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. Author manuscript; available in PMC: 2024 Jan 10.
Published in final edited form as: Immunity. 2022 Dec 14;56(1):58–77.e11. doi: 10.1016/j.immuni.2022.11.013

Figure 5. TREM2 is essential for macrophage efferocytosis of lipid-laden apoptotic hepatocytes.

Figure 5.

(A) KEGG pathway enrichment analysis of differentially expressed genes in Trem2−/− (n = 3) and WT (n = 4) BMDMs.

(B) Heatmap of phagocytosis related genes (GO:0006909) that were downregulated in Trem2−/− (n = 3) BMDMs compared to WT (n = 4) BMDMs.

(C) IPA of phagocytosis related functions in liver macrophages isolated from WD fed Trem2F/F and Trem2ΔMye mice. n = 4 mice per group.

(D) GSEA reveals phagosome related genes are enriched in primary liver macrophages isolated from Trem2F/F mice compared to Trem2ΔMye mice after WD feeding. n = 4 mice per group.

(E) Representative TUNEL staining of liver sections from Trem2F/F and Trem2ΔMye mice fed with WD for 8 weeks (n = 8 mice per group).

(F) Immunoblot analysis of aCasp3 (cleaved caspase-3), Casp3 (caspase-3), and GAPDH in liver tissue from Trem2F/F and Trem2ΔMye mice fed with WD for 8 weeks (n = 3 mice per group).

(G) BMDMs (left panel) or primary liver macrophages (right panel) from Trem2F/F and Trem2ΔMye mice were cocultured for 4 hours with AML12 cells that were labeled with pHrodo™ Red and treated with PA to induce apoptosis. Flow cytometry analysis of TREM2 and pHrodo™ Red was then performed for assessing the efficacy of macrophage efferocytosis of apoptotic hepatocytes.

(H) PA-treated apoptotic AML12 cells were cocultured with Trem2F/F and Trem2ΔMye BMDMs for 2 hours. n = 6 per group.

(I) PA-treated apoptotic AML12 cells were cocultured with WT BMDMs that were pretreated with either TREM2 neutralizing antibody (Anti-TREM2, 200 ng/ml) or an isotype control antibody (IgG2B). n = 6 per group.

(J) PA-treated primary hepatocytes were cocultured with primary liver macrophages from C57BL/6 mice. n = 6 per group.

(K) WT BMDMs were cocultured with AML12 cells that were treated with PA to induce apoptosis followed by incubation with recombinant sTREM2 (200 ng/ml). n = 6 per group.

Scale bar, 100μm. Efferocytosis was quantified as the percentage of BMDMs engulfing apoptotic AML12 cells. Data are shown as mean ± s.e.m.. **p<0.01; ***p<0.001. All in vitro experiments were repeated independently at least three times. See also Figure S5, Video S1, and Video S2.