Attenuation of renal morphological injury and interstitial matrix deposition in obstructive nephropathy in mice lacking tPA. Representative micrographs show kidney morphology (a and b), collagen III (c and d), and fibronectin (e and f) deposition at 7 days after ureteral obstruction in tPA^+/+ (a, c, and e) and tPA^–/– (b, d, and f) mice. No appreciable difference in renal morphology and matrix deposition was observed in the kidneys of either sham-operated or UUO mice after 3 days between these two genotypes (not shown). However, significant reduction in morphological injury and interstitial matrix deposition was found at 7 days after UUO in the obstructed kidneys of tPA^–/– mice. The deposition of interstitial matrix components collagen III and fibronectin was shown by indirect immunofluorescence staining using specific antibodies. Scale bar, 20 μm.