Date of Award

Spring 2026

Degree Type

Thesis

Department

Biological Sciences

Director of Thesis

Ashley Kalinski

Second Reader

Julianna Bennett

Abstract

Clearance of myelin debris is an essential step in nerve regeneration after injury in both the central nervous system (CNS) and peripheral nervous system (PNS), a process that is primarily carried out by macrophages. Failure to phagocytose and clear myelin can prolong inflammation and impair recovery. Sterile alpha and TIR motif-containing protein 1 (SARM1) is well researched as a regulator of axonal degeneration, yet its role in macrophages is still unclear. This study investigates how sarm1 deletion and cytokine signaling influence macrophage uptake and clearance of CNS and PNS myelin in vitro. Splenic macrophages isolated from wild-type (WT) and sarm1 knockout (KO) mice were cultured and polarized using pro-inflammatory (LPS) or anti-inflammatory (IL-4) immunostimulation. Pro-inflammatory conditions were expected to enhance phagocytic activity relative to anti-inflammatory conditions, and macrophages were expected to consume PNS myelin more efficiently than CNS myelin, reflecting known differences in immune signaling and regenerative responses between these systems.  Following polarization, cells were exposed to either CNS or PNS myelin for 24 hours. To distinguish between myelin uptake and clearance capacity, two experimental conditions were performed. In one condition, cells were fixed 24 hours following myelin exposure to assess initial phagocytosis. In the second, myelin-containing media was removed, and cells were allowed a 24-hour clearance period prior to fixation. Myelin uptake and intracellular lipid consumption were quantified using immunofluorescence imaging with F4/80 macrophage labeling and Oil-Red O staining to identify lipid-rich macrophages. Preliminary evidence suggests that sarm1 KO macrophages have delayed polarization, decreased myelin uptake, and longer lipid retention compared to WT macrophages. By examining how genetic regulation and inflammatory cues interact to shape macrophage behavior, this study works to clarify immune mechanisms relating to myelin clearance and nerve repair. These findings may inform therapeutic strategies targeting macrophage function to improve regeneration after trauma and demyelinating diseases.

First Page

1

Last Page

32

Rights

© 2026, Grace J. Bergeron

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