Poster #33 - Sangeeta Shukla

Neonatal Microglia Replacement: Monocyte-Derived Cells Rescue Seizure Phenotypes While Embryonic Microglia Exacerbate Them

Sangeeta Shukla1, Carleigh A. O'Brien2, Samuelle A. S. Delcy3, Eli M. Levitt2, Akiva S. Cohen4,5, Mariko L. Bennett6, Frederick C. Bennett2,6 1 The Department of Biomedical and Health Informatics, The Children's Hospital of Philadelphia, Philadelphia PA, USA, 19104. 2 Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA, 19104. 3 University of Pennsylvania, Perelman School of Medicine, Pharmacology Graduate Group. 4 Department of Anesthesiology and Critical Care Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA, 19104. 5 Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, USA, 19104. 6 Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA, USA, 19104.

Early-life microglia replacement-the depletion of endogenous microglia followed by the adoptive transfer of donor macrophages-has emerging therapeutic potential for pediatric neurological disorders; however, its long-term effects on neural circuits remain poorly understood. Using pharmacologic (PLX3397) and genetic (Cx3cr1-CreER; Csf1R fl/fl) models, we show that neonatal microglia depletion increases adult seizure severity, mortality, and neuropathology in a kainic acid-induced seizure model. Unexpectedly, transplantation of monocyte-derived microglia (mo-microglia) rescued these phenotypes, whereas transplantation of embryonically derived microglia (em-microglia) did not and even exacerbated outcomes. Bulk RNA-sequencing revealed ontogeny-dependent transcriptional responses to excitotoxic challenge, with transplanted em-microglia displaying prolonged inflammatory and stress-related gene expression, while mo-microglia upregulated immune-inhibitory, wound healing, and synaptic regulation pathways. Differential expression analysis identified seizure-exclusive gene signatures implicating macrophage origin as a key determinant of functional outcome. These findings attest to the importance of donor cell ontogeny in microglia replacement strategies and provide mechanistic insight for optimizing therapeutic approaches.