Microglia express Tie2 in a longitudinal imaging study of acute neural injury in mice.

The Tie2 receptor tyrosine kinase is expressed both in stroke recovery and cancer progression by vascular endothelial and myeloid lineage cells. Tie2 mechanisms have been described in vascular maturation, but the receptor's immune role remains poorly understood. Here, we describe the expression of Tie2 in microglia in response to an acute neural injury, uncovering a potential new role for these cells. Using magnetic resonance imaging (MRI) and the Ts-Biotag multimodal reporter mouse, we noninvasively imaged Tie2 expression dynamics in a longitudinal study of neural injury to identify key timepoints in wound signaling and healing. Using labeled bone marrow chimeras, we further determined that Tie2 is expressed in brain-resident microglia but not invading macrophages. Our results establish the utility of noninvasive molecular imaging for longitudinal studies of neuroimmune function and present a new role for Tie2 as a uniquely expressed marker of microglial function during wound healing.