Endothelial Glycocalyx in Aging and Age-related Diseases

Age matters: A Secondary Analysis of Endothelial Biomarkers in the Prehospital Tranexamic Acid for Traumatic Brain Injury Trial

BACKGROUND

Injured older adults account for nearly 25% of trauma admissions nationwide with increased morbidity and mortality compared with younger adults. Endothelial dysfunction has been associated with poor outcomes in trauma patients. We hypothesized that posttraumatic endothelial changes in older versus younger adult trauma patients will be different with worse outcomes in older adults.

METHODS

This is a retrospective secondary analysis of the "Tranexamic Acid (TXA) in Traumatic Brain Injury" prehospital database (2015-2017). We studied patients with admission endothelial biomarkers: intercellular adhesion molecule 1, angiotensin 1, thrombomodulin, vascular cell adhesion molecule 1 (VCAM 1), angiotensin 2, syndecan-1, and thrombospondin. We divided patients into age quartiles and compared the oldest quartile (older age [OA] group) with the three youngest quartiles (younger age [YA] group). In-hospital, discharge, and mortality outcomes were compared. Significance was set at p < 0.05.

RESULTS

A total of 436 patients were included. The mean age in OA group was 66 years (55-88 years, n = 108). The YA mean age was 30 years (15-54 years, n = 328). There was no difference between OA and YA in rates of blunt trauma (98.1% vs. 96.3%, p = 0.61), head abbreviated injury scale (mean, 2.83 vs. 2.93; p = 0.582), or Injury Severity Score (mean, 21 vs. 19; p = 0.29). Tranexamic acid dosing was not different between cohorts (p = 0.571). Overall, the OA group had higher thrombomodulin (median, 693.3 vs. 592.9 pg/mL; p = 0.0008), VCAM 1 (median, 70,852 vs. 59,738 pg/mL; p = 0.0015), and angiotensin 2 (median, 165.3 vs. 134.2 pg/mL; p = 0.005). When comparing endothelial biomarkers of OA to each YA age quartile subsets, in the 2g TXA group OA patients had significantly higher syndecan-1 levels from a subset of YA (37 to 54-year-olds, p = 0.034). In the 2g TXA group OA patients had significantly lower plasma thrombomodulin, angiotensin 2, and VCAM 1 (p = 0.00001, p = 0.0032, and p = 0.0002, respectively) than patients in the placebo group. None of the biomarkers were independent predictors of 28-day mortality.

CONCLUSION

Despite similar injury patterns, OA presented with higher admission endothelial plasma biomarkers. The OA patients receiving 2 g of TXA had significantly different endothelial biomarker levels versus YA group. These differences suggest that OA patients have a different baseline endothelial function prior to injury and that TXA may have a more pronounced effect on injured OA versus YA endothelium.

LEVEL OF EVIDENCE

Therapeutic Care Management; Level IV.

Functions and application of circRNAs in vascular aging and aging-related vascular diseases

Circular RNAs (circRNAs), constituting a novel class of endogenous non-coding RNAs generated through the reverse splicing of mRNA precursors, possess the capacity to regulate gene transcription and translation. Recently, the pivotal role of circRNAs in controlling vascular aging, as well as the pathogenesis and progression of aging-related vascular diseases, has garnered substantial attention. Vascular aging plays a crucial role in the increased morbidity and mortality of the elderly. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are crucial components of the intima and media layers of the vascular wall, respectively, and are closely involved in the mechanisms underlying vascular aging and aging-related vascular diseases. The review aims to provide a comprehensive exploration of the connection between circRNAs and vascular aging, as well as aging-related vascular diseases. Besides, circRNAs, as potential diagnostic markers or therapeutic targets for vascular aging and aging-related vascular diseases, will be discussed thoroughly, along with the challenges and limitations of their clinical application. Investigating the role and molecular mechanisms of circRNAs in vascular aging and aging-related vascular diseases will provide a novel insight into early diagnosis and therapy, and even effective prognosis assessment of these conditions.

Sepsis-associated endothelial glycocalyx damage: a review of animal models, clinical evidence, and molecular mechanisms

In the mammalian cardiovascular system, endothelial glycocalyx is a gel-like layer that covers the luminal surface of endothelial cells (ECs) and plays crucial roles in vascular homeostasis, permeability and leukocyte adhesion. Degradation of this structure occurs early in sepsis and becomes accordingly dysfunctional. In severe cases, it is not self-regulated by the organism. However, the relationship between the glycocalyx and the occurrence and development of sepsis remains poorly understood. One possibility is that thinned glycocalyx promotes leukocyte recognition and adhesion, thereby facilitating the elimination of pathogens from infected areas. This may represent a protective mechanism developed by the organism during through evolutionary processes. However, if the damage persists and disrupts the dynamic balance of the microcirculation, interstitial edema or organ failure can occur. Thus, we asked the questions, what is the precise composition and structure of the glycocalyx? How is it degraded? What animal models are available to study the relationship between the glycocalyx and sepsis? What glycocalyx biomarkers are found in the blood of patients with sepsis? To determine whether sepsis can be treated by interfering with the glycocalyx, this study provides a systematic summary and discussion of the latest progress in addressing these questions.

Factors influencing glycocalyx degradation: a narrative review

The glycocalyx is a layer of villus-like structure covering the luminal surface of vascular endothelial cells. Damage to the glycocalyx has been proven linked to the development of many diseases. However, the factors that promote damage to the glycocalyx are not fully elaborated. This review summarizes factors leading to the reduction of the glycocalyx in detail, including inflammatory factors, ischemia-reperfusion, oxidative stress, lipids, glucose, high sodium, female sex hormones and others. Additionally, the mechanisms underlying its degradation are discussed. To better prevent and treat related diseases induced by glycocalyx degradation, it is a meaningful measure to avoid these factors.

From Mechanisms to Medicine: Neurovascular Coupling in the Diagnosis and Treatment of Cerebrovascular Disorders: A Narrative Review

Neurovascular coupling (NVC) refers to the process of local changes in cerebral blood flow (CBF) after neuronal activity, which ensures the timely and adequate supply of oxygen, glucose, and substrates to the active regions of the brain. Recent clinical imaging and experimental technology advancements have deepened our understanding of the cellular mechanisms underlying NVC. Pathological conditions such as stroke, subarachnoid hemorrhage, cerebral small vascular disease, and vascular cognitive impairment can disrupt NVC even before clinical symptoms appear. However, the complexity of the underlying mechanism remains unclear. This review discusses basic and clinical experimental evidence on how neural activity sensitively communicates with the vasculature to cause spatial changes in blood flow in cerebrovascular diseases. A deeper understanding of how neurovascular unit-related cells participate in NVC regulation is necessary to better understand blood flow and nerve activity recovery in cerebrovascular diseases.

Role of endothelial glycocalyx in central nervous system diseases and evaluation of the targeted therapeutic strategies for its protection: a review of clinical and experimental data

Central nervous system (CNS) diseases, such as stroke, traumatic brain injury, dementia, and demyelinating diseases, are generally characterized by high morbidity and mortality, which impose a heavy economic burden on patients and their caregivers throughout their lives as well as on public health. The occurrence and development of CNS diseases are closely associated with a series of pathophysiological changes including inflammation, blood-brain barrier disruption, and abnormal coagulation. Endothelial glycocalyx (EG) plays a key role in these changes, making it a novel intervention target for CNS diseases. Herein, we review the current understanding of the role of EG in common CNS diseases, from the perspective of individual pathways/cytokines in pathophysiological and systematic processes. Furthermore, we emphasize the recent developments in therapeutic agents targeted toward protection or restoration of EG. Some of these treatments have yielded unexpected pharmacological results, as previously unknown mechanisms underlying the degradation and destruction of EG has been brought to light. Furthermore, the anti-inflammatory, anticoagulative, and antioxidation effects of EG and its protective role exerted via the blood-brain barrier have been recognized.

A morphological post mortem profile in minor salivary glands changes in females

Women experience several systemic changes over all stages of life, many due to hormonal fluctuations. The sensation of dry mouth is the most common oral clinical symptom in women from climacteric period onwards, suggesting that sex hormones are important in maintaining salivary glands and oral homeostasis. Although the oral cavity is not conventional considered a target tissue for oestrogen, the extent to which salivary glands morphology and function are impacted by ageing and hormonal variations remain unknown. Due to the clinical demand for understanding oral changes related to the ageing process, this study aimed to portray the glandular morphological aspects in female during the different stages of life. To achieve this, 85 post-mortem specimens of labial minor salivary glands were obtained from females; they were distributed into three groups: group I (reproductive phase: up to 44 years, n = 18); group II (climateric phase: 45-55 years, n = 21) and group III (post-menopausal phase: over 56 years, n = 46). The most significant changes observed included degenerative parenchymal aspects including the replacement of parenchymal structures by fibrous tissue, inflammatory infiltrate as well as vascular and endothelial changes. Ageing was associated with acinar serous metaplasia (p = 0.011), acinar fibrosis (p = 0.042) and ductal ectasia (p = 0.003). The process of acinar atrophy was observed in all groups, with an increase in severity in group III. These degenerative aspects appear to be age-dependent.

Vascular Extracellular Matrix in Atherosclerosis

The extracellular matrix (ECM) plays a central role in the structural integrity and functionality of the cardiovascular system. Moreover, the ECM is involved in atherosclerotic plaque formation and stability. In fact, ECM remodeling affects plaque stability, cellular migration, and inflammatory responses. Collagens, fibronectin, laminin, elastin, and proteoglycans are crucial proteins during atherosclerosis development. This dynamic remodeling is driven by proteolytic enzymes such as matrix metalloproteinases (MMPs), cathepsins, and serine proteases. Exploring and investigating ECM dynamics is an important step to designing innovative therapeutic strategies targeting ECM remodeling mechanisms, thus offering significant advantages in the management of cardiovascular diseases. This review illustrates the structure and role of vascular ECM, presenting a new perspective on ECM remodeling and its potential as a therapeutic target in atherosclerosis treatments.

Unraveling neurovascular mysteries: the role of endothelial glycocalyx dysfunction in Alzheimer's disease pathogenesis

While cardiovascular disease, cancer, and human immunodeficiency virus (HIV) mortality rates have decreased over the past 20 years, Alzheimer's Disease (AD) deaths have risen by 145% since 2010. Despite significant research efforts, effective AD treatments remain elusive due to a poorly defined etiology and difficulty in targeting events that occur too downstream of disease onset. In hopes of elucidating alternative treatment pathways, now, AD is commonly being more broadly defined not only as a neurological disorder but also as a progression of a variety of cerebrovascular pathologies highlighted by the breakdown of the blood-brain barrier. The endothelial glycocalyx (GCX), which is an essential regulator of vascular physiology, plays a crucial role in the function of the neurovascular system, acting as an essential vascular mechanotransducer to facilitate ultimate blood-brain homeostasis. Shedding of the cerebrovascular GCX could be an early indication of neurovascular dysfunction and may subsequently progress neurodegenerative diseases like AD. Recent advances in in vitro modeling, gene/protein silencing, and imaging techniques offer new avenues of scrutinizing the GCX's effects on AD-related neurovascular pathology. Initial studies indicate GCX degradation in AD and other neurodegenerative diseases and have begun to demonstrate a possible link to GCX loss and cerebrovascular dysfunction. This review will scrutinize the GCX's contribution to known vascular etiologies of AD and propose future work aimed at continuing to uncover the relationship between GCX dysfunction and eventual AD-associated neurological deterioration.

Disruption of the endothelial glycocalyx layer is associated with idiopathic complete atrioventricular block in the elderly population: An observational pilot study

Idiopathic atrioventricular block (iCAVB) is the most common reason for the need for a permanent pacemaker in the elderly population. The fibrotic process that occurs in the conduction system of the heart with aging is the main pathogenesis in the development of iCAVB. However, the processes that trigger the development of iCAVB in the elderly population have not been fully elucidated. In this study, we aimed to reveal the possible relationship between the endothelial glycocalyx (EG) layer and idiopathic complete atrioventricular block. A group of 68 consecutive patients who developed iCAVB and a group of 68 healthy subjects matched for age, sex, and cardiovascular risk factors were included in the study. The groups were compared for clinical, laboratory, and levels of Syndecan-1 (SDC1), an EG layer marker. In the study, SDC1 levels were found to be significantly higher in the iCAVB group compared to the control group (23.7 ± 7.5 vs 16.7 ± 5.2; p = 0.009). In multivariable regression analysis, SDC1 was determined as an independent potential predictor for iCAVB (OR: 1.200; 95% CI: 1.119-1.287; p < 0.001). In the receiver operating characteristic curve analysis, SDC1 predicted iCAVB with 74% sensitivity and 72% specificity at the best cut-off value of 18.5 ng/mL (area under the curve: 0.777; confidence interval: 0.698-0.856; p < 0.001). Disruption of the endothelial glycolic layer may be one of the main triggering factors for the process leading to iCAVB.