Capillary regression leads to sustained local hypoperfusion by inducing constriction of upstream transitional vessels.

In the brain, a microvascular sensory web coordinates oxygen delivery to regions of neuronal activity. This involves a dense network of capillaries that send conductive signals upstream to feeding arterioles to promote vasodilation and blood flow. Although this process is critical to the metabolic supply of healthy brain tissue, it may also be a point of vulnerability in disease. Deterioration of capillary networks is a feature of many neurological disorders and injuries and how this web is engaged during vascular damage remains unknown. We performed in vivo two-photon microscopy on young adult mural cell reporter mice and induced focal capillary injuries using precise two-photon laser irradiation of single capillaries. We found that ~59% of the injuries resulted in regression of the capillary segment 7 to 14 d following injury, and the remaining repaired to reestablish blood flow within 7 d. Injuries that resulted in capillary regression induced sustained vasoconstriction in the upstream arteriole-capillary transition (ACT) zone at least 21 days postinjury in both awake and anesthetized mice. The degree of vasomotor dynamics was chronically attenuated in the ACT zone consequently reducing blood flow in the ACT zone and in secondary, uninjured downstream capillaries. These findings demonstrate how focal capillary injury and regression can impair the microvascular sensory web and contribute to cerebral hypoperfusion.

Pericytes: Unsung heroes in myelin repair after neonatal brain hypoxia.

Preterm infants can face lasting neurodevelopmental challenges due to hypoxia-induced injury of the cerebral white matter. In this issue of Neuron, Ren et al.1 identify microvascular pericytes as unexpected targets for growth hormone signaling, which enhances angiogenesis and remyelination after hypoxic injury in the developing mouse brain.

Is CAA a perivascular brain clearance disease? A discussion of the evidence to date and outlook for future studies.

The brain's network of perivascular channels for clearance of excess fluids and waste plays a critical role in the pathogenesis of several neurodegenerative diseases including cerebral amyloid angiopathy (CAA). CAA is the main cause of hemorrhagic stroke in the elderly, the most common vascular comorbidity in Alzheimer's disease and also implicated in adverse events related to anti-amyloid immunotherapy. Remarkably, the mechanisms governing perivascular clearance of soluble amyloid ß-a key culprit in CAA-from the brain to draining lymphatics and systemic circulation remains poorly understood. This knowledge gap is critically important to bridge for understanding the pathophysiology of CAA and accelerate development of targeted therapeutics. The authors of this review recently converged their diverse expertise in the field of perivascular physiology to specifically address this problem within the framework of a Leducq Foundation Transatlantic Network of Excellence on Brain Clearance. This review discusses the overarching goal of the consortium and explores the evidence supporting or refuting the role of impaired perivascular clearance in the pathophysiology of CAA with a focus on translating observations from rodents to humans. We also discuss the anatomical features of perivascular channels as well as the biophysical characteristics of fluid and solute transport.

Alignment of Canada's COVID-19 policy response with barriers and facilitators for coping reported by caregivers of youth with developmental delays, disorders, and disabilities.

Introduction: The UNICEF-WHO Global Report on Developmental Delays, Disorders, and Disabilities is an ongoing initiative aimed at increasing awareness, compiling data, providing guidance on strengthening health systems, and engaging country-level partners. Data from its caregiver survey assessing impacts of the COVID-19 pandemic showed that half of youths with developmental delays and disabilities (DDDs) and their caregivers struggled to cope, with a significant portion reporting a lack of supports and difficulty managing the worsening of the child's symptoms in isolation. Governments created service strategies supporting vulnerable groups. Little is known about the alignment between COVID-19 policies for persons with disabilities and their lived experiences. Contextualizing caregivers' experiences can promote the development of tailored public supports for these families following a public health crisis. Methods: Online survey data were collected from June-July 2020, leading to a convenience sample of caregivers of youth with DDDs across Canada. Respondents answered two open-ended questions regarding challenges and coping strategies during the pandemic. We conducted a thematic analysis of responses using inductive coding on NVivo software. Overarching codes derived from the dataset were contextualized using an analysis of provincial policies published during the pandemic. Parallels with these policies supported the exploration of families' and youths' experiences during the same period. Results: Five hundred and seventy-six (N = 576) participants answered open-ended questions. Barriers to coping included family mental health issues, concerns about the youths' regression, challenges in online schooling, limited play spaces, and managing physical health during quarantine. Environmental barriers encompassed deteriorating family finances, loss of public services, and a lack of accessible information and supports. In contrast, caregivers reported coping facilitators, such as family time, outdoor activities, and their child's resilience. Environmental facilitators included community resources, public financial supports, and access to telehealth services. Few COVID-19 policies effectively addressed caregiver-identified barriers, while some restrictions hindered access to facilitators. Conclusion: Prioritizing needs of families of youths with DDDs during public health emergencies can significantly impact their experiences and mental health. Enhancing financial benefits, providing telehealth services, and creating inclusive public play spaces are priority areas as we navigate the post-pandemic landscape.

Impaired drainage through capillary-venous networks contributes to age-related white matter loss.

The gradual loss of cerebral white matter contributes to cognitive decline during aging. However, microvascular networks that support the metabolic demands of white matter remain poorly defined. We used in vivo deep multi-photon imaging to characterize microvascular networks that perfuse cortical layer 6 and corpus callosum, a highly studied region of white matter in the mouse brain. We show that these deep tissues are exclusively drained by sparse and wide-reaching venules, termed principal cortical venules, which mirror vascular architecture at the human cortical-U fiber interface. During aging, capillary networks draining into deep branches of principal cortical venules are selectively constricted, reduced in density, and diminished in pericyte numbers. This causes hypo-perfusion in deep tissues, and correlates with gliosis and demyelination, whereas superficial tissues become relatively hyper-perfused. Thus, age-related impairment of capillary-venular drainage is a key vascular deficit that contributes to the unique vulnerability of cerebral white matter during brain aging.

Does Perinatal Intermittent Hypoxia Affect Cerebrovascular Network Development?

Perinatal hypoxia is an inadequate delivery of oxygen to the fetus in the period immediately before, during, or after the birth process. The most frequent form of hypoxia occurring in human development is chronic intermittent hypoxia (CIH) due to sleep-disordered breathing (apnea) or bradycardia events. CIH incidence is particularly high with premature infants. During CIH, repetitive cycles of hypoxia and reoxygenation initiate oxidative stress and inflammatory cascades in the brain. A dense microvascular network of arterioles, capillaries, and venules is required to support the constant metabolic demands of the adult brain. The development and refinement of this microvasculature is orchestrated throughout gestation and in the initial weeks after birth, at a critical juncture when CIH can occur. There is little knowledge on how CIH affects the development of the cerebrovasculature. However, since CIH (and its treatments) can cause profound abnormalities in tissue oxygen content and neural activity, there is reason to believe that it can induce lasting abnormalities in vascular structure and function at the microvascular level contributing to neurodevelopmental disorders. This mini-review discusses the hypothesis that CIH induces a positive feedback loop to perpetuate metabolic insufficiency through derailment of normal cerebrovascular development, leading to long-term deficiencies in cerebrovascular function.

Evaluation of an adapted virtual training for master trainers of the WHO Caregiver Skills Training Program during the COVID-19 pandemic.

LAY ABSTRACT: The COVID-19 pandemic interrupted in-person professional activities. We developed and evaluated a remote training approach for master trainers of the Caregiver Skills Training Program. Master trainers support community practitioners, who in turn deliver the Caregiver Skills Training Program to caregivers of children with developmental delays or disabilities. The Caregiver Skills Training Program teaches caregivers how to use strategies to enhance learning and interactions during everyday play and home activities and routines with their child. The aim of this study was to evaluate the remote training of master trainers on Caregiver Skills Training Program. Twelve out of the 19 practitioners who enrolled in the training completed the study. The training consisted of a 5-day in-person session completed prior to the pandemic, followed by supporting participants' ability to identify Caregiver Skills Training Program strategies through coding of video recordings over 7 weekly meetings and group discussions and ended with participants independently coding a set of 10 videos for Caregiver Skills Training Program strategies. We found all but one participant was able to reliably identify Caregiver Skills Training Program strategies from video recordings despite a lack of ability to practice the Caregiver Skills Training Program strategies with children due to the pandemic. Taken together, our findings illustrate the feasibility and value of remote training approaches in implementing interventions.

Urban and rural differences in needs, service use and satisfaction among caregivers of autistic children in Morocco.

LAY ABSTRACT: It is very important to understand the needs of caregivers to be able to empower caregivers and to develop or improve services around the world. Therefore, research in different regions is needed to understand differences in caregivers needs between countries, but also between areas within countries. This study investigated differences in needs and service use between caregivers of autistic children in Morocco, living in urban and rural areas. A total of 131 Moroccan caregivers of autistic children took part in the study and responded to an interview survey. The results showed both similarities and differences between urban and rural living caregivers' challenges and needs. Autistic children from urban communities were much more likely to receive intervention and attend school than children from rural communities, even though age and verbal skills of the two groups of children were comparable. Caregivers expressed similar needs for improved care and education, but different challenges in caring. Limited autonomy skills in children were more challenging to rural caregivers, while limited social-communicational skills were more challenging to urban caregivers. These differences may inform healthcare policy-makers and program developers. Adaptive interventions are important to respond to regional needs, resources, and practices. In addition, the results showed the importance of addressing challenges as experienced by caregivers such as costs related to care, barriers in access to information, or stigma. Addressing these issues may help reduce both global and within-country differences in autism care.

The elusive brain perivascular fibroblast: a potential role in vascular stability and homeostasis.

In the brain, perivascular fibroblasts (PVFs) reside within the perivascular spaces (PVSs) of arterioles and large venules, however their physiological and pathophysiological roles remain largely unknown. PVFs express numerous extracellular matrix proteins that are found in the basement membrane and PVS surrounding large diameter vessels. PVFs are sandwiched between the mural cell layer and astrocytic endfeet, where they are poised to interact with mural cells, perivascular macrophages, and astrocytes. We draw connections between the more well-studied PVF pro-fibrotic response in ischemic injury and the less understood thickening of the vascular wall and enlargement of the PVS described in dementia and neurodegenerative diseases. We postulate that PVFs may be responsible for stability and homeostasis of the brain vasculature, and may also contribute to changes within the PVS during disease.

Capillary regression leads to sustained local hypoperfusion by inducing constriction of upstream transitional vessels.

In the brain, a microvascular sensory web coordinates oxygen delivery to regions of neuronal activity. This involves a dense network of capillaries that send conductive signals upstream to feeding arterioles to promote vasodilation and blood flow. Although this process is critical to the metabolic supply of healthy brain tissue, it may also be a point of vulnerability in disease. Deterioration of capillary networks is a hallmark of many neurological disorders and how this web is engaged during vascular damage remains unknown. We performed in vivo two-photon microscopy on young adult mural cell reporter mice and induced focal capillary injuries using precise two-photon laser irradiation of single capillaries. We found that ∼63% of the injuries resulted in regression of the capillary segment 7-14 days following injury, and the remaining repaired to re-establish blood flow within 7 days. Injuries that resulted in capillary regression induced sustained vasoconstriction in the upstream arteriole-capillary transition (ACT) zone at least 21 days post-injury in both awake and anesthetized mice. This abnormal vasoconstriction involved attenuation of vasomotor dynamics and uncoupling from mural cell calcium signaling following capillary regression. Consequently, blood flow was reduced in the ACT zone and in secondary, uninjured downstream capillaries. These findings demonstrate how capillary injury and regression, as often seen in age-related neurological disease, can impair the microvascular sensory web and contribute to cerebral hypoperfusion. SIGNIFICANCE: Deterioration of the capillary network is a characteristic of many neurological diseases and can exacerbate neuronal dysfunction and degeneration due to poor blood perfusion. Here we show that focal capillary injuries can induce vessel regression and elicit sustained vasoconstriction in upstream transitional vessels that branch from cortical penetrating arterioles. This reduces blood flow to broader, uninjured regions of the same microvascular network. These findings suggest that widespread and cumulative damage to brain capillaries in neurological disease may broadly affect blood supply and contribute to hypoperfusion through their remote actions.