Characterization of decorin mRNA in pregnant intrauterine tissues of the ewe and regulation by steroids

In this study, we characterized the changes in the extracellular matrix pro teoglycan decorin in pregnant intrauterine tissues in late gestation and in association with labor and delivery in sheep. In addition, we examined the effects of estradiol and progesterone on regulation of decorin mRNA expres sion in myometrium from the nonpregnant ovariectomized sheep. Using suppres sion subtractive hybridization in combination with Northern blot analysis, we identified a significant increase in decorin mRNA in the pregnant sheep myometrium during labor. The abundance of decorin mRNA paralleled myometria l contractility. The increase in decorin mRNA during labor was only demonst rated in the myometrium; no increase was observed in the endometrium or fet al membranes. Estradiol upregulated decorin mRNA and may act as a potential stimulator responsible for the increased decorin in the myometrium during parturition. The ovine decorin cDNA spans 1288 nt, includes 1083 nt of codi ng sequence predicted to encode a protein of 360 amino acids, 119 nt of 5'- untranslated region (UTR) and 86 nt of 3'-UTR. Over the coding region, the protein shares 79-96% nt sequence identity and 73-94% identity in the deduc ed amino acid sequence with homologous mammalian sequences. Using cloned de corin cDNA, we observed that the fibroblasts are the predominant cell type in the pregnant sheep myometrium containing decorin mRNA. These data sugges t that increased decorin synthesis participates in the matrix changes that may play a role in myometrial activation.