Young blood-mediated cerebromicrovascular rejuvenation through heterochronic parabiosis: enhancing blood-brain barrier integrity and capillarization in the aged mouse brain

Functional ultrasound imaging reveals microvascular rarefaction, decreased cerebral blood flow, and impaired neurovascular coupling in a mouse model of paclitaxel-induced chemobrain

Chemotherapy-induced cognitive impairment (CICI), often referred to as "chemobrain," significantly affects the quality of life in cancer survivors. Although traditionally attributed to neuronal toxicity, emerging evidence suggests a key role of cerebrovascular dysfunction in its pathogenesis. We hypothesized that paclitaxel (PTX, Taxol) treatment induces long-term cerebrovascular dysfunction, including microvascular rarefaction, impaired neurovascular coupling (NVC), and altered cerebral blood flow (CBF), which contribute to CICI. Using a clinically relevant PTX treatment regimen in non-tumor-bearing mice, we evaluated the long-term effects of PTX on cerebrovascular health. Ultrasound localization microscopy (ULM) and functional ultrasound imaging (fUS) were employed to assess microvascular density, CBF, and NVC. PTX treatment resulted in a significant reduction in microvascular density in the cerebral cortex and hippocampus, key regions involved in cognitive function. PTX significantly reduced blood velocity in the middle cerebral artery. Moreover, PTX impaired NVC responses, as evidenced by a diminished CBF increase in response to whisker stimulation, indicative of impaired reactive hyperemia. In conclusion, these findings demonstrate that PTX induces long-lasting cerebrovascular dysfunction, including microvascular rarefaction, impaired NVC, and altered CBF dynamics, which likely contribute to CICI. This study underscores the critical role of cerebrovascular health in cognitive function and highlights the potential of targeting cerebrovascular pathways as a therapeutic approach for mitigating chemotherapy-induced cognitive deficits.

Cerebromicrovascular senescence in vascular cognitive impairment: does accelerated microvascular aging accompany atherosclerosis?

Vascular cognitive impairment (VCI) is a leading cause of age-related cognitive decline, driven by cerebrovascular dysfunction and cerebral small vessel disease (CSVD). Emerging evidence suggests that cerebromicrovascular endothelial senescence plays an important role in the pathogenesis of VCI by promoting cerebral blood flow dysregulation, neurovascular uncoupling, blood-brain barrier (BBB) disruption, and the development of cerebral microhemorrhages (CMHs). This review explores the concept of cerebromicrovascular senescence as a continuum of vascular aging, linking macrovascular atherosclerosis with microvascular dysfunction. It examines the mechanisms by which endothelial senescence drives neurovascular pathology and highlights the impact of cardiovascular risk factors in accelerating these processes. We examine preclinical and clinical studies that provide compelling evidence that atherosclerosis-induced microvascular senescence exacerbates cognitive impairment. In particular, findings suggest that targeting senescent endothelial cells through senolytic therapy can restore cerebrovascular function and improve cognitive outcomes in experimental models of atherosclerosis. Given the growing recognition of microvascular senescence as a therapeutic target, further research is warranted to explore novel interventions such as senolytics, anti-inflammatory agents, and metabolic modulators. The development of circulating biomarkers of vascular senescence (e.g., senescence-associated secretory phenotype [SASP] components and endothelial-derived extracellular vesicles) could enable early detection and risk stratification in individuals at high risk for VCI. Additionally, lifestyle modifications, including the Mediterranean diet, hold promise for delaying endothelial senescence and mitigating cognitive decline. In conclusion, cerebromicrovascular senescence is a key mechanistic link between atherosclerosis and cognitive impairment. Addressing microvascular aging as a modifiable risk factor through targeted interventions offers a promising strategy for reducing the burden of VCI and preserving cognitive function in aging populations.

Systemic Rejuvenating Interventions: Perspectives on Neuroinflammation and Blood-Brain Barrier Integrity

The aging process results in structural, functional, and immunological changes in the brain, which contribute to cognitive decline and increase vulnerability to neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and stroke-related complications. Aging leads to cognitive changes and also affect executive functions. Additionally, it causes neurogenic and neurochemical alterations, such as a decline in dopamine and acetylcholine levels, which also impact cognitive performance. The chronic inflammation caused by aging contributes to the impairment of the blood-brain barrier (BBB), contributing to the infiltration of immune cells and exacerbating neuronal damage. Therefore, rejuvenating therapies such as heterochronic parabiosis, cerebrospinal fluid (CSF) administration, plasma, platelet-rich plasma (PRP), and stem cell therapy have shown potential to reverse these changes, offering new perspectives in the treatment of age-related neurological diseases. This review focuses on highlighting the effects of rejuvenating interventions on neuroinflammation and the BBB.

Chronic β3 adrenergic agonist treatment improves neurovascular coupling responses, attenuates blood-brain barrier leakage and neuroinflammation, and enhances cognition in aged mice

Microvascular endothelial dysfunction, characterized by impaired neurovascular coupling, reduced glucose uptake, blood-brain barrier disruption, and microvascular rarefaction, plays a critical role in the pathogenesis of age-related vascular cognitive impairment (VCI). Emerging evidence points to non-cell autonomous mechanisms mediated by adverse circulating milieu (an increased ratio of pro-geronic to anti-geronic circulating factors) in the pathogenesis of endothelial dysfunction leading to impaired cerebral blood flow and cognitive decline in the aging population. In particular, age-related adipose dysfunction contributes, at least in part, to an unfavorable systemic milieu characterized by chronic hyperglycemia, hyperinsulinemia, dyslipidemia, and altered adipokine profile, which together contribute to microvascular endothelial dysfunction. Hence, in the present study, we aimed to test whether thermogenic stimulation, an intervention known to improve adipose and systemic metabolism by increasing cellular energy expenditure, could mitigate brain endothelial dysfunction and improve cognition in the aging population. Eighteen-month-old C57BL/6J mice were treated with saline or β3-adrenergic agonist (CL 316, 243, CL) for 6 weeks followed by functional analysis to assess endothelial function and cognition. CL treatment improved neurovascular coupling responses and rescued brain glucose uptake in aged animals. In addition, CL treatment also attenuated blood-brain barrier leakage and associated neuroinflammation in the cortex and increased microvascular density in the hippocampus of aged mice. More importantly, these beneficial changes in microvascular function translated to improved cognitive performance in aged mice. Our results suggest that β3-adrenergic agonist treatment improves multiple aspects of cerebromicrovascular function and can be potentially repurposed for treating age-associated cognitive decline.

Genomic instability and genetic heterogeneity in aging: insights from clonal hematopoiesis (CHIP), monoclonal gammopathy (MGUS), and monoclonal B-cell lymphocytosis (MBL)

Aging is a multifaceted process characterized by a gradual decline in physiological function and increased susceptibility to a range of chronic diseases. Among the molecular and cellular mechanisms driving aging, genomic instability is a fundamental hallmark, contributing to increased mutation load and genetic heterogeneity within cellular populations. This review explores the role of genomic instability and genetic heterogeneity in aging in the hematopoietic system, with a particular focus on clonal hematopoiesis of indeterminate potential (CHIP), monoclonal gammopathy of undetermined significance (MGUS), and monoclonal B-cell lymphocytosis (MBL) as biomarkers. CHIP involves the clonal expansion of hematopoietic stem cells with somatic mutations. In contrast, MGUS is characterized by the presence of clonal plasma cells producing monoclonal immunoglobulins, while MBL is characterized by clonal proliferation of B cells. These conditions are prevalent in the aging population and serve as measurable indicators of underlying genomic instability. Studying these entities offers valuable insights into the mechanisms by which somatic mutations accumulate and drive clonal evolution in the hematopoietic system, providing a deeper understanding of how aging impacts cellular and tissue homeostasis. In summary, the hematopoietic system serves as a powerful model for investigating the interplay between genomic instability and aging. Incorporating age-related hematological conditions into aging research, alongside other biomarkers such as epigenetic clocks, can enhance the precision and predictive power of biological age assessments. These biomarkers provide a comprehensive view of the aging process, facilitating the early detection of age-related diseases and hopefully enabling personalized healthcare strategies.

Sex-specific mechanisms in vascular aging: exploring cellular and molecular pathways in the pathogenesis of age-related cardiovascular and cerebrovascular diseases

Aging remains the foremost risk factor for cardiovascular and cerebrovascular diseases, surpassing traditional factors in epidemiological significance. This review elucidates the cellular and molecular mechanisms underlying vascular aging, with an emphasis on sex differences that influence disease progression and clinical outcomes in older adults. We discuss the convergence of aging processes at the macro- and microvascular levels and their contributions to the pathogenesis of vascular diseases. Critical analysis of both preclinical and clinical studies reveals significant sex-specific variations in these mechanisms, which could be pivotal in understanding the disparity in disease morbidity and mortality between sexes. The review highlights key molecular pathways, including oxidative stress, inflammation, and autophagy, and their differential roles in the vascular aging of males and females. We argue that recognizing these sex-specific differences is crucial for developing targeted therapeutic strategies aimed at preventing and managing age-related vascular pathologies. The implications for personalized medicine and potential areas for future research are also explored, emphasizing the need for a nuanced approach to the study and treatment of vascular aging.

Endothelial Colony-Forming Cells (ECFCs) in cerebrovascular aging: Focus on the pathogenesis of Vascular Cognitive Impairment and Dementia (VCID), and treatment prospects

Endothelial colony-forming cells (ECFCs), a unique endothelial progenitor subset, are essential for vascular integrity and repair, providing significant regenerative potential. Recent studies highlight their role in cerebrovascular aging, particularly in the pathogenesis of vascular cognitive impairment and dementia (VCID). Aging disrupts ECFC functionality through mechanisms such as oxidative stress, chronic inflammation, and cellular senescence, leading to compromised vascular repair and reduced neurovascular resilience. ECFCs influence key cerebrovascular processes, including neurovascular coupling (NVC), blood-brain barrier (BBB) integrity, and vascular regeneration, which are critical for cognitive health. Age-related decline in ECFC quantity and functionality contributes to vascular rarefaction, diminished cerebral blood flow (CBF), and BBB permeability-processes that collectively exacerbate cognitive decline. This review delves into the multifaceted role of ECFCs in cerebrovascular aging and underscores their potential as therapeutic targets in addressing age-related vascular dysfunctions, presenting new directions for mitigating the effects of aging on brain health.

Chronological versus immunological aging: Immune rejuvenation to arrest cognitive decline

The contemporary understanding that the immune response significantly supports higher brain functions has emphasized the notion that the brain's condition is linked in a complex manner to the state of the immune system. It is therefore not surprising that immunity is a key factor in shaping brain aging. In this perspective article, we propose amending the Latin phrase "mens sana in corpore sano" ("a healthy mind in a healthy body") to "a healthy mind in a healthy immune system." Briefly, we discuss the emerging understanding of the pivotal role of the immune system in supporting lifelong brain maintenance, how the aging of the immune system impacts the brain, and how the potential rejuvenation of the immune system could, in turn, help revitalize brain function, with the ultimate ambitious goal of developing an anti-aging immune therapy.

Linking peripheral atherosclerosis to blood-brain barrier disruption: elucidating its role as a manifestation of cerebral small vessel disease in vascular cognitive impairment

Aging plays a pivotal role in the pathogenesis of cerebral small vessel disease (CSVD), contributing to the onset and progression of vascular cognitive impairment and dementia (VCID). In older adults, CSVD often leads to significant pathological outcomes, including blood-brain barrier (BBB) disruption, which in turn triggers neuroinflammation and white matter damage. This damage is frequently observed as white matter hyperintensities (WMHs) in neuroimaging studies. There is mounting evidence that older adults with atherosclerotic vascular diseases, such as peripheral artery disease, ischemic heart disease, and carotid artery stenosis, face a heightened risk of developing CSVD and VCID. This review explores the complex relationship between peripheral atherosclerosis, the pathogenesis of CSVD, and BBB disruption. It explores the continuum of vascular aging, emphasizing the shared pathomechanisms that underlie atherosclerosis in large arteries and BBB disruption in the cerebral microcirculation, exacerbating both CSVD and VCID. By reviewing current evidence, this paper discusses the impact of endothelial dysfunction, cellular senescence, inflammation, and oxidative stress on vascular and neurovascular health. This review aims to enhance understanding of these complex interactions and advocate for integrated approaches to manage vascular health, thereby mitigating the risk and progression of CSVD and VCID.

Microfluctuations in Capillary Lumens Independent of Pericyte Lining Density in the Anesthetized Mouse Cortex

OBJECTIVE

This study aimed to examine the spatiotemporal coherence of capillary lumen fluctuations in relation to spatial variations in the pericyte lining in the cortex of anesthetized mice.

METHODS

Two-photon microscopic angiography data (previously published) were reanalyzed, and spatial variations in capillary diameter fluctuations at rest and in capillary lining with vascular mural cells were measured along capillary centerlines.

RESULTS

Relatively large diameters of the capillaries (5.5 μm) coincided with a dense pericyte lining, while small capillaries (4.3 μm) had a sparse pericyte lining. Temporal variations had a frequency of about 0.1 Hz with an amplitude of 0.5 μm, which were negatively correlated with pericyte lining density. Spatial frequency analysis further revealed a common pattern of spatial variations in capillary diameter and pericyte lining, but temporal variations differed. The temporal variations in capillary lumens were locally distinct from those in neighboring locations, suggesting intrinsic fluctuations independent of the pericyte lining.

CONCLUSIONS

Capillary lumens in the brain exhibit slow microfluctuations that are independent of pericyte lining. These microfluctuations could affect the distribution of flowing blood cells and may be important for homogenizing their distribution in capillary networks.

Aging insights from heterochronic parabiosis models

Heterochronic parabiosis consists of surgically connecting the circulatory systems of a young and an old animal. This technique serves as a model to study circulating factors that accelerate aging in young organisms exposed to old blood or induce rejuvenation in old organisms exposed to young blood. Despite the promising results, the exact cellular and molecular mechanisms remain unclear, so this study aims to explore and elucidate them in more detail.

Chronic β3 adrenergic agonist treatment improves brain microvascular endothelial function and cognition in aged mice

Microvascular endothelial dysfunction, characterized by impaired neurovascular coupling, reduced glucose uptake, blood-brain barrier disruption, and microvascular rarefaction, plays a critical role in the pathogenesis of age-related vascular cognitive impairment (VCI). Emerging evidence points to non-cell autonomous mechanisms mediated by adverse circulating milieu (an increased ratio of pro-geronic to anti-geronic circulating factors) in the pathogenesis of endothelial dysfunction leading to impaired cerebral blood flow and cognitive decline in the aging population. In particular, age-related adipose dysfunction contributes, at least in part, to an unfavorable systemic milieu characterized by chronic hyperglycemia, hyperinsulinemia, dyslipidemia, and altered adipokine profile, which together contribute to microvascular endothelial dysfunction. Hence, in the present study, we aimed to test whether thermogenic stimulation, an intervention known to improve adipose and systemic metabolism by increasing cellular energy expenditure, could mitigate brain endothelial dysfunction and improve cognition in the aging population. Eighteen-month-old old C57BL/6J mice were treated with saline or CL (β3-adrenergic agonist) for 6 weeks followed by functional analysis to assess endothelial function and cognition. CL treatment improved neurovascular coupling responses and rescued brain glucose uptake in aged animals. In addition, CL treatment also attenuated blood-brain barrier leakage and associated neuroinflammation in the cortex of aged animals. More importantly, these beneficial changes in microvascular function translated to improved cognitive performance in radial arm water maze and Y-maze tests. Our results suggest that β3-adrenergic agonist treatment improves multiple aspects of brain microvascular endothelial function and can be potentially repurposed for treating age-associated cognitive decline.