Estrogen modulation of spinal cord microglia for respiratory neuroplasticity

PROJECT SUMMARY Stimulation of beneficial neuroplasticity is a crucial component in promoting recovery from neurological diseases

or insults like spinal cord injury and stroke. Respiratory neuroplasticity, in the form of phrenic long-term facilitation (pLTF), can be induced non-pharmacologically via acute intermittent hypoxia (AIH). However, it is abolished in conditions of low circulating sex hormones or elevated systemic inflammation. At present, the interaction of sex

hormones, CNS inflammation, and mechanisms of neuroplasticity are not well understood. The long-term objectives of this research are to understand the mechanism of microglial-mediated inflammation in cases of reduced circulating estrogen. Our central hypothesis is that reduced levels of circulating estrogen provoke a

microglial-mediated increase in inflammatory cytokine gene and protein expression in the spinal cord, accompanied by altered microglial morphology, which inhibits plasticity. The hypothesis will be tested through two specific aims. 1: Define the inflammatory cytokine signature of the ventral cervical spinal cord of

female rats across estradiol states. The approach for this aim will involve assessment of inflammatory-related gene and protein changes in the ventral cervical spinal cord of female rats using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and multi-color flow cytometry, respectively. Further, we will determine if

cytokine changes are driven by spinal microglia by assessing isolated microglia from ventral cervical spinal cords of ovariectomized and naturally cycling female rats. 2: Determine the role of spinal cord microglia in modulating the expression of phrenic neuroplasticity in states of reduced estradiol. The approach for this

aim will be to apply three dimensional Sholl analysis to cervical spinal cord segment images to allow quantification of altered microglial morphology across low and high states of circulating estradiol. Multi-color flow cytometry will be used to quantify microglial proliferation. Secondly, female rats will be treated with a CSF1R

inhibitor to transiently eradicate CNS microglial populations. AIH-induced pLTF will be measured via in vivo phrenic neurophysiology. This proposed research will contribute to science by establishing the mechanistic role and molecular signature of spinal microglia in inhibiting plasticity in states of low estradiol. These contributions

are expected to be significant in advancing neuroplasticity research because they will support the need to account for sexual dimorphisms when designing and implementing novel neurotherapeutic interventions. The proposed research is part of a fellowship training plan with extensive hands-on training and mentoring in technical

and professional research skills necessary to become an independent clinician-researcher. Primary research activities and training will take place at the University of Minnesota Medical School with additional training at the University of Wisconsin – Madison. The University of Minnesota’s strong foundation in research and the support

of the Rehabilitation Science graduate program will create an ideal environment for completing this training.