Transforming growth factor 1 (TGF1) is a multifunctional cytokine which acts to regulate proteins of the extracellular matrix. It has been shown to increase the production of collagen and proteoglycans. Because both substances are thought to play a role in cervical remodeling, we hypothesized that TGF1 and its receptors would increase in early gestation before decreasing at term. This study therefore aims to determine the expression of TGF1 and its receptors in the cervix during pregnancy.
The cervix of non pregnant and timed pregnant rats at days 12, 16, 18, 20, 21 and 22 of gestation were obtained and analyzed for mRNA expression of TGF1, TGF-Receptor 1 (TR1), TR2, and TR3 using a 5′endonuclease assay. Multiplex assays were performed in triplicate using -actin as an internal control. Four animals were sacrificed for each time point using an IACUC approved protocol. Western blotting was used to determine protein concentration. Blots were normalized using -actin. SMAD phosphorylation was assessed to confirm activation of TGF1 signaling pathway. Data was analyzed using ANOVA.
TGF1 mRNA increased through day 21 before declining on day 22 of gestation (ANOVA p=0.001). The mRNA expression of TR1 and TR2 did not change with advancing gestation. TR3 m-RNA expression followed a similar pattern as TGF1 and increased through day 18 before a sharp decline was seen on day 22 of gestation (ANOVA p=0.001). Western blot analysis of TR3 protein expression followed a similar pattern to the mRNA expression (ANOVA p=0.017). Increased SMAD phosphorylation paralleled changes in TR3.
TR3 is known to increase TR1 activation by facilitating TR2-ligand interactions. Collagen type 1, the main stress bearing structural protein, also increases through pregnancy. It is possible that changes within the cervical extracellular matrix are regulated by signaling between TGF1 and TR3.
Supported by NIH-NCRR P20 RR018728
© 2008 Mosby, Inc. Published by Elsevier Inc. All rights reserved.