Fig. 1.

Characterization of cells that generate fibrillar collagen-Iα1 protein in models of kidney disease. A: split panel low-power confocal image of kidney cortex from Coll-GFP^Tg mouse d10 after ureteral obstruction to model inflammation and fibrosis, showing green fluorescent protein (GFP) nuclear and cytoplasm fluorescence of cells that are making collagen, colabeled with directly Cy3-conjugated anti-α-smooth muscle actin (α-SMA) antibodies. Note almost complete overlap (a, arteriole; g, glomerulus). B and C: high-power images of diseased kidney cortex from Coll-GFP^Tg mouse showing CD45⁺ leukocytes or S100A4⁺ cells. Note there is no overlap with collagen-producing cells. D: high-power image of single cells from a digested fibrotic Coll-GFP^Tg kidney showing that >99.9% of CD45⁺ cells do not generate collagen-Iα1 protein whereas a minority (<0.1%) do generate this protein weakly. E and F: images and graphs relating to bone marrow chimera mice in which only bone marrow cells harbor the Coll-GFP^Tg. E: diseased kidneys from these mice show rare bone marrow-derived cells restricted to perivenular sites that generate collagen protein (i.e., “circulating fibrocytes”) and lack the myofibroblast marker αSMA. F: number of fibrocytes/whole sagittal section (top) in mice with kidney disease in spleen and kidney, ± systemic injection of LPS (6 μg/g body wt). Percentage fibrocytes compared with leukocytes or myofibroblasts (bottom) in diseased kidney sections. Note that kidney circulating fibrocytes are exceptionally rare and are not increased after LPS whereas splenic fibrocytes are also rare, but more abundant and increased by LPS treatment. Bars, 25 μm.