized biological process, and the dermal fibroblasts play a crucial role. α-Catenin is known to be involved in regulating various cellular signals, and its role in wound healing remains unclear. Here, we have identified the pivotal role of the α-catenin/FAK/YAP signaling axis in the proliferation and migration of dermal fibroblasts, which contributes to the process of skin wound healing. Briefly, when α-catenin was knocked down specifically in dermal fibroblasts, the wound healing rate is significantly delayed. Moreover, interfering with α-catenin can impede the proliferation and migration of dermal fibroblasts both in vitro and in vivo. Mechanistically, the overexpression of α-catenin upregulates the nuclear accumulation of YAP and transcription of downstream target genes, resulting in enhanced the proliferation and migration of dermal fibroblasts. Furthermore, the FAK Tyr397 phosphorylation inhibitor blocked the promoting effects of α-catenin on YAP activation. Importantly, the continuous phosphorylation mutation of FAK Tyr397 reversed the retardatory effects of α-catenin knockdown on wound healing, by increasing the vitality of fibroblasts. Likewise, α-catenin/FAK was validated as a therapeutic target for wound healing in the db/db chronic trauma model. In summary, our findings have revealed a novel mechanism by which α-catenin facilitates the function of fibroblasts through the activity of the FAK/YAP signaling axis. These findings define a promising therapeutic strategy for accelerating the wound healing process.

Studying Erythromelalgia Using Doppler Flowmetry Perfusion Signals and Wavelet Analysis-An Exploratory Study

Erythromelalgia (EM) is a rare disease, which is still poorly characterized. In the present paper, we compared the hand perfusion of one female EM patient, under challenges, with a healthy control group. Using a laser Doppler flowmeter (LDF) with an integrated thermal probe, measurements were taken in both hands at rest (Phase I) and after two separate challenges-post-occlusive hyperemia (PORH) in one arm (A) and reduction of skin temperature (cooling) with ice in one hand (B) (Phase II). The final measurement periods corresponded to recovery (Phases III and IV). The control group involved ten healthy women (27.3 ± 7.9 years old). A second set of measurements was taken in the EM patient one month after beginning a new therapeutic approach with beta-blockers (6.25 mg carvedilol twice daily). Z-scores of the patient's LDF and temperature fluctuations compared to the control group were assessed using the Wavelet transform (WT) analysis. Here, fluctuations with |Z| > 1.96 were considered significantly different from healthy values, whereas positive or negative Z values indicated higher or lower deviations from the control mean values. Cooling elicited more measurable changes in LDF and temperature fluctuations, especially in higher frequency components (cardiac, respiratory, and myogenic), whereas PORH notably evoked changes in lower frequency components (myogenic, autonomic, and endothelial). No significant Z-score deviations were observed in the second measurement, which might signify a stabilization of the patient's distal perfusion following the new therapeutic approach. This analysis involving one EM patient, while clearly exploratory, has shown significant deviations in WT-derived physiological components' values in comparison with the healthy group, confirming the interest in using cold temperature as a challenger. The apparent agreement achieved with the clinical evaluation opens the possibility of expanding this approach to other patients and pathologies in vascular medicine.

Self-Assembled and Multilayer-Overlapped ESM-PDA@rGO Nanofilm-Based Flexible Wearable Sensor for Real-Time Body Temperature Monitoring

There is an urgent need for wearable sensors that continuously monitor human physiological conditions in real time. Herein, an ESM-PDA@rGO-based flexible wearable temperature sensor was successfully constructed by integrating an eggshell membrane (ESM) with reduced graphene oxide (rGO) through dopamine (DA) polymerization. Depending on the "bridge effect" of diversified polydopamine (PDA) chains, on the one hand, a staggered arrangement of PDA-rGO frameworks and a lot of conductive pathways were produced and acted as an active layer. On the other hand, PDA-rGO frameworks were linked with ESM by PDA chains as a flexible sensing nanofilm. As a result, these mechanical merits of the ESM-PDA@rGO exhibited a 1.8-fold increase in Young' s modulus and 1.4-fold increase in tensile strength. Thereby, the conformability and performance of the temperature sensor were greatly enhanced, showing excellent sensitivity (-2.23%/°C), good linearity (R2 = 0.979), as well as stability. Especially, the flexible sensing nanofilm is evolved from the staggered arrangement of PDA-rGO frameworks, which endows it with rapid response (only 4-8 s), high resolution (0.1 °C), as well as excellent long-term durability (10 weeks). More importantly, the temperature sensor demonstrates insensitivity to bending deformation, ensuring reliable wearing stability. The sensor allows for online, real-time monitoring of human body temperature, encompassing both core (forehead, temple, cochlea, and exhale gas) and shell (palm and back of the hand, fingertip, and instep) temperatures. Particularly, it can accurately assess minor changes in peripheral body temperature before and after exercise, and it is capable of mapping daily patterns of body temperatures. The developed temperature sensor will provide us new materials design concepts and holds considerable promise in the fields of e-skin, disease surveillance, prediction, and diagnose.

Diabetic microvascular disease in non-classical beds: the hidden impact beyond the retina, the kidney, and the peripheral nerves

Diabetes microangiopathy, a hallmark complication of diabetes, is characterised by structural and functional abnormalities within the intricate network of microvessels beyond well-known and documented target organs, i.e., the retina, kidney, and peripheral nerves. Indeed, an intact microvascular bed is crucial for preserving each organ's specific functions and achieving physiological balance to meet their respective metabolic demands. Therefore, diabetes-related microvascular dysfunction leads to widespread multiorgan consequences in still-overlooked non-traditional target organs such as the brain, the lung, the bone tissue, the skin, the arterial wall, the heart, or the musculoskeletal system. All these organs are vulnerable to the physiopathological mechanisms that cause microvascular damage in diabetes (i.e., hyperglycaemia-induced oxidative stress, inflammation, and endothelial dysfunction) and collectively contribute to abnormalities in the microvessels' structure and function, compromising blood flow and tissue perfusion. However, the microcirculatory networks differ between organs due to variations in haemodynamic, vascular architecture, and affected cells, resulting in a spectrum of clinical presentations. The aim of this review is to focus on the multifaceted nature of microvascular impairment in diabetes through available evidence of specific consequences in often overlooked organs. A better understanding of diabetes microangiopathy in non-target organs provides a broader perspective on the systemic nature of the disease, underscoring the importance of recognising the comprehensive range of complications beyond the classic target sites.

Aging is associated with impaired triggering of TRPV3-mediated cutaneous vasodilation: a crucial process for local heat exposure

Sensing temperature is vitally important to adapt our body to environmental changes. Local warm detection is required to initiate regulation of cutaneous blood flow, which is part of the peripheral thermoregulatory mechanisms, and thus avoid damage to surrounding tissues. The mechanisms mediating cutaneous vasodilation during local heat stress are impaired with aging. However, the impact of aging on the ability of the skin to detect subtle thermal changes is unknown. Among heat-activated cation channels, transient receptor potential vanilloid 3 (TRPV3) is a thermo-sensor predominantly expressed on keratinocytes and involved in local vascular thermoregulatory mechanisms of the skin in young mice. In the present study, using a murine in vivo model of local heat exposure of the skin, we showed that heat-induced vasodilation was reduced in old mice associated with reduced expression of TRPV3 channels. We also found a decrease in expression and activity of TRPV3 channel, as well as reduced TRPV3-dependent adenosine tri-phosphate release in human primary keratinocytes from old donors. This study shows that aging alters the epidermal TRPV3 channels, which might delay the detection of changes in skin temperature, thereby limiting the mechanisms triggered for local vascular thermoregulation in the old skin.

Transfusion increased skin blood flow when initially low in volume-resuscitated patients without acute bleeding

Background

Alterations in skin blood flow is a marker of inadequate tissue perfusion in critically ill patients after initial resuscitation. The effects of red blood cell transfusions (RBCT) on skin perfusion are not described in this setting. We evaluated the effects of red blood cell transfusions on skin tissue perfusion in critically ill patients without acute bleeding after initial resuscitation.

Methods

A prospective observational study included 175 non-bleeding adult patients after fluid resuscitation requiring red blood cell transfusions. Using laser Doppler, we measured finger skin blood flow (SBF) at skin basal temperature (SBFBT), together with mean arterial pressure (MAP), heart rate (HR), hemoglobin (Hb), central venous pressure (CVP), lactate, and central or mixed venous oxygen saturation before and 1 h after RBCT. SBF responders were those with a 20% increase in SBFBT after RBCT.

Results

Overall, SBFBT did not significantly change after RBCT [from 79.8 (4.3-479.4) to 83.4 (4.9-561.6); p = 0.67]. A relative increase equal to or more than 20% in SBFBT after RBCT (SBF responders) was observed in 77/175 of RBCT (44%). SBF responders had significantly lower SBFBT [41.3 (4.3-279.3) vs. 136.3 (6.5-479.4) perfusion units; p < 0.01], mixed or central venous oxygen saturation (62.5 ± 9.2 vs. 67.3% ± 12.0%; p < 0.01) and CVP (8.3 ± 5.1 vs. 10.3 ± 5.6 mmHg; p = 0.03) at baseline than non-responders. SBFBT increased in responders [from 41.3 (4.3-279.3) to 93.1 (9.8-561.6) perfusion units; p < 0.01], and decreased in the non-responders [from 136.3 (6.5-479.4) to 80.0 (4.9-540.8) perfusion units; p < 0.01] after RBCT. Pre-transfusion SBFBT was independently associated with a 20% increase in SBFBT after RBCT. Baseline SBFBT had an area under receiver operator characteristic of 0.73 (95% CI, 0.68-0.83) to predict SBFBT increase; A SBFBT of 73.0 perfusion units (PU) had a sensitivity of 71.4% and a specificity of 70.4% to predict SBFBT increase after RBCT. No significant differences in SBFBT were observed after RBCT in different subgroup analyses.

Conclusion

The skin blood flow is globally unaltered by red blood cell transfusions in non-bleeding critically ill patients after initial resuscitation. However, a lower SBFBT at baseline was associated with a relative increase in skin tissue perfusion after RBCT.

How long to wait after local infiltration anaesthesia: systematic review

BACKGROUND

Conflicting evidence exists regarding the optimal waiting time for stable analgesic and vasoconstrictive effects after local infiltration of lidocaine with epinephrine. An objective review is needed to dispel surgical dogma.

METHODS

This systematic review (PROSPERO ID: CRD42022362414) included RCTs and prospective cohort studies. Primary outcomes were (1) onset of analgesia and (2) onset of stable hypoperfusion, assessed directly, or measured indirectly using perfusion imaging. Other data extracted include waiting strategies, means of outcome assessment, anaesthetic concentrations, volume/endpoint of infiltration, and injection sites. Methodological quality was evaluated using the Cochrane risk-of-bias tool for randomized trials. Articles describing waiting strategies were critically appraised by the Joanna Briggs Institute tools.

RESULTS

Twenty-four articles were analysed, comprising 1013 participants. Ten investigated analgesia onset. Their pooled mean was 2.1 min (range 0.4-9.0 min). This varied with anatomic site and targeted nerve diameter. Fourteen articles investigated onset of stable hypoperfusion. Four observed bleeding intraoperatively, finding the minimum time to hypoperfusion at 7.0 min in the eyelid skin and 25.0 min in the upper limb. The ten remaining studies used perfusion imaging, reporting a wide range of results (0.0-30.0 min) due to differences in anatomic sites and depth, resolution and artefacts. Studies using near-infrared reflectance spectroscopy and hyperspectral imaging correlated with clinical observations. Thirteen articles discussed waiting strategies, seven relating to large-volume tumescent local infiltration anaesthesia. Different waiting strategies exist for emergency, arthroscopic and cosmetic surgeries, according to the degree of hypoperfusion required. In tumescent liposuction, waiting 10.0-60.0 min is the norm.

CONCLUSION

Current literature suggests that around 2 min are required for most patients to achieve complete analgesia in all sites and with all anaesthesia concentrations. Waiting around 7 min in eyelids and at least 25 min in other regions results in optimal hypoperfusion. The strategies discussed inform decisions of when and how long to wait.

Use of Bisphosphonates and the Risk of Skin Ulcer: A National Cohort Study Using Data from the French Health Care Claims Database

INTRODUCTION

Previous pre-clinical and pharmacovigilance disproportionality analyses highlighted a safety signal of cutaneous ulcer with bisphosphonate use. Therefore, our objective is to evaluate this risk and assess whether unmeasured confounding factors could explain this association.

METHODS

This study is a population-based cohort study from a representative sample (1/97th) of the French health insurance claims database: Echantillon Généraliste des Bénéficiaires (EGB) from 2006 to 2019. To limit the impact of our study design and methodological choices on any association between skin ulceration and exposure to bisphosphonates, we used several methods: a Cox proportional hazards analysis and a prior event rate ratio (PERR) analysis, using two propensity matched control groups, and either the first episode of incident ulceration or multiple event-time outcomes.

RESULTS

There were 7402 individuals newly exposed to bisphosphonates matched to 29,605 unexposed individuals on propensity score. The primary outcome was skin ulcer occurrence assessed by at least 2 deliveries of wound dressing during the period of one month. Among 6911 individuals newly exposed to bisphosphonates and 28,072 unexposed individuals with no previous skin ulcer, the Cox regression yielded a hazard ratio (HR) of 1.40 (95% CI 1.26-1.56) for newly exposed individuals. Among 7402 exposed and 29,605 unexposed individuals, the PERR analysis found a non-significant HR of 1.03 (95% CI 0.87-1.24). Results were similar on the different sensitivity analyses.

CONCLUSION

No association between bisphosphonate and skin ulcers was found in the French population. The association observed in previous pharmacovigilance studies and in the Cox regression analysis is likely due to unmeasured confounding factors.

Mechanisms of Cardiovascular Changes of Phototherapy in Newborns with Hyperbilirubinemia

During phototherapy of jaundiced newborns, vasodilation occurs in the skin circulation compensated by vasoconstriction in the renal and mesenteric circulation. Furthermore, there is a slight decrease in cardiac systolic volume, and blood pressure, as well as an increase in heart rate and discrete changes in the heart rate variability (HRV). The primary change during phototherapy is the skin vasodilation mediated by multiple mechanisms: 1) Passive vasodilation induced by direct skin heating effect of the body surface and subcutaneous blood vessels, modified by myogenic autoregulation. 2) Active vasodilation mediated via the mechanism provided by axon reflexes through nerve C-fibers and humoral mechanism via nitric oxide (NO) and endothelin 1 (ET-1). During and after phototherapy is a rise in the NO:ET-1 ratio. 3) Regulation of the skin circulation through the sympathetic nerves is unique, but their role in skin vasodilation during phototherapy was not studied. 4) Special mechanism is a photorelaxation independent of the skin heating. Melanopsin (opsin 4) - is thought to play a major role in systemic vascular photorelaxation. Signalling cascade of the photorelaxation is specific, independent of endothelium and NO. The increased skin blood flow during phototherapy is enabled by the restriction of blood flow in the renal and mesenteric circulation. An increase in heart rate indicates activation of the sympathetic system as is seen in the measures of the HRV. High-pressure, as well as low-pressure baroreflexes, may play important role in these adaptation responses. The integrated complex and specific mechanism responsible for the hemodynamic changes during phototherapy confirm adequate and functioning regulation of the neonatal cardiovascular system, including baroreflexes.

Joint Response to Exercise Is Affected by Knee Osteoarthritis: An Infrared Thermography Analysis

Infrared thermography can be used to evaluate the inflammation characterizing the joint environment of OA knees, but there is limited evidence on the response to physical exercise. Identifying the response to exercise of OA knees and the influencing variables could provide important information to better profile patients with different knee OA patterns. Sixty consecutive patients (38 men/22 women, 61.4 ± 9.2 years) with symptomatic knee OA were enrolled. Patients were evaluated with a standardized protocol using a thermographic camera (FLIR-T1020) positioned at 1 m with image acquisition of an anterior view at baseline, immediately after, and at 5 min after a 2-min knee flexion-extension exercise with a 2 kg anklet. Patients' demographic and clinical characteristics were documented and correlated with the thermographic changes. This study demonstrated that the temperature response to exercise in symptomatic knee OA was affected by some demographic and clinical characteristics of the assessed patients. Patients with a poor clinical knee status presented with a lower response to exercise, and women showed a greater temperature decrease than men. Not all evaluated ROIs showed the same trend, which underlines the need to specifically study the different joint subareas to identify the inflammatory component and joint response while investigating knee OA patterns.

The acute adaptation of skin microcirculatory perfusion in vivo does not involve a local response but rather a centrally mediated adaptive reflex

Introduction: Cardiovascular homeostasis involves the interaction of multiple players to ensure a permanent adaptation to each organ's needs. Our previous research suggested that changes in skin microcirculation-even if slight and distal-always evoke an immediate global rather than "local" response affecting hemodynamic homeostasis. These observations question our understanding of known reflexes used to explore vascular physiology, such as reactive hyperemia and the venoarteriolar reflex (VAR). Thus, our study was designed to further explore these responses in older healthy adults of both sexes and to potentially provide objective evidence of a centrally mediated mechanism governing each of these adaptive processes. Methods: Participants (n = 22, 52.5 ± 6.2 years old) of both sexes were previously selected. Perfusion was recorded in both feet by laser Doppler flowmetry (LDF) and photoplethysmography (PPG). Two different maneuvers with opposite impacts on perfusion were applied as challengers to single limb reactive hyperemia evoked by massage and a single leg pending to generate a VAR. Measurements were taken at baseline (Phase I), during challenge (Phase II), and recovery (Phase III). A 95% confidence level was adopted. As proof of concept, six additional young healthy women were selected to provide video imaging by using optoacoustic tomography (OAT) of suprasystolic post-occlusive reactive hyperemia (PORH) in the upper limb. Results: Modified perfusion was detected by LDF and PPG in both limbs with both hyperemia and VAR, with clear systemic hemodynamic changes in all participants. Comparison with data obtained under the same conditions in a younger cohort, previously published by our group, revealed that results were not statistically different between the groups. Discussion: The OAT documentary and analysis showed that the suprasystolic pressure in the arm changed vasomotion in the forearm, displacing blood from the superficial to the deeper plexus vessels. Deflation allowed the blood to return and to be distributed in both plexuses. These responses were present in all individuals independent of their age. They appeared to be determined by the need to re-establish hemodynamics acutely modified by the challenger, which means that they were centrally mediated. Therefore, a new mechanistic interpretation of these exploratory maneuvers is required to better characterize in vivo cardiovascular physiology in humans.

Skin microvascular reactivity in patients with diabetic retinopathy

AIMS

Early detection of microangiopathic complications of diabetes mellitus (DM) is necessary to analyze the patient's condition and prevent disease progression. The study was aimed to investigate the relationship between the presence of retinopathy and decreased reactivity of the microcirculatory bed in patients with diabetes.

METHODS

The study involved 130 subjects: healthy volunteers (n = 48), DM patients without retinopathy (n = 53) and with retinopathy (n = 29). Skin microvascular reactivity was assessed on the forearm using laser Doppler flowmetry with a local heating test combined with occlusion.

RESULTS

The slope of local thermal hyperemia curve (Slope-120) and other parameters of microvascular reactivity showed difference in pairwise comparisons between the groups. Slope-120 had the highest sensitivity (0.759) and specificity (0.717) in detection of diabetic retinopathy. The decrease of Slope-120 was associated with retinopathy (odds ratio (OR) - 8.3 (2.9-24.1), p < 0.001), even after adjusting for other factors (OR - 11.0 (1.6-77.2), p = 0.016).

CONCLUSIONS

Thus, assessment of skin microvascular reactivity may be a useful test for detecting signs of microangiopathic complications and for screening patients in risk group. Decreased microvascular reactivity has been shown to be prospective as an independent indicator of retinopathy in type 1 DM.

Speed-resolved perfusion imaging using multi-exposure laser speckle contrast imaging and machine learning

SIGNIFICANCE

Laser speckle contrast imaging (LSCI) gives a relative measure of microcirculatory perfusion. However, due to the limited information in single-exposure LSCI, models are inaccurate for skin tissue due to complex effects from e.g. static and dynamic scatterers, multiple Doppler shifts, and the speed-distribution of blood. It has been demonstrated how to account for these effects in laser Doppler flowmetry (LDF) using inverse Monte Carlo (MC) algorithms. This allows for a speed-resolved perfusion measure in absolute units %RBC × mm/s, improving the physiological interpretation of the data. Until now, this has been limited to a single-point LDF technique but recent advances in multi-exposure LSCI (MELSCI) enable the analysis in an imaging modality.

AIM

To present a method for speed-resolved perfusion imaging in absolute units %RBC × mm/s, computed from multi-exposure speckle contrast images.

APPROACH

An artificial neural network (ANN) was trained on a large simulated dataset of multi-exposure contrast values and corresponding speed-resolved perfusion. The dataset was generated using MC simulations of photon transport in randomized skin models covering a wide range of physiologically relevant geometrical and optical tissue properties. The ANN was evaluated on in vivo data sets captured during an occlusion provocation.

RESULTS

Speed-resolved perfusion was estimated in the three speed intervals 0 to 1    mm / s , 1 to 10    mm / s , and > 10    mm / s , with relative errors 9.8%, 12%, and 19%, respectively. The perfusion had a linear response to changes in both blood tissue fraction and blood flow speed and was less affected by tissue properties compared with single-exposure LSCI. The image quality was subjectively higher compared with LSCI, revealing previously unseen macro- and microvascular structures.

CONCLUSIONS

The ANN, trained on modeled data, calculates speed-resolved perfusion in absolute units from multi-exposure speckle contrast. This method facilitates the physiological interpretation of measurements using MELSCI and may increase the clinical impact of the technique.

Wavelet analysis of laser Doppler microcirculatory signals: Current applications and limitations

Laser Doppler flowmetry (LDF) has long been considered a gold standard for non-invasive assessment of skin microvascular function. Due to the laser Doppler (LD) microcirculatory signal's complex biological and physiological context, using spectral analysis is advisable to extract as many of the signal's properties as feasible. Spectral analysis can be performed using either a classical Fourier transform (FT) technique, which has the disadvantage of not being able to localize a signal in time, or wavelet analysis (WA), which provides both the time and frequency localization of the inspected signal. So far, WA of LD microcirculatory signals has revealed five characteristic frequency intervals, ranging from 0.005 to 2 Hz, each of which being related to a specific physiological influence modulating skin microcirculatory response, providing for a more thorough analysis of the signals measured in healthy and diseased individuals. Even though WA is a valuable tool for analyzing and evaluating LDF-measured microcirculatory signals, limitations remain, resulting in a lack of analytical standardization. As a more accurate assessment of human skin microcirculation may better enhance the prognosis of diseases marked by microvascular dysfunction, searching for improvements to the WA method is crucial from the clinical point of view. Accordingly, we have summarized and discussed WA application and its limitations when evaluating LD microcirculatory signals, and presented insight into possible future improvements. We adopted a novel strategy when presenting the findings of recent studies using WA by focusing on frequency intervals to contrast the findings of the various studies undertaken thus far and highlight their disparities.

Structural and functional state of various parts of skin microcirculation at an early stage of hypertension in working-age men

STUDY PURPOSE

To conduct a cross-sectional study on the structural and functional characteristics of various parts of skin microcirculation in working-age men with newly diagnosed hypertension (HTN).

MATERIALS AND METHODS

The study included 118 male participants (ages 30 to 60) who were not regularly taking any medicine, had no medical complaints, and subjectively considered themselves healthy at the time of study. All participants underwent a cross-sectional comprehensive medical examination. The following tests were performed: complete blood count, biochemical blood tests, video capillaroscopy (VCS), laser Doppler flowmetry (LDF) and photoplethysmography (PPG) on the left hand fingers, determination of flow-mediated vasodilation of the brachial artery, echocardiography, ultrasound of extracranial and femoral arteries, 24-h ambulatory blood pressure monitoring (ABPM). According to ABPM data, the participants were divided into two equal groups called a control group(CG) and a hypertension group(HG). There were 59 participants with normal BP in CG, and 59 participants with newly diagnosed HTN in HG.

RESULTS

Nailfold VCS of the ring finger revealed no significant differences between the groups at the level of exchange microvessels. According to LDF data, there was no decrease in tissue perfusion and signs of an increase in the activity of endothelial, neurogenic, and myogenic regulation of the tone of precapillary arterioles in the HTN group. According to PPG of the index finger, in contrast to CG, HTN participants had significantly higher values of the following parameters: normalized augmentation index (Alp75) - 3.8 % and - 5.25 % (p < 0.005), stiffness index (SI) - 7.6 m/s and 7.35 m/s (p < 0.05), reflection index (RI) - 36.5 % and 28.4 % (p < 0.005), respectively.

DISCUSSION

Working-age men in the early stage of HTN have neither capillary rarefaction nor an increase in the tone of skin precapillary arterioles. The largest contribution to peripheral vascular resistance in the onset of HTN is most likely made by large muscular arterioles, in which the neurogenic regulation of vascular tone predominates.

Efficacy of Radiofrequency Thermocoagulation of the Thoracic Sympathetic Nerve versus Chemical Excision in Pain Caused by Raynaud's Disease

Objective

To investigate the effectiveness and safety of computed tomography (CT)-guided radiofrequency thermocoagulation (RFTC) of the thoracic sympathetic nerve versus chemical resection (CTS) for the treatment of pain caused by Raynaud's disease.

Methods

Patients who underwent CTS or thoracic sympathetic nerve RFTC between March 2012 and March 2021 were enrolled in this retrospective study. There were 28 cases in the alcohol group (Group A) and 44 in the radiofrequency group (Group R). Visual analog scores (VAS) were collected from patients at different time points, as well as preoperative and postoperative finger end perfusion index (PI) and hand temperature (T). The efficiency, postoperative recurrence rate, complications, and improvement in postoperative quality of life were observed in both groups.

Results

Pain scores at different follow-up times after surgery decreased in both groups compared to the preoperative period (P < 0.05). Postoperative T and PI were higher in both groups than preoperatively all (P < 0.05). The recurrence rate was higher in the R group than in the A group. Postoperative complications were observed in 13.6% and 25% of patients in groups R and A, respectively. Meanwhile, the postoperative quality of life improved in both groups, but the radiofrequency (RF) group was better than the alcohol group in terms of improvement in quality of life (P < 0.05).

Conclusion

Both CT-guided CTS and RFTC of the thoracic sympathetic nerve provided good treatment outcomes. However, the RF group was superior to the alcohol group in terms of complication rate and quality of life improvement.

Vascular endothelium as a target tissue for short-term exposure to low-frequency noise that increases cutaneous blood flow

Harmful health effects of exposure to low-frequency noise (LFN) defined as noise with frequencies at ≤100 Hz on the circulatory system have been a concern. However, there has been no study on the effects of exposure to LFN on the circulatory system with consideration of its frequencies and decibels. In this study, the effects of short-term exposure to broad-band LFNs and their pure-tone components (pure-tone LFNs) on cutaneous blood flow in the extremities including the hands were investigated. In our fieldwork study, we first sampled some kinds of common broad-band LFNs. Our human study then showed that broad-band LFN with a narrower frequency range more strongly increased cutaneous blood flow than did broad-band LFN with a wider frequency range. Pure-tone LFNs of 70-100 Hz at ≤85 dB(Z), but not pure-tone LFNs exceeding 100 Hz, further increased levels of cutaneous blood flow. Our wavelet-transform spectrum analysis of cutaneous blood flow next revealed that the nitric oxide (NO)-dependent and -independent vascular activities of the vascular endothelium were specifically increased by exposure to pure-tone LFN. Our animal study again indicated that exposure to pure-tone LFN increased cutaneous blood flow in mice with impairments of bilateral inner ears as well as cutaneous blood flow in control mice, suggesting a limited effect of inner ear function on the LFN-mediated increase in cutaneous blood flow. The NO-dependent suppressive effect of pure-tone LFN on cutaneous blood flow was confirmed by inhibition of vascular endothelial activity through intravenous injection of an NO inhibitor in wild-type mice. Taken together, the results of this study demonstrated that the vascular endothelium is a target tissue of LFN and that NO is an effector of the LFN-mediated increase in cutaneous blood flow. Since improvement of peripheral circulation could generally promote human health, short-term exposure to LFN may be beneficial for health.

Aberrant amino acid metabolism promotes neurovascular reactivity in rosacea

Rosacea is a chronic skin disorder characterized by abnormal neurovascular and inflammatory conditions on the central face. Despite increasing evidence suggesting that rosacea is associated with metabolic disorders, the role of metabolism in rosacea pathogenesis remains unknown. Here, via a targeted metabolomics approach, we characterized significantly altered metabolic signatures in patients with rosacea, especially for amino acid-related metabolic pathways. Among these, glutamic acid and aspartic acid were highlighted and positively correlated with the disease severity in patients with rosacea. We further demonstrated that glutamic acid and aspartic acid can facilitate the development of erythema and telangiectasia, typical features of rosacea, in the skin of mice. Mechanistically, glutamic acid and aspartic acid stimulated the production of vasodilation-related neuropeptides from peripheral neurons and keratinocytes and induced the release of nitric oxide from endothelial cells and keratinocytes. Interestingly, we provided evidence showing that doxycycline can improve the symptoms of patients with rosacea possibly by targeting the amino acid metabolic pathway. These findings reveal that abnormal amino acid metabolism promotes neurovascular reactivity in rosacea and raise the possibility of targeting dysregulated metabolism as a promising strategy for clinical treatment.

Skin Microhemodynamics and Mechanisms of Its Regulation in Type 2 Diabetes Mellitus

The review presents modern ideas about peripheral microhemodynamics, approaches to the ana-lysis of skin blood flow oscillations and their diagnostic significance. Disorders of skin microhemodynamics in type 2 diabetes mellitus (DM) and the possibility of their interpretation from the standpoint of external and internal interactions between systems of skin blood flow regulation, based on a comparison of couplings in normal and pathological conditions, including models of pathologies on animals, are considered. The factors and mechanisms of vasomotor regulation, among them receptors and signaling events in endothelial and smooth muscle cells considered as models of microvessels are discussed. Attention was drawn to the disturbance of Ca2+-dependent regulation of coupling between vascular cells and NO-dependent regulation of vasodilation in diabetes mellitus. The main mechanisms of insulin resistance in type 2 DM are considered to be a defect in the number of insulin receptors and impaired signal transduction from the receptor to phosphatidylinositol-3-kinase and downstream targets. Reactive oxygen species plays an important role in vascular dysfunction in hyperglycemia. It is assumed that the considered molecular and cellular mechanisms of microhemodynamics regulation are involved in the formation of skin blood flow oscillations. Parameters of skin blood microcirculation can be used as diagnostic and prognostic markers for assessing the state of the body.

Optoacoustic Imaging Offers New Insights into In Vivo Human Skin Vascular Physiology

Functional imaging with new photoacoustic tomography (PAT) offers improved spatial and temporal resolution quality in in vivo human skin vascular assessments. In the present study, we followed a suprasystolic reactive hyperemia (RH) maneuver with a multi-spectral optoacoustic tomography (MSOT) system. A convenience sample of ten participants, both sexes, mean age of 35.8 ± 13.3 years old, was selected. All procedures were in accordance with the principles of good clinical practice and approved by the institutional ethics committee. Images were obtained at baseline (resting), during occlusion, and immediately after pressure release. Observations of the RH by PAT identified superficial and deeper vascular structures parallel to the skin surface as part of the human skin vascular plexus. Furthermore, PAT revealed that the suprasystolic occlusion impacts both plexus differently, practically obliterating the superficial smaller vessels and evoking stasis at the deeper, larger structures in real-time (live) conditions. This dual effect of RH on the skin plexus has not been explored and is not considered in clinical settings. Thus, RH seems to represent much more than the local microvascular reperfusion as typically described, and PAT offers a vast potential for vascular clinical and preclinical research.

Quantitative Characterization of Age-Related Changes in Peripheral Vessels of a Human Palm Using Raster-Scan Optoacoustic Angiography

The analysis of age-related changes in skin vessels based on optoacoustic angiographic images during the in vivo skin monitoring of healthy volunteers at different ages is reported. As a result of a quantitative analysis of the three-dimensional OA images, the age-associated differences in the following image parameters were revealed: image intensity, ratio of blood content at different characteristics depths, total vessel length, and number of branches. The reported approach can be effectively employed for automatic assessment and monitoring of age-related vascular changes in the skin and underlying tissues.

In vivo dose-response analysis to acetylcholine: pharmacodynamic assessment by polarized reflectance spectroscopy

Transdermal iontophoresis offers an in vivo alternative to the strain-gauge model for measurement of vascular function but is limited due to lack of technical solutions for outcome assessment. The aims of this study were to, after measurement by polarized reflectance spectroscopy (PRS), use pharmacodynamic dose–response analysis on responses to different concentrations of acetylcholine (ACh); and to examine the effect of three consecutively administered iontophoretic current pulses. The vascular responses in 15 healthy volunteers to iontophorised ACh (5 concentrations, range 0.0001% to 1%, three consecutive pulses of 0.02 mA for 10 min each) were recorded using PRS. Data were fitted to a four-parameter logistic dose response model and compared. Vascular responses were quantifiable by PRS. Similar pharmacodynamic dose response curves could be generated irrespectively of the ACh concentration. Linearly increasing maximum vasodilatory responses were registered with increasing concentration of ACh. A limited linear dose effect of the concentration of ACh was seen between pulses. Polarized reflectance spectroscopy is well suited for measuring vascular responses to iontophoretically administrated ACh. The results of this study support further development of iontophoresis as a method to study vascular function and pharmacological responses in vivo.

Skin microvascular function, as assessed with laser speckle contrast imaging, is impaired in untreated essential and masked hypertension

Skin microcirculation has been proposed as a model of generalized microvascular function. Laser speckle contrast imaging (LSCI) is a novel, noninvasive method to assess skin microvascular function (SMF). To date, SMF data in hypertension are conflicting, and no study with LSCI exists. In addition, the application of LSCI in masked hypertension is scarce. We assessed SMF with LSCI coupled with postocclusive reactive hyperemia (PORH) in patients with newly diagnosed untreated essential hypertension (UHT) and masked hypertension (MH) compared to healthy normotensive (NT) individuals. We enrolled consecutive UHT and MH patients and NT individuals matched for age, sex, body mass index, and smoking status. All participants underwent SMF assessment by LSCI coupled with PORH (PeriCam PSI system, Perimed, Sweden). Correlation analyses were performed between SMF and common cardiovascular risk factors and BP parameters. In total, 70 UHT patients, 20 MH patients and 40 NT individuals were enrolled. UHT and MH patients exhibited significantly impaired SMF compared to NT individuals (UHT patients: base-to-peak flux (p < 0.001)), PORH amplitude (p < 0.001); MH patients: base-to-peak flux (p = 0.013), PORH amplitude (p = 0.022). MH patients did not differ compared to UHT patients. SMF was negatively associated with office, ambulatory and central BP. SMF was negatively associated with blood lipids and smoking. Hypertensive status was the single most important predictor of SMF. UHT and MH patients exhibit impaired SMF compared to NT individuals. MH patients did not differ compared to UHT patients. SMF is negatively associated with BP and cardiovascular risk factors. LSCI could be implemented as a useful tool to investigate SMF in hypertension.

Vascular ageing and peripheral pulse: an improved model for assessing their relationship

Objective.Vascular ageing is associated with several alterations, including arterial stiffness and endothelial dysfunction. Such alterations represent an independent factor in the development of cardiovascular disease (CVD). In our previous works we demonstrated the alterations occurring in the vascular system are themselves reflected in the shape of the peripheral waveform; thus, a model that describes the waveform as a sum of Gaussian curves provides a set of parameters that successfully discriminate betweenunder(≤35 years old) andoversubjects (>35 years old). In the present work, we explored the feasibility of a new decomposition model, based on a sum of exponential pulses, applied to the same problem.Approach.The first processing step extracts each pulsation from the input signal and removes the long-term trend using a cubic spline with nodes between consecutive pulsations. After that, a Least Squares fitting algorithm determines the set of optimal model parameters that best approximates each single pulse. The vector of model parameters gives a compact representation of the pulse waveform that constitutes the basis for the classification step. Each subject is associated to his/her 'representative' pulse waveform, obtained by averaging the vector parameters corresponding to all pulses. Finally, a Bayesan classifier has been designed to discriminate the waveforms of under and over subjects, using the leave-one-subject-out validation method.Main results.Results indicate that the fitting procedure reaches a rate of 96% in under subjects and 95% in over subjects and that the Bayesan classifier is able to correctly classify 91% of the subjects with a specificity of 94% and a sensibility of 84%.Significance.This study shows a sensible vascular age estimation accuracy with a multi-exponential model, which may help to predict CVD.

Lower Limb Perfusion Asymmetries in Humans at Rest and Following Activity—A Collective View

The significance of lower limb perfusion asymmetries remains unknown in healthy individuals. Our study aims to understand how factors such as posture, sex, age, and body weight relate to perfusion. Data from studies previously published by our group, including experiments using laser Doppler flowmetry as the gold standard for perfusion measurements in baseline, (various) challenge, and recovery phases was assembled from a total of 139 healthy participants. Body position was shown to be a primary determinant of perfusion asymmetry, especially in women. Effects of sex and age were also analyzed. In a supine position, perfusion asymmetries seemed to relate negatively in the aged group of participants, where challenge and recovery seemed to follow different processes. In the upright position, young men and women have shown comparable distributions and asymmetry ratios at baseline and recovery. In the aged group, differences between sexes were observed at baseline, but again, the course of the asymmetry ratios with challenge was essentially similar in men and women. Our analysis suggests that ageing is a critical determinant in our upright study sample, as higher baseline asymmetries and longer recoveries after challenge were linked in older males with higher body mass index (BMI).

Post-ischemic skin peak oxygen saturation is associated with cardiovascular risk factors: a Swedish cohort study

The objective of this study was to explore the associations between skin microcirculatory function and established cardiovascular risk factors in a large Swedish cohort. As part of the Swedish CArdioPulmonary bioImage Study (SCAPIS), microcirculatory data were acquired at Linköping University hospital, Linköping, Sweden during 2016-2017. The subjects, aged 50-64 years, were randomly selected from the national population register. Microcirculatory reactivity was assessed using a 5-min arterial occlusion-release protocol. Comprehensive skin microcirculatory data were continuously acquired by using a fiberoptic probe placed on the lower right arm. After exclusion of missing data (208), 1557 subjects were remaining. Among the parameters, skin microcirculatory peak oxygen saturation after occlusion release, had the strongest relationship to the cardiovascular risk factors. The linear associations between peak oxygen saturation and cardiovascular risk factors were analyzed adjusted for age and sex. We found a negative association with peak oxygen saturation (standardized regression coefficient) for blood pressure (systolic -0.05 (95% CI: -0.10;-0.003) and diastolic -0.05 (-0.10; -0.003)), BMI -0.18 (-0.23; -0.13), waist circumference (males -0.20 (-0.32; -0.16), females -0.18 (-0.25; -0.11)), prevalent diabetes -0.31 (-0.49; -0.12), hypertension -0.30 (-0.42; -0.18), dyslipidemia -0.24 (-0.40; -0.09), fasting glucose level -0.06 (-0.12; -0.01), HbA1c -0.07 (-0.12; -0.02), triglyceride level -0.09 (-0.14; -0.04), hsCRP -0.12 (-0.17; -0.07), and current smoker versus never smoked -0.50 (-0.67; -0.34). A positive association with peak oxygen saturation was found for cholesterol level 0.05 (0.005; 0.11) and HDL 0.11 (0.06; 0.17). This is the first study showing that post-ischemic skin microvascular peak oxygen saturation is associated with virtually all established cardiovascular risk factors in a population-based middle-aged cohort.

Vasomotion analysis of speed resolved perfusion, oxygen saturation, red blood cell tissue fraction, and vessel diameter: Novel microvascular perspectives

BACKGROUND

Vasomotion is the spontaneous oscillation in vascular tone in the microcirculation and is believed to be a physiological mechanism facilitating the transport of blood gases and nutrients to and from tissues. So far, Laser Doppler flowmetry has constituted the gold standard for in vivo vasomotion analysis.

MATERIALS AND METHODS

We applied vasomotion analysis to speed-resolved perfusion, oxygen saturation, red blood cell tissue (RBC) tissue fraction, and average vessel diameter from five healthy individuals at rest measured by the newly developed Periflux 6000 EPOS system over 10 minutes. Magnitude scalogram and the time-averaged wavelet spectra were divided into frequency intervals reflecting endothelial, neurogenic, myogenic, respiratory, and cardiac function.

RESULTS

Recurrent high-intensity periods of the myogenic, neurogenic, and endothelial frequency intervals were found. The neurogenic activity was considerably more pronounced for the oxygen saturation, RBC tissue fraction, and vessel diameter signals, than for the perfusion signals. In a correlation analysis we found that changes in perfusion in the myogenic, neurogenic, and endothelial frequency intervals precede changes in the other signals. Furthermore, changes in average vessel diameter were in general negatively correlated to the other signals in the same frequency intervals, indicating the importance of capillary recruitment.

CONCLUSION

We conclude that vasomotion can be observed in signals reflecting speed resolved perfusion, oxygen saturation, RBC tissue fraction, and vessel diameter. The new parameters enable new aspects of the microcirculation to be observed.

Detection of microvascular changes in systemic sclerosis and other rheumatic diseases

Morphological and functional analysis of the microcirculation are objective outcome measures that are recommended for use in the presence of clinical signs of altered peripheral blood flow (such as Raynaud phenomenon), which can occur in systemic sclerosis (SSc) and other autoimmune rheumatic diseases. Several advanced non-invasive tools are available for monitoring the microcirculation, including nailfold videocapillaroscopy, which is the best-studied and most commonly used method for distinguishing and quantifying microvascular morphological alterations in SSc. Nailfold videocapillaroscopy can also be used alongside laser Doppler techniques to assist in the early diagnosis and follow-up of patients with dermatomyositis or mixed connective tissue disease. Power Doppler ultrasonography, which has been used for many years to evaluate the vascularity of synovial tissue in rheumatoid arthritis, is another promising tool for the analysis of skin and nailbed capillary perfusion in other autoimmune rheumatic diseases. Other emerging methods include raster-scanning optoacoustic mesoscopy, which offers non-invasive high-resolution 3D visualization of capillaries and has been tested in psoriatic arthritis and SSc. The principle functions and operative characteristics of several non-invasive tools for analysing microvascular changes are outlined in this Review, and the clinical roles of validated or tested imaging methods are discussed for autoimmune rheumatic diseases.

Spectral analysis of blood flow oscillations to assess the plantar skin blood flow regulation in response to preconditioning local vibrations

BACKGROUND

Local vibration has shown promise in improving skin blood flow and wound healing. However, the underlying mechanism of local vibration as a preconditioning intervention to alter plantar skin blood flow after walking is unclear.

OBJECTIVE

The objective was to use wavelet analysis of skin blood flow oscillations to investigate the effect of preconditioning local vibration on plantar tissues after walking.

METHODS

A double-blind, repeated measures design was tested in 10 healthy participants. The protocol included 10-min baseline, 10-min local vibrations (100 Hz or sham), 10-min walking, and 10-min recovery periods. Skin blood flow was measured over the first metatarsal head of the right foot during the baseline and recovery periods. Wavelet amplitudes after walking were expressed as the ratio of the wavelet amplitude before walking.

RESULTS

The results showed the significant difference in the metabolic (vibration 10.06 ± 1.97, sham 5.78 ± 1.53, p < 0.01) and neurogenic (vibration 7.45 ± 1.54, sham 4.78 ± 1.22, p < 0.01) controls. There were no significant differences in the myogenic, respiratory and cardiac controls between the preconditioning local vibration and sham conditions.

CONCLUSIONS

Our results showed that preconditioning local vibration altered the normalization rates of plantar skin blood flow after walking by stimulating the metabolic and neurogenic controls.

Assessment of microvascular function and pharmacological regulation in genetically confirmed familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is a genetic lipid disorder leading to accelerated atherosclerosis, premature cardiovascular disease and death. Microvascular endothelial dysfunction is one of the earliest vascular pathology manifestations and may precede symptomatic atherosclerosis.

METHODS

In this paper, microvascular endothelial function was assessed in FH patients and healthy controls using flow mediated skin fluorescence (FMSF), based on measurements of nicotinamide adenine dinucleotide fluorescence intensity during brachial artery occlusion (ischemic response, IR) and immediately after occlusion (hyperemic response, HR). Low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) were used to assess its relation with microvascular parameters evaluated in vivo.

RESULTS

LDL-C levels were significantly correlated to both HR_max (r = -0.548, p = 0.001) and HR_index (r = -0.514, p = 0.003). Similarly, there was a significant inverse correlation of TC levels and both HR_max (r = -0.538, p = 0.002) and HR_index (r = -0.512, p = 0.003). All FMSF parameters were found lower in FH patients compared to age- and sex-matched healthy controls. Hyperemic response (HR_max) was significantly higher in FH patients examined on statins compared to those without any lipid-lowering treatment (19.9 ± 3.1 vs. 16.4 ± 4.2 respectively, p = 0.022).

CONCLUSIONS

This study shows that, in patients with FH, microvascular endothelial-dependent hyperemic response is impaired and inversely correlated to plasma cholesterol levels. Microvascular function was found better in FH patients receiving statins.

Type 2 diabetes impairs vascular responsiveness to nitric oxide, but not the venoarteriolar reflex or post-occlusive reactive hyperaemia in forearm skin

The venoarteriolar reflex (VAR) is a local mechanism by which vasoconstriction is mediated in response to venous congestion. This response may minimize tissue overperfusion, preventing capillary damage and oedema. Post-occlusive reactive hyperaemia (PORH) is used to assess microvascular function by performing a brief local arterial occlusion resulting in a subsequent rapid transient vasodilation. In the current study, we hypothesized that type 2 diabetes (T2D) attenuates VAR and PORH responses in forearm skin in vivo. In 11 healthy older adults (Control, 58 ± 8 years) and 13 older adults with controlled T2D (62 ± 10 years), cutaneous blood flow measured by laser-Doppler flowmetry was monitored following a 3-min venous occlusion of 45 mm Hg that elicited the VAR, followed by a 3-min recovery period and then a 5-min arterial occlusion of 240 mm Hg that induced PORH. Finally, sodium nitroprusside, a nitric oxide donor, was administered to induce maximum vasodilation. VAR and PORH variables were similar between groups. By contrast, maximal cutaneous blood flow induced by sodium nitroprusside was lower in the T2D group. Taken together, our observations indicate that T2D impairs vascular smooth muscle responsiveness to nitric oxide, but not VAR and PORH in forearm skin.

Synthetic, Natural, and Semisynthetic Polymer Carriers for Controlled Nitric Oxide Release in Dermal Applications: A Review

Nitric oxide (NO•) is a free radical gas, produced in the human body to regulate physiological processes, such as inflammatory and immune responses. It is required for skin health; therefore, a lack of NO• is known to cause or worsen skin conditions related to three biomedical applications- infection treatment, injury healing, and blood circulation. Therefore, research on its topical release has been increasing for the last two decades. The storage and delivery of nitric oxide in physiological conditions to compensate for its deficiency is achieved through pharmacological compounds called NO-donors. These are further incorporated into scaffolds to enhance therapeutic treatment. A wide range of polymeric scaffolds has been developed and tested for this purpose. Hence, this review aims to give a detailed overview of the natural, synthetic, and semisynthetic polymeric matrices that have been evaluated for antimicrobial, wound healing, and circulatory dermal applications. These matrices have already set a solid foundation in nitric oxide release and their future perspective is headed toward an enhanced controlled release by novel functionalized semisynthetic polymer carriers and co-delivery synergetic platforms. Finally, further clinical tests on patients with the targeted condition will hopefully enable the eventual commercialization of these systems.

Updated Role of Neuropeptide Y in Nicotine-Induced Endothelial Dysfunction and Atherosclerosis

Cardiovascular disease is the leading cause of death worldwide. Endothelial dysfunction of the arterial vasculature plays a pivotal role in cardiovascular pathogenesis. Nicotine-induced endothelial dysfunction substantially contributes to the development of arteriosclerotic cardiovascular disease. Nicotine promotes oxidative inflammation, thrombosis, pathological angiogenesis, and vasoconstriction, and induces insulin resistance. However, the exact mechanism through which nicotine induces endothelial dysfunction remains unclear. Neuropeptide Y (NPY) is widely distributed in the central nervous system and peripheral tissues, and it participates in the pathogenesis of atherosclerosis by regulating vasoconstriction, energy metabolism, local plaque inflammatory response, activation and aggregation of platelets, and stress and anxiety-related emotion. Nicotine can increase the expression of NPY, suggesting that NPY is involved in nicotine-induced endothelial dysfunction. Herein, we present an updated review of the possible mechanisms of nicotine-induced atherosclerosis, with a focus on endothelial cell dysfunction associated with nicotine and NPY.

Drug-induced peripheral oedema: An aetiology-based review

Many drugs are responsible, through different mechanisms, for peripheral oedema. Severity is highly variable, ranging from slight oedema of the lower limbs to anasarca pictures as in the capillary leak syndrome. Although most often noninflammatory and bilateral, some drugs are associated with peripheral oedema that is readily erythematous (eg, pemetrexed) or unilateral (eg, sirolimus). Thus, drug-induced peripheral oedema is underrecognized and misdiagnosed, frequently leading to a prescribing cascade. Four main mechanisms are involved, namely precapillary arteriolar vasodilation (vasodilatory oedema), sodium/water retention (renal oedema), lymphatic insufficiency (lymphedema) and increased capillary permeability (permeability oedema). The underlying mechanism has significant impact on treatment efficacy. The purpose of this review is to provide a comprehensive analysis of the main causative drugs by illustrating each pathophysiological mechanism and their management through an example of a drug.

Independent and combined impact of hypoxia and acute inorganic nitrate ingestion on thermoregulatory responses to the cold

Purpose

This study assessed the impact of normobaric hypoxia and acute nitrate ingestion on shivering thermogenesis, cutaneous vascular control, and thermometrics in response to cold stress.

Method

Eleven male volunteers underwent passive cooling at 10 °C air temperature across four conditions: (1) normoxia with placebo ingestion, (2) hypoxia (0.130 F_iO₂) with placebo ingestion, (3) normoxia with 13 mmol nitrate ingestion, and (4) hypoxia with nitrate ingestion. Physiological metrics were assessed as a rate of change over 45 min to determine heat loss, and at the point of shivering onset to determine the thermogenic thermoeffector threshold.

Result

Independently, hypoxia expedited shivering onset time (p = 0.05) due to a faster cooling rate as opposed to a change in central thermoeffector thresholds. Specifically, compared to normoxia, hypoxia increased skin blood flow (p = 0.02), leading to an increased core-cooling rate (p = 0.04) and delta change in rectal temperature (p = 0.03) over 45 min, yet the same rectal temperature at shivering onset (p = 0.9). Independently, nitrate ingestion delayed shivering onset time (p = 0.01), mediated by a change in central thermoeffector thresholds, independent of changes in peripheral heat exchange. Specifically, compared to placebo ingestion, no difference was observed in skin blood flow (p = 0.5), core-cooling rate (p = 0.5), or delta change in rectal temperature (p = 0.7) over 45 min, while nitrate reduced rectal temperature at shivering onset (p = 0.04). No interaction was observed between hypoxia and nitrate ingestion.

Conclusion

These data improve our understanding of how hypoxia and nitric oxide modulate cold thermoregulation.

[Functional integrity of aging skin, from cutaneous biology to anti-aging strategies]

The skin is a sentinel organ making easily visible the passing of time. Chronological and environmental aging weakens skin structure and functions. The skin barrier, the elastic and mechanical properties of the cutaneous tissue as well as its vascular reactivity are impacted by aging. The barrier dysfunction in aged skin is caused by defects in epidermal keratinocytes renewal and differentiation notably linked to abnormal expression of microRNAs regulating cell death and autophagy. An abnormal balance between synthesis and degradation of matrix proteins modifies the mechanical properties of the dermis in aged skin. Finally, a reduction of the vascular reactivity linked to endothelial dysfunctions is observed in elderly people. These biological processes can be targeted by therapeutic approaches either topical or systemic, especially using anti-oxydants or senolytics. These anti-aging strategies might contribute to restore, at least in part, the functional integrity of aged skin.