Early Expression of Collagen Type I, III and IV and Matrix-Metalloproteinase(MMP)-2 mRNA in the Rat Bladder Subjected to Partial Outlet Obstruction

Lee, Ahnkie; Sung, Yeun Sun; Kim, Kwang Myung; Choi, Hwang; Kim, Shi Whang

Abstract

PURPOSE: Partial obstruction of the rat bladder outlet induces a rapid hypertrophy characterized by increased smooth muscle content and collagen deposition. This increased collagen is likely to reduce the quality of the contraction and compliance of the bladder wall. Also it has been reported that an alteration in the ratio of type I and III collagen may be more important than the amount of collagen in determining compliance. To evaluate the genetic basis of collagen deposition in the partially obstructed rat bladder, the author observed the change of proalpha1(I) collagen, proalpha1(III) collagen, proalpha(IV) collagen and matrix-metalloproteinase(MMP)-2 mRNA after partial urethral obstruction.
MATERIALS AND METHODS
Female Sprague-Dawley rats weighing 150-200g were used. Individual bladders were obtained from unoperated rats, and from rats at 6, 12, 48, 72, hours, 5 and 7 days after partial urethral obstruction and sham operation. Total RNA was extracted from each of these tissue, The expression of mRNAs were assessed by Northern blot analysis. The band intensities of the autoradiographs measured by densitometry were compared between the obstructed and sham group.
RESULTS
Partial urethral obstruction induced a gradual increase in bladder weights, The expression of mRNA for proalpha1(I) collagen was generally attenuated within 24hours after obstruction. In extended period of obstruction, the expression of mRNA for proalpha1(I)collagen reached a peak at day 3-5(219% increase), and remained elevated through day 7. The expression of mRNA for proalpha1(I)collagen was coregulated with that of pro alpha1(I) collagen, however, the mean ratio to control value of band intensity for proalpha1(III)collagen mRNA was 2 times higher than that of proalpha1(I) collagen, during days 3-7. The expression of mRNA for proalpha1(IV)collagen showed a sharp increase at 48 hours(438% increase)after obstruction earlier than proalpha1(I)collagen and proalpha1(III)collagen mRNA. In extended period of obstruction the expression reached a peak at 72 hours(883% increase) and the mean ratio to control value of band intensity for proalpha alpha collagen mRNA was much higher than those of proalpha1(I) collagen and proalpha1(III) collagen. The expression of MMP-2 mRNA increased from 48hours after obstruction, and reached a peak at day 3-5.
CONCLUSIONS
These results sugges that the increase of collagen in the rat bladder after partial urethral obstruction results from an increase of expression of collagen genes, and the decrease of bladder wall compliance results from an increased transcription of type I collagen gene and increase of the ratio of proalpha1(III)collagen to proalpha1(I)collagen mRNA. Because expression of proalpha1(I), (III), (IV) collagen and MMP-2 mRNA increased sharply after 48hours, it is suggested that genetic events leading to remodeling of bladder start at 48hours after partial urethral obstruction.