Impact of chronic neuroendocrine stress on cerebrovascular architecture and astrocyte morphology

Stress and hypertension are leading causes for cerebrovascular dysfunction. Astrocytes are a key component of the neurovascular unit and are involved in regulation of both angioplasticity and vascular reactivity. We investigated the hypothesis that centrally induced chronic neuroendocrine stress would lead to changes in astrocyte morphology and altered cerebrovascular architecture. Prolonged upregulation of brain-derived neurotrophic factor (BDNF) in the paraventricular nucleus of the hypothalamus (PVN) has been shown to chronically activate all major stress pathways, including the sympathetic nervous system and the hypothalamus-pituitary-adrenal axis. Taking advantage of this mechanism, we created a novel chronic neuroendocrine stress model by subjecting male Sprague Dawley rats to bilateral PVN injections of AAV2 viral vectors expressing either BDNF or GFP (for control). Cortical and hippocampal vasculature and astrocyte GFAP immunoreactivity were analyzed 14 weeks after vector injections. Fixed coronal brain slabs (2mm) were subjected to iDiSCO tissue transparency protocol and immunolabeling (PECAM: blood vessels; GFAP: astrocytes; and NeuN: neurons). Z-stacks were imaged with a Nikon C2 confocal microscope. IMARIS software was used to generate 3D models of the vasculature and astrocytes. Euclidean distance mapping (EDM) was used to determine distribution of non-labeled space to nearest blood vessels or astrocyte processes. Additionally, in-house 3D image analysis was used to track blood vessel characteristics and density in relation neural layers. IMARIS analysis found no differences in overall cortical or hippocampal vascular and branch point densities and EDM analysis revealed similar spacing characteristics of blood vessels in both regions. However, we found shorter distances between astrocytes in the hippocampus of BDNF rats indicating higher astrocyte density. Our in-house analysis performed in relation to the outer CA neuronal layer showed a reduction in large diameter vessels and larger distances between vessels in the BDNF group, particularly within the region 200-350mm ventral from the CA neuronal layer. In summary, we demonstrated that our novel model of chronic neuroendocrine stress induced glial activation and alterations in cerebrovascular architecture. Interestingly, changes in the vascular network were only detected by using image analysis techniques that took into consideration the laminar nature of neurovascular structures, highlighting the importance of developing such analytic techniques. The observed reduction of larger vascular diameters in certain hippocampal regions may indicate compensatory changes in response to hypertension in our neuroendocrine stress model, whereas the larger gaps between vessels may indicate capillary rarefaction increasing susceptibility to hippocampal hypoperfusion. Funded by R01HL166464 and R03AG072016. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.