Figure 4. Origin of fibroblasts during fibrosis and its reversal by BMP-7.

(A) Different sources of fibroblasts in organ fibrosis. Four possible mechanisms are depicted. One study suggests that about 12% of fibroblasts are from bone marrow, about 30% can arise via local EMT involving tubular epithelial cells under inflammatory stress, and about 35% are from EndMT (1). The remaining percentage likely emerge via proliferation of the resident fibroblasts and other still unidentified sources. (B) Systemic treatment of mice with renal fibrosis with recombinant human BMP-7 reverses renal disease due to severe attenuation of the formation of EMT- and EndMT-derived fibroblasts.