Blood vessels, from arteries to capillaries to venules and then to veins, contribute to fundamental physiological processes. However, the vascular responses for repair and restoration of microvascular networks after cortical brain injury are poorly understood, including how neuronal activity influences these processes. A major barrier to research is the poor accessibility of micro-vessels in the brain and associated technical difficulties. To overcome this barrier, we propose to use innovative imaging technologies that we have co-developed to investigate micro-vessel formation and re-growth in response to focal cortical injury. We have used light-weight head-mounted, miniaturized microscopes (?miniscopes?) to dynamically image the vasculature and associated cells with high spatial and temporal resolution. We will use cortical injury models by applying a controlled moderate impact to the mouse motor cortex. Combining in vivo longitudinal miniscope and 2-photon imaging, histological ?vessel painting? and perfusion-weighted magnetic resonance imaging (PWI MRI), we aim to achieve a deeper understanding of microvascular restoration following cortical injury. We will apply targeted optogenetic stimulation of excitatory neurons and specific inhibitory neurons to modulate microvascular repair in early and late phases of vessel re-growth. Our guiding hypothesis is that microvascular restoration and remodeling after cortical injury are regulated by vascularization sequences and cellular processes that are similarly observed in normal vasculogenesis during central nervous system development.
In Aim 1, we will identify the time course and spatial pattern of vascular regrowth, and blood flow dynamics after focal cortical injury. Vascular networks and blood flow are visualized with fluorescent-labeled dextrans for in vivo imaging for quantitative measurements.
In Aim 2, we will determine the role of endothelial cells in new blood vessel sprouting and the establishment of functional microvascular by imaging Tie2-Cre reporter mice during the first two weeks post- injury. We will also examine the influence of astrocytes and pericytes in vascular re-growth.
In Aim 3, we will test the hypothesis that optogenetic stimulation of specific neuron types in a temporally controlled manner facilitates and enhances microvasculature restoration for post-injury repair. We will also examine if and how targeted modulation of neural activities modulate Wnt/-catenin and VEGF signaling mechanisms that are critical for micro-vessel re-growth. Behavioral testing will assess the outcomes of the optogenetic treatment. We have strong preliminary data that supports the premise for the proposed research for all aims. The proposed research will advance our understanding of the cellular and molecular mechanisms underlying cortical microvascular restoration and how neural stimulation enhances vascular network formation.
Vascular restoration processes are critical for improving neurological outcomes after brain injury. Using innovative imaging technologies, our proposed research will longitudinally track the vasculature and associated cells with high spatial and temporal resolution to assess the dynamic cellular processes that drive post-injury microvascular repair. Our results will help to develop new and effective therapeutic interventions and treatment for acquired brain injuries.
