Correlation between prenatal urinary matrix metalloproteinase activity and the degree of kidney damage in a large animal model of congenital obstructive uropathy.

BACKGROUND/PURPOSE: We aimed to determine whether the profile of matrix metalloproteinase (MMP) activity in fetal urine correlates with the degree of kidney damage in the setting of congenital obstructive uropathy. METHODS: Fetal lambs underwent either a sham operation or creation of a complete urinary tract obstruction. Necropsies were performed before term, when urinary MMP profiling was performed by zymography; and kidney damage was assessed histologically by multiple semiquantitative analyses and histomorphometric measurements. RESULTS: There was a significant correlation between inner medullary thickness and MMP-9 (P = .005) and 63-kd MMP-2 (P = .019) activities. In like manner, the only MMPs associated with kidney fibrosis were MMP-9 and 63-kd MMP-2. Matrix metalloproteinase-9 activity was a highly significant independent predictor of the total combined kidney fibrosis score (P < .001) as well as of higher fibrosis grades in each of 6 kidney areas analyzed (all with P < .01). The activity of 63-kd MMP-2 correlated significantly with higher fibrosis in select areas. CONCLUSIONS: In a fetal ovine model, urinary MMP activity correlates with the degree of kidney damage. The presence of MMP-9 (in particular) and that of 63-kd MMP-2 are independent predictors of severity. Prenatal urinary MMP profiling may enhance patient stratification and counseling in the setting of congenital obstructive uropathy.