Thrombospondin-1 expression in human myometrium before and during pregnancy, before and during labor, and in human myometrial cells in culture.
The activation of latent transforming growth factor beta (L-TGFbeta) is essential for the action of TGFbeta, which, in turn, is involved in the regulation of expression of some progesterone-responsive genes. One mechanism by which TGFbeta is activated involves thrombospondin (TSP), a protein that binds extracellular proteins. Immunoreactive TSP (irTSP) protein and TSP-1 mRNA in myometrial tissues of ovulatory and pregnant women were localized by immunohistochemistry and in situ hybridization. IrTSP and TSP-1 mRNA were randomly distributed in myometrial smooth muscle cells of some, but not all, tissues of pregnant women at term before labor; but in some areas of most of these tissues, irTSP was intense and commonly localized extracellularly. Intense irTSP and TSP-1 mRNA in myocytes were more common in myometrium during labor. In myometrium from ovulatory women (n = 26), irTSP was localized primarily in vascular smooth muscle cells and was detected occasionally in scattered myocytes. Little TSP-1 mRNA was demonstrable by in situ hybridization in vessels or myocytes of myometrial tissue from ovulatory women (n = 7). By Northern analysis of total RNA, TSP-1 mRNA was detected in myometrial tissue of pregnant women and in human myometrial smooth muscle cells in culture. The levels of TSP-1 mRNA in myometrial tissues of pregnant women during labor (n = 18) were greater than those in myometrium at > 37 wk gestation before labor began (n = 25, p < 0.001). The ratios of TSP-1 to glyceraldehyde 3-phosphate dehydrogenase mRNAs in 3 myometrial tissues during oxytocin-induced labor were not statistically different from those in myometrium during spontaneous labor but were greater than those in myometrium before labor (p < 0.05). The level of TSP-1 mRNA in confluent human myometrial cells in culture was relatively high, was increased by treatment with fetal bovine serum, and was decreased by treatment with platelet-derived growth factor or activators of adenylyl cyclase or protein kinase C. Myometrial cells in culture constitute a useful model for studying the regulation of TSP-1 gene expression in human myometrium.
Morimoto
T
T
The Cecil H. and Ida Green Center for Reproductive Biology Sciences and the Departments of Obstetrics-Gynecology, Biochemistry, and Cell Biology-Neuroscience, The University of Texas Southwestern Medical School, Dallas, Texas 75235-9051, USA.
Head
J R
JR
MacDonald
P C
PC
Casey
M L
ML
D000328:Adult; D015152:Blotting, Northern; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007743:Labor, Obstetric / Q000378:metabolism*; D009215:Myometrium / Q000166:cytology / Q000378:metabolism*; D011247:Pregnancy / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D019700:Thrombospondin 1 / Q000096:biosynthesis*
D012333:RNA, Messenger; D019700:Thrombospondin 1