CCL2 and myalgic encephalomeyelitis/chronic fatigue syndrome: In the pathogenesis of CFs activation and cardiac fibrosis, it has been observed and recorded that the endogenous component is the modification in the matrix structure or composition, the induction of multiple growth factors and cytokines [such as TGF-β, connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF), Ang II, endothelin-1], the increase of mechanical stress, the upregulation of inflammatory signaling and chemokines [such as TNF-α, IL-1β, IL-6, C-C motif chemokine ligand 2 (CCL2)] (Frangogiannis, 2004; Kong et al., 2014; Schaefer, 2018).