Date of Award

January 2023

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)



First Advisor

Lloyd Cantley


Background: Following kidney injury, macrophages that have infiltrated the kidney undergo a transition from an initial proinflammatory state to a pro-reparative one characterized by the expression of arginase-1 (Arg 1), mannose receptor (Mrc1) and macrophage scavenger receptor-1 (Msr1). Granulocyte-macrophage colony-stimulating factor (GM-CSF) is an essential tubular-cell-derived determinant of the pro-reparative phenotype. However, it remains unclear what additional, if any, signals macrophages are integrating to maximally induce arginase-1.

Hypothesis: (1) The addition of cellular debris as a tubular cell cast mimetic will augment Arg1 expression in GM-CSF stimulated bone marrow derived macrophages; (2) Toll-like-receptors 2/4 transduce the debris signal from (1) and serve as the co- stimulatory signal in concert with GM-CSF to increase Arg1 expression.

Methods: Wildtype and TLR 2/4 knock-out macrophages were cultured in the presence of GM-CSF in the presence or absence of tubular cell debris to determine the relative expression of arginase-1 in macrophages.

Results: In cultured macrophages exposed to GM-CSF, the addition of cellular debris showed a significantly higher mRNA expression of Arg1, sometimes comparable to macrophages cultured with primary cultured renal cells (PCRC) with apical debris mimicking tubular casts. TLR 2/4 KO macrophages had an abrogation of Arg1 mRNA expression relative to wildtype macrophages cultured with GM-CSF and debris. However, no difference in levels of Mrc1 expression was seen.


This is an Open Access Thesis.

Open Access

This Article is Open Access