POSTN and Myocardial fibrosis: MDMs have also been shown to promote fibroblast activator protein (FAP)/periostin (POSTN) signaling in fibroblasts within spatially defined niches via local release of IL-1β [36], and the deletion of either the IL-1 receptor on fibroblasts or the IL-1β ligand in MDMs reduces FAP/POSTN in fibroblasts, decreases myocardial fibrosis, and enhances cardiac function [36].