Single-cell RNA-sequencing of skin immune cells uncover a role for Angptl4-mediated ifi20b expression in monocyte cell fate differentiation during wound healing

Angiopoietin-like protein 4 (Angptl4) is a matricellular protein that associates with extracellular matrix proteins, mediating complex cell-cell, and cell-matrix interactions. It has been implicated in various inflammation-associated diseases, including wound healing, but very few reports describe a direct role for Angptl4 in the immune landscape of wound microenvironment. Here, we studied whether Angptl4 regulates the immune response during wound healing. Using single-cell RNA sequencing to examine the temporal changes in the immune cell landscape of excisional wounds from wild type and Angplt4-knockout (Angplt4-/-) mice revealed that Angptl4-/- wounds had a stalled inflammatory phase. Infiltrated neutrophils remained elevated in the Angptl4-/- wounds due to an impaired monocyte to macrophage differentiation needed for clearance. The impaired monocyte differentiation was also validated in wounds using multi-color flow cytometry. Pairwise comparisons of differentially expressed genes from wound-derived and bone-marrow derived macrophages demonstrated few differences, suggesting that Angptl4 has a confined regulome. We identified interferon activated protein 202B (ifi202b) to be consistently upregulated in Angptl4-/- macrophages. . Pathway analysis further confirmed that ifi202b significantly impacted multiple gene networks involved in the cell fate of monocytes and the functions of monocyte-derived macrophages. Taken altogether, we conclude that Angptl4 orchestrates the inflammatory state, innate immune landscape, and healing process in the wound microenvironment via its transcriptional regulation on ifi202b. Single cell RNA-sequencing of the immune cells isolated from excisional wounds on wildtype and Angptl4-knockout mice at 1- and 5-days post wounding