Luteal and hypophyseal expression of the canine relaxin (RLN) system during pregnancy: Implications for luteotropic function.

By acting through its receptors (RXFP1, RXFP2), relaxin (RLN) exerts species-specific effects during pregnancy; possible luteotropic effects through stimulation of prolactin (PRL) release have been suggested. In the domestic dog (Canis lupus familiaris) serum PRL increases in pregnant bitches shortly after RLN appears in the circulation, and a possible functional relationship between the RLN and the PRL systems in regulating progesterone secretion has been implied. Therefore, here (Study 1) the luteal expression and localization of the RLN system was investigated by immunohistochemistry using custom-made antibodies and semi-quantitative PCR, at selected time points during gestation: pre-implantation (d. 8-12), post-implantation (d. 18-25), mid-gestation (d. 35-40) and at normal and antigestagen-induced luteolysis. Further, (Study 2) hypophyseal expression of the RLN system and its spatial association with PRL was assessed. Luteal expression of RLN, but not of its receptors, was time-dependent: it increased significantly following implantation towards mid-gestation and decreased at prepartum. Antigestagen treatment resulted in downregulation of RLN and RXFP2. Whereas RLN was localized in steroidogenic cells, RXFP1 and RXFP2 also stained strongly in macrophages and vascular endothelial cells. The RLN system was detected in the canine adenohypophysis and was co-localized with PRL in hypophyseal lactotrophs. The intraluteal RLN seems to be involved in regulating the canine corpus luteum (CL) in a time-dependent manner. The presence of RLN family members in the adenohypophysis implies their possible involvement in regulating the availability of PRL and other pituitary hormones.

Serelaxin for the treatment of heart failure.

Outcomes for patients with acute heart failure remain suboptimal and treatments principally target improvement of symptoms. To date there has been no therapy approved for acute heart failure shown to improve mortality or readmission risk post-discharge. Serelaxin, a recombinant form of the naturally occurring polypeptide hormone relaxin, has demonstrated promise in preclinical and early clinical trials as a potentially novel therapy for acute heart failure. It is postulated through its anti-fibrotic and vasodilatory effects that this agent can improve outcomes in both the short and long term in these patients. Randomized clinical data has suggested that the medication is safe and well tolerated. However, definitive outcomes data is currently being assessed in a large multi-center trial.

Relaxin deficiency results in increased expression of angiogenesis- and remodelling-related genes in the uterus of early pregnant mice but does not affect endometrial angiogenesis prior to implantation.

BACKGROUND: Extensive uterine adaptations, including angiogenesis, occur prior to implantation in early pregnancy and are potentially regulated by the peptide hormone relaxin. This was investigated in two studies. First, we took a microarray approach using human endometrial stromal (HES) cells treated with relaxin in vitro to screen for target genes. Then we aimed to investigate whether or not relaxin deficiency in mice affected uterine expression of representative genes associated with angiogenesis and uterine remodeling, and also blood vessel proliferation in the pre-implantation mouse endometrium. METHODS: Normal HES cells were isolated and treated with recombinant human relaxin (10 ng/ml) for 24 h before microarray analysis. Reverse transcriptase PCR was used to analyze gene expression of relaxin and its receptor (Rxfp1) in ovaries and uteri; quantitative PCR was used to analyze steroid receptor, angiogenesis and extracellular matrix remodeling genes in the uteri of wild type (Rln+/+) and Rln-/- mice on days 1-4 of pregnancy. Immunohistochemistry localized endometrial endothelial cell proliferation and mass spectrometry measured steroid hormones in the plasma. RESULTS: Microarray analysis identified 63 well-characterized genes that were differentially regulated in HES cells after relaxin treatment. Expression of some of these genes was increased in the uterus of Rln+/+ mice by day 4 of pregnancy. There was significantly higher vascular endothelial growth factor A (VegfA), estrogen receptor 1 (Esr1), progesterone receptor (Pgr), Rxfp1, egl-9 family hypoxia-inducible factor 1 (Egln1), hypoxia inducible factor 1 alpha (Hif1α), matrix metalloproteinase 14 (Mmp14) and ankryn repeat domain 37 (Ankrd37) in Rln-/- compared to Rln+/+ mice on day 1. Progesterone receptor expression and plasma progesterone levels were higher in Rln-/- mice compared to Rln+/+ mice. However, endometrial angiogenesis was not advanced as pre-implantation endothelial cell proliferation did not differ between genotypes. CONCLUSIONS: Relaxin treatment modulates expression of a variety of angiogenesis-related genes in HES cells. However, despite accelerated uterine gene expression of steroid receptor, progesterone and angiogenesis and extracellular matrix remodeling genes in Rln-/- mice, there was no impact on angiogenesis. We conclude that although relaxin deficiency results in phenotypic changes in the pre-implantation uterus, endogenous relaxin does not play a major role in pre-implantation angiogenesis in the mouse uterus.

Human recombinant H2 relaxin induces AKT and GSK3ß phosphorylation and HTR-8/SVneo cell proliferation.

Relaxin is essential for trophoblast development during pregnancy. Evidence shows that relaxin increases trophoblast cell migration capacity. Here, we show the effect of relaxin on protein kinase B (AKT) activation and glycogen synthase kinase 3-beta (GSK3ß) inactivation as well as on the proliferation of HTR-8/SVneo cells, a model of human extravillous trophoblast (EVT). HTR-8/SVneo cells were treated with different doses of human recombinant (rH2) relaxin in serum-deprived conditions and treated for increasing time with 1 ng/mL of rH2 relaxin. Western blot analysis was performed to detect pAKT, AKT, pGSK3ß, GSK3ß, and actin expression. Proliferation of HTR-8/SVneo cells was analyzed by MTS assay. rH2 relaxin treatment increased the ratio of pAKT/AKT, pGSK3ß/GSK3ß, and proliferation in HTR-8/SVneo cells. Furthermore, AKT and GSK3ß activation by rH2 relaxin was inhibited by a phosphoinositide 3-kinase (PI3K) inhibitor. This study suggests that rH2 relaxin induces AKT and GSK3ß phosphorylation as well as proliferation in HTR-8/SVneo cells.

Review of the Multiscale Effects of Female Sex Hormones on Matrix Metalloproteinase-Mediated Collagen Degradation.

Collagenases and gelatinases regulate many physiological processes and are involved in the pathogenesis and progression of various disease states, such as osteoarthritis, renal fibrosis, and atherosclerosis. These enzymes belong to the matrix metalloproteinase (MMP) family and are regulated by a number of factors, including sex hormones. Estrogen, relaxin, and progesterone can alter the balance between tissue degradation and repair by modulating MMPs, leading to gender disparities in many MMP-related disease states. In these diseases, MMPs initiate collagen degradation at the nanoscale when they cleave and denature collagen molecules. However, the net effect on tissue is generally observed at the macroscale. To understand how nanoscale events lead to macroscale changes, we must examine the intermediate scales. In this article, we review the literature that examines the effects of estrogen, relaxin, and progesterone on MMP production and activity, connecting the nanoscale, microscale, and macroscale details to relevant disease states.

RELAXIN enhances differentiation and matrix mineralization through Relaxin/insulin-like family peptide receptor 2 (Rxfp2) in MC3T3-E1 cells in vitro.

RELAXIN (RLN) is a polypeptide hormone of the insulin-like hormone family; it facilitates birth by softening and widening the pubic symphysis and cervix in many mammals, including humans. The role of RLN in bone metabolism was recently suggested by its ability to induce osteoclastogenesis and activate osteoclast function. RLN binds to RELAXIN/INSULIN-LIKE FAMILY PEPTIDE 1 (RXFP1) and 2 (RXFP2), with varying species-specific affinities. Young men with mutated RXFP2 are at high risk for osteoporosis, as RXFP2 influences osteoblast metabolism by binding to INSULIN-LIKE PEPTIDE 3 (INSL3). However, there have been no reports on RLN function in osteoblast differentiation and mineralization or on the functionally dominant receptors for RLN in osteoblasts. We previously described Rxfp1 and 2 expression patterns in developing mouse oral components, including the maxillary and mandibular bones, Meckel's cartilage, tongue, and tooth primordia. We hypothesized that Rln/Rxfp signaling is a key mediator of skeletal development and metabolism. Here, we present the gene expression patterns of Rxfp1 and 2 in developing mouse calvarial frontal bones as determined by in situ hybridization. In addition, RLN enhanced osteoblastic differentiation and caused abnormal mineralization and extracellular matrix metabolism through Rxfp2, which was predominant over Rxfp1 in MC3T3-E1 mouse calvarial osteoblasts. Our data suggest a novel role for Rln in craniofacial skeletal development and metabolism through Rxfp2.

Relaxin: new pathophysiological aspects and pharmacological perspectives for an old protein.

Human relaxin-2 (hereafter simply defined as "relaxin") is a 6-kDa peptidic hormone best known for the physiological role played during pregnancy in the growth and differentiation of the reproductive tract and in the renal and systemic hemodynamic changes. This factor can also be involved in the pathophysiology of arterial hypertension and heart failure, in the molecular pathways of fibrosis and cancer, and in angiogenesis and bone remodeling. It belongs to the relaxin peptide family, whose members comprehensively exert numerous effects through interaction with different types of receptors, classified as relaxin family peptide (RXFP) receptors (RXFP1, RXFP2, RXFP3, RXFP4). Research looks toward the in-depth examination and complete understanding of relaxin in its various pleiotropic actions. The intent is to evaluate the likelihood of employing this substance for therapeutic purposes, for instance in diseases where a deficit could be part of the underlying pathophysiological mechanisms, also avoiding any adverse effect. Relaxin is already being considered as a promising drug, especially in acute heart failure. A careful study of the different RXFPs and their receptors and the comprehension of all biological activities of these hormones will probably provide new drugs with a potential wide range of therapeutic applications in the near future.

Therapeutic effect of oncolytic adenovirus expressing relaxin in radioresistant oral squamous cell carcinoma.

Radioresistance is one of the main determinants of treatment outcome in oral squamous cell carcinoma (OSCC), and treatment of radioresistant OSCC is difficult due to cross resistance to other conventional treatments. We aimed to identify whether genetically modified oncolytic adenovirus expressing relaxin (RLX), which affects collagen metabolism, can effectively inhibit growth of the radioresistant OSCC. Therapeutic effect of oncolytic adenovirus was compared between radiosensitive and radioresistant OSCC cell lines in vitro and in vivo, and spread of adenovirus throughout the tumor mass was verified by immunohistochemistry (IHC). Oncolytic adenovirus effectively killed cancer cells and there was no significant difference in the cytotoxic effect between radiosensitive and radioresistant OSCC cell lines. In animal experiments, the adenovirus significantly reduced the size of tumor, and there was no significant difference between radiosensitive and radioresistant OSCC. In IHC, RLX expressing adenovirus showed better proliferation and eliminated collagens more effectively compared to RLX nonexpressing adenovirus. These findings suggested that genetically modified oncolytic adenovirus can effectively inhibit growth of the radioresistant OSCC and might be a new therapeutic option in radioresistant OSCC.

RNAi-mediated knockdown of relaxin decreases in vitro proliferation and invasiveness of osteosarcoma MG-63 cells by inhibition of MMP-9.

PURPOSE: The purpose of this study is to determine the role of relaxin knowdown by siRNA transfection in cellular growth and invasion of osteosarcoma MG-63 cells, and discusses the molecular mechanisms of this action. MATERIALS AND METHODS: The expression of relaxin in MG-63 cell was examined by western blot or RT-PCR. To evaluate the biological role of relaxin, proliferation assay (MTT) and invasion assay (BD Matrigel™), apoptosis assay (TUNEL and ELISA) and cell cycle analysis (flow cytometer) were performed after silencing relaxin using siRNA. MMP-9 expressions were analyzed using RT-PCR, western blot and zymography after silencing relaxin. RESULTS: Results showed that the downregulation of relaxin expression by siRNA in human osteosarcoma MG-63 cells significantly inhibited cell proliferation and invasion in vitro. Furthermore, relaxin knockdown led to cell arrest in the G1/G0 phase of the cell cycle, and eventual apoptosis enhancement in MG-63 cells. We provide evidence in our cell model that the relaxin siRNA down-regulated the expression of MMP-9 and the MMP-9 activity, suggesting that relaxin may promote the proliferation, invasion and metastasis of osteosarcoma cells by regulating the expression of MMP-9 and facilitating ECM degradation. CONCLUSIONS: Therefore, siRNA-directed knockdown of relaxin may represent a viable clinical therapy for osteosarcoma.

Central relaxin-3 receptor (RXFP3) activation decreases anxiety- and depressive-like behaviours in the rat.

Relaxin-3 is a recently discovered neuropeptide and the results of earlier anatomical and pharmacological studies suggest it plays a physiological role in modulating functions such as arousal, learning and memory, food intake and neuroendocrine homeostasis. Relaxin-3 is also postulated to modulate affective behaviour, based on high densities of the relaxin-3 G-protein coupled receptor (RXFP3) in brain areas involved in stress and mood/anxiety, including the central amygdala, bed nucleus of the stria terminalis and hypothalamic paraventricular nucleus (PVN); and strong activation of relaxin-3 neurons by stressors, via activation of corticotropin-releasing factor receptor-1 (CRF1). This study assessed the effect of central administration of a newly developed RXFP3-selective agonist, on anxiety- and depressive-like behaviour in rats. Adult, male Sprague-Dawley rats administered 5 µg [R3A(11-24,C15→A)B] (referred to as RXFP3-A2), intracerebroventricularly, demonstrated decreased anxiety-like behaviour in the light-dark box and elevated plus maze, but not in the open field. Notably, in the repeat forced swim test, central RXFP3-A2 administration decreased immobility in rats that had been subjected to the 'stress' of former exposure to the anxiety tests, but not in experimentally naïve rats. These data implicate relaxin-3/RXFP3 signalling in the modulation of effects of acute (anxiety) and cumulative (depression) neurogenic stressors on behaviour; and suggest a potential for RXFP3 agonists as anxiolytic and anti-depressant agents. In addition, our results demonstrate that exposure of adult Sprague-Dawley rats to tests of anxiety-like behaviour (∼10-14 days prior) can significantly increase immobility time in the repeat forced swim test.

Reproductive tract actions of relaxin in models of human pregnancy.

Elucidating the role(s) of relaxin in women has been greatly hampered by its species specificity. Suitable experimental models of relaxin action in women are limited. We established a non-human primate model of early human pregnancy to study the effects of relaxin in vivo and used three well characterized in vitro models of human endometrial function for study of mechanisms involved. Results from these studies clearly demonstrate that relaxin is an import ant factor in human endometrium which causes accommodation to and maintenance of early pregnancy and uses multiple physiological and biochemical mediators.

Human relaxin-2: historical perspectives and role in cancer biology.

One of the most recognised and studied family of peptide hormones is the insulin superfamily. Within this family is the relaxin subfamily which comprises seven members: relaxin-1, -2 and -3 and insulin-like peptides 3, 4, 5 and 6. Besides exhibiting sequence similarities, each member exists as an active A-B heterodimer linked by three disulfide bonds. This mini-review is divided into three broad themes: an overview of all insulin superfamily members (including structural similarities); roles of each superfamily member and finally, a focus on the pleiotropic peptide hormone, human relaxin-2. In addition to promoting vasodilatory effects leading to evaluation in Phase III clinical trials for the treatment of acute heart failure, relaxin has recently been shown to be highly expressed by cancer cells, aiding in their proliferation, invasiveness and metastasis. These contrary effects of relaxin are discussed together with current efforts in the development of relaxin antagonists that may possess future therapeutic potential for the treatment of certain cancers.

Relaxin induces matrix-metalloproteinases-9 and -13 via RXFP1: induction of MMP-9 involves the PI3K, ERK, Akt and PKC-ζ pathways.

We determined the precise role of relaxin family peptide (RXFP) receptors-1 and -2 in the regulation of MMP-9 and -13 by relaxin, and delineated the signaling cascade that contributes to relaxin's modulation of MMP-9 in fibrocartilaginous cells. Relaxin treatment of cells in which RXFP1 was silenced resulted in diminished induction of MMP-9 and -13 by relaxin, whereas overexpression of RXFP1 potentiated the relaxin-induced expression of these proteinases. Suppression or overexpression of RXFP2 resulted in no changes in the relaxin-induced MMP-9 and -13. Studies using chemical inhibitors and siRNAs to signaling molecules showed that PI3K, Akt, ERK and PKC-ζ and the transcription factors Elk-1, c-fos and, to a lesser extent, NF-κB are involved in relaxin's induction of MMP-9. Our findings provide the first characterization of signaling cascade involved in the regulation of any MMP by relaxin and offer mechanistic insights on how relaxin likely mediates extracellular matrix turnover.

Gene duplication and positive selection explains unusual physiological roles of the relaxin gene in the European rabbit.

The relaxin gene family is a group of genes involved in different physiological roles, most of them related to reproduction. In vertebrates the genes in this family are located in three separate chromosomal locations, and have been called relaxin family locus (RFL) A, B, and C. Among mammals the RFLA and RFLC are the most conserved as no gene copy-number variation has been observed thus far. The RFLB locus is also conserved on most mammals other than primates, where there are several gene gains and losses. Interestingly, the relaxin gene found on the RFLB locus in the European rabbit has acquired a novel role. In addition to the classical reproductive roles, this gene is expressed in tracheobronchial epithelial cells and its expression has been linked to squamous differentiation. We reconstructed the evolutionary history of the European rabbit RFLB locus using the tools of comparative genomics and molecular evolution. We found that the European rabbit possess a RFLB locus which is unique among mammals in that there are five tandemly arranged relaxin gene copies, which contrast with the single relaxin copy gene found in most mammals. In addition we also found that the ancestral pre-duplication gene was subject to the action of positive selection, and several amino acid sites were identified under the action of natural selection including the sites B12 and B13 which are part of the receptor recognition and binding site.

Effect of relaxin on human sperm functions.

Relaxin is a circulating hormone with functions in pregnancy, parturition, and other aspects of female reproduction. It is also secreted from the prostate gland into the seminal fluid; however, the role of relaxin in male reproduction is debated. Studies conducted in the past have suggested possible actions on human spermatozoa, but the data were contrasting. Here, we show that the relaxin receptor RXFP1 (Relaxin Family Peptide Receptor 1) is expressed in human spermatozoa, and it mainly localizes in the astrodome. In vitro studies on human sperm demonstrated that this hormone attenuates the natural decline in sperm motility and maintains higher mitochondrial activity and lower apoptosis level. Furthermore, relaxin induced an increase in sperm hyperactivation, intracellular calcium and cAMP, and acrosome reaction. These effects were abolished by the use of the specific anti-RXFP1 antibody. Relaxin concentrations were low in the blood (x ± SD, 0.16 ± 0.03 nM) and very high in the seminal plasma (x ± SD, 10.3 ± 4.0 nM), confirming its secretion mainly by the prostate. Taken together, these data demonstrate that relaxin influences positively many sperm functions linked to fertilizing ability, and it preserves sperm functionality, with possible practical value in assisted reproduction techniques.

Relaxin and castration in male mice protect from, but testosterone exacerbates, age-related cardiac and renal fibrosis, whereas estrogens are an independent determinant of organ size.

This study determined the effects of castration and hormone replacement therapy on the age-related cardiac and renal pathology of male relaxin gene-knockout (RlnKO) and age-matched wild-type (RlnWT) mice and that of aged male aromatase knockout (ArKO) mice, which lack estrogens and have 5-10 times the androgen levels of male wild-type mice. One-month-old RlnWT and RlnKO mice were bilaterally gonadectomized or sham operated and maintained until 12 months. Subgroups of castrated animals received testosterone or 17ß-estradiol treatment from 9 to 12 months. Male ArKO mice and aromatase wild-type mice were aged to 12 months. Collected heart and kidney tissues were assessed for changes in organ size and fibrosis. Castration reduced body, heart, left ventricle, and kidney weights in both RlnKO and RlnWT mice, and the cardiac/renal fibrosis that was seen in sham RlnKO animals (all P < 0.05 vs. respective sham). Testosterone normalized organ weights and organ weight to body weight ratio of castrated animals and increased cardiac/renal collagen concentration to levels measured in or beyond that of sham RlnKO mice (all P < 0.05 vs. respective castrated mice). Furthermore, expression of TGF-ß1, mothers against decapentaplegic homolog 2 (Smad2), and myofibroblast differentiation paralleled the above changes (all P < 0.05 vs. respective castrated mice), whereas matrix metalloproteinase-13 was decreased in testosterone-treated RlnKO mice. Conversely, 17ß-estradiol only restored changes in organ size. Consistent with these findings, intact ArKO mice demonstrated increased cardiac/renal fibrosis in the absence of changes in organ size. These findings suggest that relaxin and castration protect, whereas androgens exacerbate, cardiac and renal fibrosis during ageing, whereas estrogens, in synergy with relaxin, regulates age-related changes in organ size.

Lactocrine programming of female reproductive tract development: environmental connections to the reproductive continuum.

For eutherian mammals a continuum of maternal support insures that development of progeny follows an optimal program. Beginning in utero, such support extends into the early neonatal period when bioactive factors are communicated from mother to offspring in colostrum/milk. Defined as lactocrine signaling, communication of milk-borne bioactive factors from mother to offspring as a consequence of nursing is important for development of somatic tissues, including the female reproductive tract (FRT). Data for the domestic pig indicate that lactocrine signaling contributes to the maternal continuum of factors that define the developmental program and determine the developmental trajectory of FRT tissues during early neonatal life. Both naturally occurring and manmade factors of environmental origin can be communicated to neonates in milk and affect development with lasting consequences. Here, evidence for lactocrine programming of FRT development and the potential for environmental endocrine disruption of this process are reviewed.

Relaxin induces rapid dilation of rodent small renal and human subcutaneous arteries via PI3 kinase and nitric oxide.

The peptide hormone relaxin is a potent vasodilator with therapeutic potential in diseases complicated by vasoconstriction, including heart failure. However, the molecular mediators and magnitude of vasodilation may vary according to duration of exposure and artery type. The objective of these studies was to determine mechanisms of rapid (within minutes) relaxin-induced vasodilation and to examine whether relaxin dilates arteries from different animal species and vascular beds. Rat and mouse small renal, rat mesenteric, and human sc arteries were isolated, mounted in a pressure arteriograph, and treated with recombinant human relaxin (rhRLX; 1-100 ng/ml) after preconstriction with phenylephrine. Rat and mouse small renal as well as human sc arteries dilated in response to rhRLX, whereas rat mesenteric arteries did not. Endothelial removal or pretreatment with l-N(G)-monomethyl arginine (L-NMMA) abolished rapid relaxin-induced vasodilation; phosphatidylinositol-3-kinase (PI3K) inhibitors also prevented it. In cultured human endothelial cells, rhRLX stimulated nitric oxide (assessed using 4-amino-5-methylamino-2'7'-difluorofluorescein) as well as Akt and endothelial NO synthase (eNOS) phosphorylation by Western blotting but not increases in intracellular calcium (evaluated by fura-2). NO production was attenuated by inhibition of Gα(i/o) and Akt (using pertussis toxin and the allosteric inhibitor MK-2206, respectively), PI3K, and NOS. Finally, the dilatory effect of rhRLX in rat small renal arteries was unexpectedly potentiated, rather than inhibited, by pretreatment with the vascular endothelial growth factor receptor inhibitor SU5416. We conclude that relaxin rapidly dilates select arteries across a range of species. The mechanism appears to involve endothelial Gα(i/o) protein coupling to PI3K, Akt, and eNOS but not vascular endothelial growth factor receptor transactivation or increased calcium.

Characterization and biological activity of relaxin in porcine milk.

A lactocrine mechanism for delivery of maternally derived relaxin (RLX) into the neonatal circulation as a consequence of nursing was proposed for the pig. Immunoreactive RLX was detected in colostrum and in the serum of newborn pigs only if they were allowed to nurse. Milk-borne RLX concentrations are highest during early lactation (9-19  ng/ml), declining to <2  ng/ml by postnatal day 14. Whether milk-borne RLX is bioactive is unknown. Evidence that RLX concentrations in milk are higher than in maternal circulation in several species suggests the mammary gland as a site of local RLX production. It is unknown whether the porcine mammary gland is a source of RLX. Therefore, objectives were to evaluate RLX bioactivity in porcine milk during the first 2 weeks of lactation, identify the form of RLX in porcine milk, and determine whether mammary tissue from early lactation is a source of milk-borne RLX. Milk RLX bioactivity was determined using an in vitro bioassay in which cAMP production by human embryonic kidney (HEK293T) cells transfected with the human RLX receptor (RXFP1) was measured. RLX bioactivity was highest at lactation day (LD) 0, decreasing to undetectable levels by LD 4. Immunoblot analysis of milk proteins revealed an 18  kDa band, indicating proRLX as the primary form of RLX in porcine milk. ProRLX protein and transcripts were detected in porcine mammary tissue on LD 0 and 7. Results support the lactocrine hypothesis by defining the nature and a potential source for bioactive proRLX in porcine colostrum/milk.

Endometrial expression of relaxin and relaxin receptor in endometriosis.

Our studies demonstrate significantly lower expression of relaxin and its receptor in ectopic endometriotic tissues than their expression in eutopic endometrium and in endometrium from normal controls. These data suggest that in normal and eutopic endometrium, relaxin may exert a protective effect against endometriosis.