Increased expression of messenger RNA for collagen type I, collagen type III, and fibronectin in myometrium of pregnancy

Objective: To determine the expression of the extracellular matrix proteins collagen type I, collagen type III, and fibronectin by immunohistochemistry, and the messenger RNA (mRNA) for these proteins by Northern blot analysis in the myometrium of pregnancy compared with myometrium from normal premenopausal women. Methods: Myometrial tissue was obtained from seven pregnant women undergoing elective cesarean delivery and eight nonpregnant premenopansal women undergoing hysterectomy. Tissue was paraffin embedded and processed for RNA. Antibodies to collagen type I, collagen type III, and fibronectin were used to examine protein expression by immunohistochemistry. Complimentary DNA probes for the same proteins were used to examine mRNA expression by Northern blot analysis. Results: Increased staining was seen for all three proteins in the myometrium of pregnancy. Densitometric analysis of Northern blots showed increased levels of collagen type I mRNA (P < .003), collagen type III mRNA (P < .005), and fibronectin mRNA (P < .04) in the myometrium of pregnancy compared with myometrium from nonpregnant premenopausal women. Conclusion: There is increased expression of both protein and mRNA for collagen type I, collagen type III, and fibronectin in the myometrium of pregnancy.