Cardiac (myo)fibroblasts modulate the migration of monocyte subsets

Abstract

Cardiac fibroblasts play an important role in the regulation of the extracellular matrix and are newly recognized as inflammatory supporter cells. Interferon (IFN)-gamma is known to counteract transforming growth factor (TGF)-beta 1-induced myofibroblast differentiation. This study aims at investigating in vitro how IFN-gamma affects TGF-beta 1-induced monocyte attraction. Therefore, C4 fibroblasts and fibroblasts obtained by outgrowth culture from the left ventricle (LV) of male C57BL6/j mice were stimulated with TGF-beta 1, IFN-gamma and TGF-beta 1 + IFN-gamma. Confirming previous studies, IFN-gamma decreased the TGF-beta 1-induced myofibroblast differentiation, as obviated by lower collagen I, III, alpha-smooth muscle actin (alpha-SMA), lysyl oxidase (Lox)-1 and lysyl oxidase-like (LoxL)-2 levels in TGF-beta 1 + IFN-gamma-versus TGF-beta 1-stimulated cardiac fibroblasts. TGF-beta 1 + IFN-gamma-stimulated C4 and cardiac fibroblasts displayed a higher CC-chemokine ligand (CCL) 2, CCL7 and chemokine C-X3-C motif ligand (Cx3CL1) release versus sole TGF-beta 1- stimulated fibroblasts. Analysis of migrated monocyte subsets towards the different conditioned media further revealed that sole TGF-beta 1- and IFN-gamma-conditioned media particularly attracted Ly6C(low) and Ly6C(high) monocytes, respectively, as compared to control media. In line with theses findings, TGF-beta 1 + IFN-gamma-conditioned media led to a lower Ly6C(low)/Ly6C(high) monocyte migration ratio compared to sole TGF-beta 1 treatment. These differences in monocyte migration reflect the complex interplay of pro-inflammatory cytokines and pro-fibrotic factors in cardiac remodelling and inflammation.