Effect of C1q-CD44 interactions on microglial phagocytosis 9379

Abstract Description Spinal cord injuries (SCI) are debilitating, lifelong, and impact an estimated 15,000 people per year in the United States alone. As the resident immune cells of the brain, microglia clear dead cells and debris from the injury epicenter, which is essential for recovery. However, the mechanisms regulating microglial phagocytosis after SCI remain only partly understood. Complement protein C1q is present at high levels in the injury epicenter and is known to tag debris for phagocytosis by microglia. Our lab recently identified five novel C1q receptor candidates, including CD44, an established phagocytic receptor. Based on CD44’s established role in modulating macrophage phagocytosis, I hypothesize that C1q-CD44 interactions can modulate microglial phagocytosis. To test this, CD44 wild-type (WT) and knockout (KO) induced pluripotent stem cell-derived microglia (iMGL) were treated with C1q[200 nM] and pHrodo particles which fluoresce upon lysosome internalization. Particle internalization was validated using fluorescence microscopy, and quantification of the proportion of microglia exhibiting phagocytosis of pHrodo in the presence or absence of C1q was performed by flow cytometry. I found that CD44 KO iMGL phagocytose at elevated levels when compared to WT iMGL, indicating that CD44 is a crucial regulator of microglial phagocytosis. Overall, characterization of C1q-CD44 interactions can inform therapeutic development for SCI. Funding Sources Funded by the California Institute for Regenerative Medicine under Award Number EDUC5-13637. Topic Categories Neuroimmunology (NEUR)