Title

Molecular mechanisms of cervical and uterine extracellular matrix remodeling

Date of Award

1994

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biochemistry and Molecular Biology

First Committee Member

J. Frederick Jr. Woessner, Committee Chair

Abstract

It is proposed that extracellular matrix remodeling can be accomplished through changes in the relative composition of the matrix and/or degradation of components. Two models were used in the rat to investigate each possibility: cervical dilatation at birth and post-partum uterine involution, respectively. It has been suggested that the small dermatan sulfate proteoglycan, decorin, is important in the determination of the physical properties of the cervix via interaction with collagen fibers. The cDNA clone of rat decorin was isolated and sequenced; the core protein is almost entirely composed of leucine-rich repeats that are thought to be involved in protein-protein interactions. It was demonstrated by Kokenyesi and Woessner (Biol. Reprod. 42, 87-97, 1990) that the total cervical decorin content and the ratio of decorin to collagen correlate with the changes in cervical mechanical properties. It is shown here that upon induction of pre-mature labor, the changes in the cervical decorin content, and in particular the decorin to collagen ratio, are changed in the same way as at normal term. An increase in both the decorin mRNA levels and the uptake of sulfate into the production of glycosaminoglycan chains was observed, concurrent with the increase in decorin content during pregnancy. In addition, it is shown that the total amount of collagen mRNA in the 1 day post-partum cervix is less than 25% of that measured in the term cervix. Over the same time period, the total collagen content of the cervix does not decrease, while the inner circumference drops by 58% (op. cit.). Based on these data, it is suggested that the collagen present at term reorganizes, causing a decrease in tissue strength. The fact that the decorin content correlates with the changes in cervical properties, even in artificially induced softening, supports the hypothesis that decorin is at least partially responsible for the determination of collagen organization.The second aspect of the project involved the characterization of a matrix metalloproteinase, matrilysin, involved in uterine involution. Comparison of the cDNA sequences of rat matrilysin (previously called uterine metalloproteinase, or UMP) reported here, and human pump-1 demonstrated for the first time that the two enzymes are orthologous. It is shown that the rat matrilysin is capable of activating rat procollagenase at physiological concentrations. In addition, it is demonstrated that matrilysin has a broad substrate specificity, and several matrilysin cutting sites on the $\alpha$2 chain of type I collagen are identified by protein sequencing. One of these sites is the same as the collagenase cutting site. Inhibition of matrilysin by three synthetic inhibitors is demonstrated, the most potent is BB94, with an IC$\sb{50}$ value of only 0.8 nM. Thus, the role of matrilysin, the smallest enzyme in its family, in the involuting uterus is likely to be both activation of collagenase and general digestion of extracellular matrix components.

Keywords

Biology, Molecular; Chemistry, Biochemistry

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9519721