Progress 09/01/99 to 08/31/04
Outputs
Studies in rats and neonatal gilts indicate that uterotrophic actions of relaxin are estrogen receptor (ER)-dependent. Previous work on this grant has shown that at postnatal day (PND) 0, prior to the appearance of the ER, two-day relaxin treatment failed to increase uterine weight in neonatal gilts while significantly increasing cervical growth. Pretreatment with the antiestrogen, ICI 182, 780 did not block the relaxin-stimulated increase in cervical wet weight. Data indicate that trophic effects of relaxin are tissue-specific and involve ER-dependent (uterus) and ER-independent (cervix) pathways. The mechanism of this tissue-specific response to relaxin in the neonatal reproductive tract is unknown. The final studies supported by this grant conducted during the current period were to investigate relaxin receptor (LGR7) expression in the neonatal uterus and cervix and its regulation by relaxin. At PND 0, gilts were given porcine relaxin (30 ug, i.m.) or saline every 6
h for 48 h and sacrificed 3h after the last injection. Uterine and cervical RNA were isolated and subjected to quantitative RT-PCR using pig-specific primers. At PND 2, LGR7 expression in the cervix was higher than in the uterus (P< 0.001). In gilts treated with relaxin, uterine LGR7 levels did not change compared to controls. Interestingly, relaxin administration decreased cervical LGR7 expression (P< 0.001), when compared to controls. To our knowledge, this is the first time that relaxin is reported to regulate LGR7 expression in vivo. These data suggest that differential expression of LGR7 may contribute to tissue-specific relaxin responsiveness in the neonatal reproductive tract.
Impacts
Since relaxin is important in promoting reproductive tissue growth, a better understanding of how relaxin cross talks with estrogen receptor pathways and acts to regulate expression of its own receptor will help us to better understand how relaxin promotes uterine and cervical growth.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
The overall aim of these studies is to learn how the hormone relaxin (Rlx) promotes growth to facilitate uterine accommodation at the cellular level. Studies this year focused on the role of ligand-independent activation of the estrogen receptor by Rlx in promoting uterine and cervical growth in vivo. Studies in neonatal gilts shows that at birth (post natal day PND 0), prior to uterine estrogen receptor expression, there was no effect of Rlx or estradiol (E2) on uterine weight (Rlx: 123 + 7, E2: 122 + 5; Control 125 + 6 mg/kg BW). In contrast, Rlx increased cervical weight (554 + 66 mg/kg BW) when compared with E2-treated (294 + 24 mg/kg BW) or control gilts (298 +16 mg/kg BW; p <0.05). Later in neonatal life, on PND 14 when the estrogen receptor is present, there was a significant uterotrophic response to both E2 and Rlx (p<0.05). However, in the presence of the estrogen receptor antagonist, ICI 182, 780, the uterotrophic effects of both E2 and Rlx were
significantly inhibited (p<0.05). Data in the PND 0 gilt rule out estrogen contamination of the Rlx preparation as a factor in the observed uterotrophic effects since, unlike Rlx, E2 did not increase cervical weight in these animals. These studies demonstrate the value of the neonatal gilt in studying Rlx/ER interactions in the uterus and support the hypothesis that Rlx-induced uterine growth involves cross talk with the estrogen receptor.
Impacts
Since estrogens are important in promoting reproductive tissue growth, a better understanding of how relaxin cross talks with estrogen receptor pathways will help us to better understand how relaxin promotes uterine and cervical growth.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
The overall aim of these studies is to learn how the hormone relaxin promotes growth to facilitate uterine accommodation at the cellular level. Studies published this year focused on the impact of relaxin on uterine and cervical remodeling and expression of the tissue inhibitors of matrix metalloproteinases (TIMPs). In these studies prepubertal gilts were treated with relaxin to induce uterine and cervical growth and 54 h later tissues were collected. Relaxin significantly (p<0.05) increased TIMP-1 and TIMP-2 protein in uterine flushes and tissues. In the uterine cervix, relaxin enhanced expression of TIMP-1 and TIMP-2 (p<0.05), whereas expression of both TIMP proteins was similar in the vaginal cervix of control and relaxin-treated animals. Likewise, inhibitor activity was increased in response to relaxin administration in the uterine cervix and attenuated in extracts from the vaginal cervix. These data support a role for relaxin in regulating the activity of TIMPs
during growth and remodeling of reproductive connective tissue.
Impacts
Growth of reproductive tissue is the net result of mitogenic activity, as well as changes in tissue remodeling, which permit tissue expansion. Given the importance of uterine growth and remodeling during implantation and pregnancy, further studies on the control of uterine and cervical remodeling are important for a better understanding of reproductive function.
Publications
- Lenhart JA, Ryan PL, Ohleth KM, Palmer SS, Bagnell CA. 2002. Relaxin increases secretion of tissue inhibitor of matrix metalloproteinase-1 and -2 during uterine and cervical growth and remodeling in the pig. Endocrinology 143:91-98.
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Progress 01/01/01 to 12/31/01
Outputs
The overall aim of these studies is to learn how the hormone relaxin promotes growth to facilitate uterine accommodation at the cellular level. Studies this year focused on the impact of relaxin on uterine and cervical cell-cell adhesion by studying the cell adhesion molecule, epithelial (E)-cadherin. In these studies prepubertal gilts were treated with relaxin to induce uterine and cervical growth and 54 h later tissues were collected. E-cadherin mRNA and protein were measured by northern and western blot analysis, respectively. Relaxin significantly (p<0.05) increased E-cadherin protein and mRNA in the uterus, but not the cervix. E-cadherin was localized by immunohistochemistry to the epithelial cells of the uterine and cervical lumen and the uterine glandular epithelium. Administration of relaxin to prepubertal gilts increased uterine epithelial cell growth independent of circulating steroids, with a concomitant increase in E-cadherin expression.
Impacts
Growth of reproductive tissue is the net result of mitogenic activity, as well as changes in cell-cell adhesion, which permit tissue expansion. This is the first study to describe E-cadherin expression in the pig reproductive tract and localize E-cadherin to specific cells in the uterus and cervix during relaxin-induced growth. Given the importance of uterine growth and remodeling during implantation and pregnancy, further studies on the control of cell adhesion are important for a better understanding of uterine growth and function.
Publications
- Ryan PL, Baum DL, Lenhart JA, Ohleth KM, Bagnell CA. 2001. Uterine and cervical epithelial cadherin expression during relaxin-induced growth. Reproduction 122:929-937.
- Lenhart JA, Ryan PL, Ohleth KM, Palmer SS, Bagnell CA. 2001. Relaxin increases secretion of matrix metalloproteinase-2 and -9 during uterine and cervical growth and remodeling in the pig. Endocrinology 142:3941-3949.
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Progress 01/01/99 to 12/31/99
Outputs
The aim of these studies is to learn how relaxin promotes growth to facilitate uterine accommodation at the cellular level. One possibility is that relaxin enhances local angiogenesis which would increase the delivery of nutrients and growth factors to tissues adjacent to expanding uterine capillary beds. Vascular endothelial growth factor (VEGF) is a secreted, endothelial cell-specific growth factor which stimulates formtion of new blood vessels. Therefore, in the past 3 months since this project was funded we have focused on the question: Does relaxin stimulate VEGF protein expression in the porcine uterus? Using a prepubertal pig model, in which relaxin administration in vivo promotes uterine growth, we have evidence that VEGF protein expression is significantly higher than in control animals. In addition, we have localized porcine VEGF protein by immunohistochemistry in endometrial glands and in the periphery of blood vessels. The intensity of VEGF immunostaining
was higher in the uterine glands and blood vessels of relaxin-treated animals. Thus, these studies support the hypothesis that the uterotropic actions of relaxin involve stimulation of new blood vessel growth. Studies are continuing to uncover the role of relaxin in promoting uterine growth and angiogenesis.
Impacts
This is the first evidence that relaxin stimulates production of VEGF in the porcine uterus. These data suggest that relaxin promotes uterine growth by stimulating local angiogenesis.
Publications
- No publications reported this period
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