NR4A1 and fibrosis: The mere fact that cardiomyocyte-specific Nur77 deficient mice, the CM-KO, develop increased cardiac fibrosis to the same extent as whole-body Nur77-KO mice, but that only the Nur77-KO hearts show an aberrant collagen fiber structure, made us the reason that Nur77 is involved in regulating the interplay between (myo)fibroblasts and cardiomyocytes in fibrosis.