Selective Inhibition of Insulin Growth-Like Factor Receptor (IGFR) on Brain Endothelial Cells (BMECs) Using Adeno-Associated Virus (AAV) Serotype 9

Abstract

Ischemic stroke is the 5th leading cause of death within the U.S. and a major cause of long-term disability, especially in older females in comparison to men and younger women. This phenomenon is associated with a decrease in several steroid hormones including estrogen and the peptide hormone insulin growth-like factor (IGF)-1.1 In animal models, age-related loss of IGF-1 is associated with an increase in BBB permeability and worse stroke outcomes, including larger infarct volumes, greater sensory motor impairment, and increased neuroinflammation. Exogenous treatments of IGF-1 is shown to decrease BBB permeability and reduce brain infarct volume in middle-age female rats.8 Two main components of the BBB are astrocytes and brain microvessel endothelial cells (BMECs). Our recent studies demonstrated that targeted increases in IGF-1 expression in astrocytes through AAV-mediated gene transfer improves stroke outcomes in middle-age rats.10 These findings suggest that secreted astrocytic IGF-1 may act on endothelial cells to maintain the integrity of the blood brain barrier. To test this hypothesis, we propose to block IGF-1 receptors (IGFR) in BMECs of young female rats that still produce normal amounts of IGF-1. By successfully doing so, we would then be able to understand the significance of IGF-1 signaling on stroke outcomes as it interacts with BMECs. Adeno-associated virus (AAV) serotype 9, packaged with IGF1R shRNA and a mCherry reporter gene, was used to suppress the receptor. Mature adult female rats (5mo old) were injected with the control and siRNA containing AAV-9 vector. Integration of viral contents was assessed by immunohistochemistry and qPCR for IGFR on brain microvessels.