Sunday, December 22, 2024
12/22/2024
The constriction and regression of brain capillaries is well documented in Alzheimer’s disease and Vascular Contributions to Cognitive Impairment and Dementia (AD/VCID). There is strong preclinical and clinical evidence to suggest that contraction of pericytes leads to abnormal capillary constriction, and that this contributes to cerebral hypoperfusion in AD/VCID. However, rigorous approaches to incorporate pericyte-driven hypoperfusion into AD/VCID models remain limited. This R61/R33 project will develop a novel chemogenetic model for cerebral hypoperfusion that involves adjustable control of CNS capillary flow by engaging pericyte contractile dynamics. We demonstrate feasibility of the approach by expressing in CNS pericytes, Gq-DREADDs (Designer Receptors Activated Only by Designer Drugs), an engineered G protein-coupled receptor that can be selectively and potently activated by ligands with little to no other biological activity. Using this “lock and key” approach, we achieved effective chemogenetic control of pericyte contractility and modulation of brain capillary flow and tissue oxygen levels in vivo. However, some limitations need to be overcome for broader utility of the model. Crossing Atp13a5-2A-CreER-IRES- tdTomato mice with floxed Gq-DREADD mice led to inefficient gene recombination with routine tamoxifen dosing, and the need to cross-breed mice becomes a burden for combining the hypoperfusion model with other disease models. Therefore, this project will develop Pericyte DREADD knock-in mice to circumvent the need for Cre-lox recombination. In the R61 phase, Pericyte Gq-DREADD mice will be created for chemogenetic contraction of brain pericytes in vivo. We will determine optimal dosing for systemic administration of DREADD agonist to achieve chronic blood flow reduction to ~50-75% of basal levels in adult and aged mice. Microvascular perfusion in gray and white matter will be assessed with longitudinal deep two-photon imaging and followed by detailed histology for hypoxic tissue damage and neuroinflammation. Conversely, Pericyte Gs-DREADD mice will be generated to relax CNS pericytes and dilation capillaries through chemogenetic inhibition. This tool can be used to rescue capillary perfusion in disease models where abnormal pericyte contraction has been implicated. If these initial studies are successful, the R33 phase will characterize the Pericyte Gq-DREADD hypoperfusion model by performing a battery of sensorimotor and cognitive tests. Longitudinal high-field MRI for cerebral blood flow and white matter integrity will be conducted. Single cell transcriptomic analysis will be used to map transcriptomic changes resulting from acute and chronic hypoperfusion. Finally, the new mice will be bred with established genetic models of amyloid β over-expression (TgSwDi) to test the hypothesis that capillary hypoperfusion worsens amyloid β deposition and augments pathology. Pericyte Gs-DREADDs will be crossed with TgSwDi mice to determine if age-related cerebral blood flow deficits can be ameliorated. After characterization, Pericyte Gq-DREADD and Gs-DREADD mice will be independently tested by collaborating laboratories and shared through the Jackson Laboratory and MODEL-AD centers.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).