ABSTRACT Vitamin D deficiency (VDD) is linked to a number of non-skeletal chronic conditions, including cardiovascular disease, stroke, autoimmune disease, and dementia, which are leading causes of disability and death worldwide. VDD increases the risk and severity of stroke, likely because vitamin D regulates endothelial cell function, vascular response, and the innate and adaptive immune system. Numerous preclinical studies have focused on the role of vitamin D in acute stroke, but what is not known are the effects of VDD on the pathological progression of chronic cerebral hypoperfusion. Chronic cerebral hypoperfusion is a pervasive state of long-term cerebral blood flow insufficiency that can lead to white matter damage, neuroinflammation, stroke, and cognitive impairment. Here, we propose to utilize two animal models of chronic cerebral hypoperfusion, in combination with a vitamin D modified diet, to delineate the role of vitamin D in pathologies associated with reduced cerebral blood flow. Bilateral Carotid Artery Stenosis (BCAS) is a model of vascular dementia, which is associated with small vessel disease, blood-brain barrier (BBB) dysfunction, micro-infarcts, and cognitive impairment. The Internal Carotid Artery Stenosis (ICAS) mouse model was developed as part of my KL2 project focused on moyamoya syndrome, a cerebrovascular condition that leads to stroke and compensatory angiogenesis at the base of the brain. The ICAS model is associated with decreased vessel diameter, increased vascular endothelial growth factor (VEGF), BBB dysfunction, and inflammation. Our central hypothesis is that VDD increases the pathological severity of chronic cerebral hypoperfusion, through increased vascular dysfunction and chronic inflammation, and that vitamin D supplementation will attenuate these effects. To test these hypotheses, we propose two specific aims. Aim 1 will focus on hypoxia-induced angiogenesis and vessel wall pathology, via quantification of angiogenic markers, signaling pathways, vascular network density, and assessment of the various components of the vessel wall. Aim 2 will focus on identifying inflammatory T cell subtypes (e.g., Th17 cells) and quantification of associated cytokines and signaling pathways in the blood and brain tissue. All animals will be subjected to cognitive testing to measure the effects of vitamin D modification on functional outcome following chronic cerebral hypoperfusion. Collectively, we believe the studies pursued in this proposal will address several critical knowledge gaps, utilizing a collective approach to define the role of vitamin D in the pathological progression of chronic cerebral hypoperfusion. Results from this study will be broadly applicable to patients suffering from reduced cerebral blood flow, such as atherosclerosis, moyamoya syndrome, and vascular dementia. Future expanded studies utilizing vitamin D intervention represent a potentially novel therapeutic for these patients worldwide.

NARRATIVE The proposed research is relevant to public health because vitamin D deficiency is a worldwide problem that may contribute to the severity of chronic cerebral hypoperfusion, which leads to blood vessel abnormalities, ischemic stroke, vascular dementia, and other debilitating and costly complications for which there are few treatment options. Data that result from these studies will determine the angiogenic and inflammatory mechanisms regulated by vitamin D that contribute to cerebral pathology and cognitive impairment, using two mouse models of cerebral hypoperfusion. This knowledge could lead to new treatment options for cerebrovascular-related conditions.