Expression of parathyroid hormone-related protein and its receptor in human umbilical cord: evidence for a paracrine system involving umbilical vessels

The Role of PTHLH in Ovarian Follicle Selection, Its Transcriptional Regulation and Genetic Effects on Egg Laying Traits in Hens

In hens, follicle selection is an important process affecting egg laying traits. This study investigated the role of parathyroid hormone-like hormone (PTHLH) in chicken follicle selection, its transcriptional regulation and genetic effects on egg laying traits. PTHLH and its receptor PTH1R were mainly expressed in follicles of 6–8 mm in diameter, exhibits differential expression pattern in the theca and granulosa cells of pre- and hierarchal follicles. PTHLH stimulates the proliferation of follicular granulosa and theca cells, the expression of StAR and CYP11A1 mRNA and the production of progesterone (P4) in pre-hierarchal follicles. Treatment with FSH increased PTHLH mRNA expression in pre-hierarchal follicular theca cells and hierarchal follicular granulosa cells. Two critical regions regulating chicken PTHLH transcription were revealed, each of which harbored a SNP: C>T (chr1: 72530014) for AP-1 and a SNP: A>G (chr1: 72531676). Hens with diplotype AC/GT were younger at first laying and laid more eggs at 32 weeks. The haplotype (G^-1827T^-165) with double mutations had the greatest promoter activity of chicken PTHLH transcription. Collectively, PTHLH plays an important role in chicken follicle selection by stimulating cell proliferation and steroidogenesis. Polymorphisms in chicken PTHLH promoter region are associated with egg laying traits by affecting the binding of transcription factor AP-1.

Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery

During pregnancy and lactation, female physiology adapts to meet the added nutritional demands of fetuses and neonates. An average full-term fetus contains ∼30 g calcium, 20 g phosphorus, and 0.8 g magnesium. About 80% of mineral is accreted during the third trimester; calcium transfers at 300-350 mg/day during the final 6 wk. The neonate requires 200 mg calcium daily from milk during the first 6 mo, and 120 mg calcium from milk during the second 6 mo (additional calcium comes from solid foods). Calcium transfers can be more than double and triple these values, respectively, in women who nurse twins and triplets. About 25% of dietary calcium is normally absorbed in healthy adults. Average maternal calcium intakes in American and Canadian women are insufficient to meet the fetal and neonatal calcium requirements if normal efficiency of intestinal calcium absorption is relied upon. However, several adaptations are invoked to meet the fetal and neonatal demands for mineral without requiring increased intakes by the mother. During pregnancy the efficiency of intestinal calcium absorption doubles, whereas during lactation the maternal skeleton is resorbed to provide calcium for milk. This review addresses our current knowledge regarding maternal adaptations in mineral and skeletal homeostasis that occur during pregnancy, lactation, and post-weaning recovery. Also considered are the impacts that these adaptations have on biochemical and hormonal parameters of mineral homeostasis, the consequences for long-term skeletal health, and the presentation and management of disorders of mineral and bone metabolism.

Bone development and mineral homeostasis in the fetus and neonate: roles of the calciotropic and phosphotropic hormones

Mineral and bone metabolism are regulated differently in utero compared with the adult. The fetal kidneys, intestines, and skeleton are not dominant sources of mineral supply for the fetus. Instead, the placenta meets the fetal need for mineral by actively transporting calcium, phosphorus, and magnesium from the maternal circulation. These minerals are maintained in the fetal circulation at higher concentrations than in the mother and normal adult, and such high levels appear necessary for the developing skeleton to accrete a normal amount of mineral by term. Parathyroid hormone (PTH) and calcitriol circulate at low concentrations in the fetal circulation. Fetal bone development and the regulation of serum minerals are critically dependent on PTH and PTH-related protein, but not vitamin D/calcitriol, fibroblast growth factor-23, calcitonin, or the sex steroids. After birth, the serum calcium falls and phosphorus rises before gradually reaching adult values over the subsequent 24-48 h. The intestines are the main source of mineral for the neonate, while the kidneys reabsorb mineral, and bone turnover contributes mineral to the circulation. This switch in the regulation of mineral homeostasis is triggered by loss of the placenta and a postnatal fall in serum calcium, and is followed in sequence by a rise in PTH and then an increase in calcitriol. Intestinal calcium absorption is initially a passive process facilitated by lactose, but later becomes active and calcitriol-dependent. However, calcitriol's role can be bypassed by increasing the calcium content of the diet, or by parenteral administration of calcium.

Calcium Homeostasis in Human Placenta: Role of Calcium‐Handling Proteins

The human placenta is a transitory organ, representing during pregnancy the unique connection between the mother and her fetus. The syncytiotrophoblast represents the specialized unit in the placenta that is directly involved in fetal nutrition, mainly involving essential nutrients, such as lipids, amino acids, and calcium. This ion is of particular interest since it is actively transported by the placenta throughout pregnancy and is associated with many roles during intrauterine life. At term, the human fetus has accumulated about 25-30 g of calcium. This transfer allows adequate fetal growth and development, since calcium is vital for fetal skeleton mineralization and many cellular functions, such as signal transduction, neurotransmitter release, and cellular growth. Thus, there are many proteins involved in calcium homeostasis in the human placenta.

Women with palmoplantar pustulosis have disturbed calcium homeostasis and a high prevalence of diabetes mellitus and psychiatric disorders: a case-control study

Palmoplantar pustulosis is characterized by pustule formation in the acrosyringium. Nearly 50% of palmoplantar pustulosis sera produce immunofluorescence of the palmar papillary endothelium from healthy subjects, but also of the endothelium of normal parathyroid gland. With a case-control design the levels of calcium and parathyroid hormone in serum were measured in 60 women with palmoplantar pustulosis and 154 randomly selected population-based control women. One-third of the controls had been smokers, whereas 95% of the cases were or had been smokers. Mean age-adjusted serum calcium was increased in the patients compared with the controls (2.43 vs 2.36 mmol/l; p<0.0001), whereas the parathyroid hormone concentration was suppressed (23.2 vs 31.1 ng/l; p<0.0001). The plasma levels of parathyroid hormone-related protein were normal in patients but there was a strong expression of this protein in the acrosyringium both in palmoplantar pustulosis and control skin. As even a marginal elevation of serum calcium is associated with an increased risk for diabetes, cardiovascular disease and psychiatric disease, we analysed the risk for these disorders in palmoplantar pustulosis patients compared with that in the control group. Both diabetes mellitus and psychiatric disorders were associated with palmoplantar pustulosis with an odds ratio of 8.7 (95% CI 3.3-22.8) and 5.6 (95% CI 2.2-14.4), respectively. Palmoplantar pustulosis is a complex disease with an increased risk for several non-dermatological disorders. The role of the mildly increased serum calcium for the high risk for diabetes and depression deserves to be studied.

PTH/PTHrP Receptor and Mid-molecule PTHrP Regulation of Intrauterine PTHrP: PTH/PTHrP Receptor Antagonism Increases SHR Fetal Weight

Parathyroid hormone-related protein (PTHrP) has important roles in fetal growth and development through stimulation of placental calcium transport, vasodilatation of the uteroplacental vasculature and regulation of cellular growth and differentiation. The growth restricted spontaneously hypertensive rat (SHR) has reduced fetal plasma, placental and amniotic fluid PTHrP concentrations compared to its progenitor, the Wistar Kyoto (WKY) rat. The aim of this study was to determine whether intrauterine PTHrP infusions can restore PTHrP levels and promote SHR fetal growth. PTHrP(1-34), midmolecule PTHrP(67-94), the PTH/PTHrP receptor antagonist [Asn(10), Leu(11)]-PTHrP(7-34) or vehicle were infused via a mini-osmotic pump between 10 and 20 days of gestation into the uterine lumen of SHR and WKY rats. Uterine, placental, amniotic fluid and plasma (fetal and maternal) PTHrP were measured via N-terminal radioimmunoassay. PTH/PTHrP receptor antagonism and mid-molecule PTHrP(67-94) induced endogenous intrauterine PTHrP production with receptor antagonism eliciting a greater and more wide spread effect. The PTH/PTHrP receptor antagonist [Asn(10), Leu(11)]-PTHrP(7-34) acting through a receptor other than the PTH/PTHrP receptor increased SHR fetal and placental weights above vehicle (P<0.05) to that of the WKY and restored SHR amniotic fluid volume (P<0.05). This was associated with a highly significant up regulation of placental, uterine and plasma (fetal and maternal) PTHrP (P<0.05). Modest increases in placental and uterine PTHrP (P<0.05) following intrauterine infusions of PTHrP(1-34) and PTHrP(67-94) had no effect on WKY and SHR fetal weight. Effective growth promoting actions of increased endogenous PTHrP were observed following PTH/PTHrP receptor antagonism rather than exogenous PTHrP administration. A novel finding was that mid-molecule PTHrP also up regulates endogenous intrauterine N-terminal PTHrP production supporting the existence of a mid-molecule receptor. This study highlights that an increase in endogenous uterine, placental and fetal plasma PTHrP following PTH/PTHrP receptor antagonism was associated with increased SHR fetal growth presumably by improving placental growth and function.

Bone in the pregnant mother and newborn at birth

BACKGROUND

Changes in maternal bone during pregnancy may affect fetal bone mineralization.

ISSUES

The biphasic changes in maternal bone histology (temporary loss of cancellous bone in early pregnancy restored by term gestation) are consistent with corresponding blood biochemistry changes; increased bone resorption markers in the first trimester, while bone formation markers increased in the last trimester. Postpartum bone mineral density (BMD) by DEXA is increased at cortical bone and decreased at trabecular bone sites compared with prepregnancy values. The mean reduction of spine BMD is 3.5% from prepregnancy to immediate postpartum. Neonatal bone mineral content (BMC) is different by season of birth, low weight relative to gestation, and having a diabetic mother. Lower total body BMC and high bone resorption marker in winter vs. summer-born newborns was related to low vitamin D, indicating alterations of fetal bone metabolism by maternal D deficiency. Lower BMC and decreased bone formation marker in infants born small for gestational age than those born appropriate for gestation may relate to reduced transplacental mineral transfer. Low BMC in infants of diabetic mother was correlated inversely with poor control of maternal diabetes during early pregnancy.

CONCLUSIONS

During pregnancy, maternal bone mineral metabolism are changed, and influences on fetal bone mineralization occur in utero.

Expression of PTHrP and its cognate receptor in the rheumatoid synovial microcirculation

Parathyroid hormone-related protein (PTHrP), a multifunctional peptide that acts as a vasodilator as well as possible regulator of vascular development, is produced in increased amounts in the rheumatoid synovium. To understand whether PTHrP can contribute to the development and function of the rheumatoid microcirculation, studies were undertaken to identify and compare vascular sites of expression of PTHrP and its cognate receptor in the rheumatoid synovium and/or in cultured rheumatoid synovial endothelial cells. Endothelial cells, including apoptotic cells, as determined by TUNEL staining, were the primary site of vascular PTHrP expression in the rheumatoid synovium, a result confirmed in vitro in rheumatoid synovial microvascular endothelial cells. In contrast, the PTH/PTHrP receptor was primarily located in pericytes and smooth muscle cells within the vasculature. These results are consistent with a possible paracrine pathway for PTHrP action in the synovial microcirculation, wherein PTHrP peptides secreted by the synovial endothelium could act on surrounding PTH1R-positive pericytes and smooth muscle cells.

Regulation of secretion of PTHrP by Ca(2+)-sensing receptor in human astrocytes, astrocytomas, and meningiomas

Parathyroid hormone-related protein (PTHrP) is the major mediator of the humoral hypercalcemia of malignancy and of malignant osteolysis associated with skeletal metastases of common epithelial cancers. PTHrP secretion is regulated by the extracellular calcium concentration ([Ca(2+)](o)) in several types of normal and malignant cells. Because the [Ca(2+)](o)-sensing receptor (CaR) is a key mediator of [Ca(2+)](o)-regulated hormone secretion [e.g., of parathyroid hormone (PTH) by parathyroid chief cells], we investigated the expression of the CaR and PTHrP in normal and neoplastic glial cells and studied the effects of [Ca(2+)](o) on PTHrP secretion. Our results show that primary embryonic human astrocytes (HPA) express CaR mRNA and protein as detected by RT-PCR and Western analysis, respectively. Furthermore, astrocytomas and meningiomas also express the CaR at similar levels as assessed by RT-PCR and Northern and Western blot analyses. HPA and astrocytomas express transcripts encoding all three known isoforms of PTHrP [PTHrP(139), PTHrP(141), and PTHrP(173), comprising 139, 141, and 173 predicted amino acid residues, respectively] as assessed by RT-PCR, whereas meningiomas express only the first two of these. Finally, elevated levels of [Ca(2+)](o) and other polycationic CaR agonists dose dependently stimulate PTHrP secretion from HPA, astrocytomas, and meningiomas, although both basal and high [Ca(2+)](o)-stimulated rates of PTHrP secretion are approximately 2. 5-fold higher in HPA than in the glial tumors studied here. Therefore, our results show that HPA, astrocytomas, and meningiomas express both the CaR and PTHrP and that CaR agonists stimulate PTHrP secretion.

Intrauterine expression of parathyroid hormone-related protein in normal and pre-eclamptic pregnancies

Maternal hypertension, vasoconstriction and placental insufficiency are features of pre-eclampsia. Alterations in calcium homeostasis and in the production of calciotropic hormones and vasoactive agents have also been described in association with pre-eclampsia. Parathyroid hormone-related protein (PTHrP) is abundantly expressed in intrauterine tissues during normal pregnancy and has roles in fetal growth and calcium homeostasis, placental calcium transport and vascular tone regulation. Intrauterine PTHrP mRNA expression and tissue PTHrP content were determined by Northern blot analysis and radio-immunoassay, respectively, in preterm and term pre-eclamptic women. PTHrP mRNA expression and PTHrP content in placenta, amnion over placenta, reflected amnion and choriodecidua from preterm pre-eclamptic women (n=8-10) were not different from preterm controls (n= 10-12). PTHrP mRNA expression and content in amnion over placenta and reflected amnion were significantly greater in term compared to preterm pre-eclamptics (P<0.05). PTHrP mRNA expression was significantly lower in choriodecidua from term pre-eclamptic women (n=8) compared to term controls (n=28, P<0.05), but was not different in placenta or amnion. PTHrP content was not altered in term pre-eclamptic women (n=8) compared to controls (n=25) for any tissue. In summary, PTHrP expression in placenta and amnion was not increased in pre-eclamptic women in association with maternal hypertension, placental insufficiency and vasoconstriction. PTHrP mRNA expression was decreased in choriodecidua in association with term but not preterm pre-eclampsia, however, levels of the protein were not decreased. The data suggest that PTHrP is not involved in the placental pathophysiology of pre-eclampsia in late gestation.

Mechanical stretch increases secretion of parathyroid hormone-related protein by cultured bladder smooth muscle cells

Parathyroid hormone-related protein (PTHrP) immunoreactivity has been detected in the bladder and increases in response to dilatation secondary to obstruction. The hypothesis that PTHrP could be increased solely by stretch rather than other possible in vivo variables was tested by stretching cultured bladder smooth muscle cells and analyzing the culture medium for this protein. In response to mechanical stretch, PTHrP was increased in smooth muscle cell cultures. Immunoradiometric assay revealed maximal rates of secretion for the first eight hours. Comparison of percent change in PTHrP secretion of flexed cells for the various flex parameters revealed a difference (p = .006) when the degree of stretch (i.e. percent elongation) was altered. The protein synthesis inhibitor cycloheximide inhibited basal and stretch-induced PTHrP secretion. PTHrP (1-100 nM) relaxed carbachol-contracted bladder body and base by 15% and 45% respectively. PTHrP did not affect bladder contractions induced by potassium (124 mM) or alpha-beta MeATP (10 microM). Increased PTHrP secretion in response to stretch of smooth muscle raises the possibility of an autocrine action to relax the bladder during filling. PTHrP may also exert a paracrine action on vessels regulating blood flow during bladder filling or it may modulate neural activity.

Expression and specific immunolocalization of the human parathyroid hormone/parathyroid hormone-related protein receptor in the uteroplacental unit

OBJECTIVE

Our purpose in these studies was to determine the expression and cellular localization of the parathyroid hormone/parathyroid hormone-related protein receptor in the human uteroplacental unit.

STUDY DESIGN

Human uteroplacental tissues were obtained and ribonucleic acid was extracted. Reverse transcriptase-polymerase chain reaction was performed with use of primers for both the parathyroid hormone/parathyroid hormone-related protein receptor and human phosphoglyceraldehyde dehydrogenase. Ethidium bromide-stained gels and Southern blots were evaluated, and polymerase chain reaction fragments were sequenced. For immunohistochemistry, slides were incubated with a newly developed antibody (3D1.1) specific for the parathyroid hormone/parathyroid hormone-related protein receptor, and bound monoclonal antibody was detected by use of the avidin-biotin technique.

RESULTS

Reverse transcriptase polymerase chain reaction gels and blots showed that receptor messenger ribonucleic acid was present in choriodecidua, placenta, and myometrium. Sequence analysis revealed complete identity of the receptor product and the known nucleotide sequence in the receptor. There was intense receptor staining of the myometrial smooth muscle as well as staining of the endothelium and smooth muscle of the associated vasculature. In umbilical cord immunoreactive receptor was found in the vascular endothelium and vascular smooth muscle cells and in stromal cells. In choriodecidua receptor was found in chorionic trophoblasts and decidualized endometrial stromal cells. In all tissues immunostaining was specific, as evidenced by the blocking of staining after addition of receptor peptide to the antibody (absorbed controls).

CONCLUSION

The parathyroid hormone/parathyroid hormone-related protein receptor is widely expressed in the human uteroplacental unit. The cellular localizations of the receptor in smooth muscle reflect the ability of parathyroid hormone-related protein to relax both uterine and vascular smooth muscle. The presence of novel autocrine and paracrine systems in the human uteroplacental unit is suggested by the finding that the same cells or adjacent cells produce both parathyroid hormone-related protein and its receptor.

Vascular effects of PTHrP (1-34) and PTH (1-34) in the human fetal-placental circulation

The aim of this study was to examine the vasodilatory effects of parathyroid hormone-related protein (PTHrP) (1-34) and parathyroid hormone (PTH) (1-34) on the human fetal-placental circulation utilising an in vitro placental perfusion model. In all experiments, the vasculature of an isolated human placental cotyledon was pre-constricted with the thromboxane A2 mimetic U46619. A simple dose of PTHrP (1-34) or PTH (1-34) (1.7-300 nM) was then infused into the fetal-placental circulation of the cotyledon. In other experiments, cotyledons were repeatedly infused with PTHrP (1-34) or PTH (1-34) (51.3 nM). Vasodilatory responses were significantly reduced in response to repeated exposure to PTHrP (1-34) (P < 0.001), indicating that this peptide desensitizes the fetal-placental vasculature. PTHrP (1-34) and PTH (1-34) equipotently stimulated a significant vasodilation of the fetal-placental circulation (P < 0.0001). The PTHrP receptor antagonist [Asn10, Leu 11]PTHrP (7-34) (102 nM) was infused in U46619-constricted placentae in the presence and absence of PTHrP (1-34) (10.2 nM). The PTHrP antagonist alone had no significant effect in the fetal-placental circulation. The antagonist significantly attenuated the response to PTHrP (1-34) (P < 0.015). Based on the data obtained in this study it is suggested that locally produced PTHrP (1-34) may be involved in the regulation of normal human fetal-placental vascular tone in autocrine and/or paracrine fashion.

Parathyroid hormone-related peptide (PTHrP) regulates fetal-placental calcium transport through a receptor distinct from the PTH/PTHrP receptor

To determine the role of PTHrP in fetal calcium metabolism, blood calcium was measured in mice homozygous (HOM) for deletion of the PTHrP gene. On day 18.5 of gestation, ionized calcium and the maternal-fetal calcium gradient were significantly reduced in HOM PTHrP-ablated fetuses compared with that of their littermates. To assess the placental contribution to the effect of PTHrP, 45Ca and 51Cr-EDTA (as a blood diffusional marker) were administered by intracardiac injection to pregnant, heterozygous dams on day 17.5 of gestation. Five minutes after the injection, whole fetal 45Ca accumulation was significantly decreased in HOM PTHrP-ablated fetuses compared with that of their littermates. Next, two fetuses from each litter were injected in utero with fragments of PTHrP, PTH, or diluent 1 h before administering 45Ca and 51Cr to the dam. PTHrP-(1-86) and PTHrP-(67-86) significantly increased relative 45Ca accumulation in HOM PTHrP-ablated fetuses, but PTHrP-(1-34), PTH-(1-84), and the diluent had no effect. Finally, similar studies were performed on fetal mice that lacked the PTH/PTHrP receptor gene. Ionized calcium was significantly reduced in HOM PTH/PTHrP receptor-ablated fetuses. However, 5 min after maternal injection of 45Ca and 51Cr, relative accumulation of 45Ca was significantly increased in these fetuses. It was concluded that PTHrP is an important regulator of fetal blood calcium and placental calcium transport. In addition, the bioactivity of PTHrP for placental calcium transport is specified by a mid-molecular region that does not use the PTH/PTHrP receptor.

Distribution and functions of parathyroid hormone-related protein in vertebrate cells

Parathyroid hormone-related protein (PTHrP) was isolated from tumors and identified as the agent of humoral hypercalcemia of malignancy (HHM) in 1987. Since then its gene structure in several mammalian and an avian species has been analyzed and its gene expression demonstrated in many adult and embryonic tissues derived from all three germ layers. The composition and structure of PTHrP peptide depends on both differential gene splicing and posttranslational processing, which result in a range of peptides of potentially diverse functions. This chapter describes the distribution of PTHrP in both normal and neoplastic adult and embryonic tissues. PTHrP is of fundamental importance to cell survival because the absence of the gene is fatal; this aspect of PTHrP function in cell physiology becomes overwhelmingly important in neoplasia. Intracrine or paracrine actions for PTHrP seem to be most likely in mammalian and avian physiology, but in fishes high circulating levels suggest classic endocrine functions as well. Much remains to be learned of the biology of this fascinating protein.

Immunoreactive parathyroid hormone-related protein: its association with preterm labor

OBJECTIVE

Parathyroid hormone-related protein (PTHrP) is a 141 amino acid protein which contains a 1-36 N-terminal domain resembling parathyroid hormone which has smooth muscle relaxant activity and a mid (67-86) domain which reportedly alters placental calcium transport. Using specific antibodies to these regions of PTHrP, the objective of this study was to determine changes in the levels and localization of the peptides in placenta and membranes that might be indicative of their biological activity and role during term and preterm labor.

STUDY DESIGN

Placenta and fetal membranes were collected from patients with preterm delivery (PTL) (n = 16), term cesarean section in the absence of labor (n = 10) and term vaginal delivery (n = 5). Immunohistochemistry was performed with specific antisera visualized by the avidin-biotin peroxidase method and the staining intensity was quantified with an image analysis system MCID.

RESULTS

Immunoreactive (ir)-PTHrP(1-34) and ir-PTHrP(67-86) were localized to the amnionic epithelium chorionic trophoblasts, decidual cells and placental syncytiotrophoblast. Intense immunostaining was observed for ir-PTHrP(67-86) but not for ir-PTHrP(1-34) in the endothelial lining of the villous capillaries. Ir-PTHrP(1-34) staining was lower in placenta and fetal membranes of PTL patients compared with term cesarean section in the absence of labor (P < 0.05 Mann-Whitney test). In contrast, there was no difference in ir-PTHrP [67-86] staining intensity between delivery categories.

CONCLUSION

These results showing differential localization of PTHrP(1-34) and PTHrP(67-86) suggest cell specific processing of PTHrP precursor in the human placenta. Moreover, the changes in ir-PTHrP(1-34) but not ir-PTHr(67-86) with labor are indicative of a particular role for this peptide in the delivery process.

Expression of parathyroid hormone-related peptide and its receptor messenger ribonucleic acid in human amnion and chorion-decidua: implications for secretion and function

OBJECTIVE

Our purpose was to define the location and packaging of parathyroid hormone-related peptide in amnion-chorion and the potential target tissues for its action in fetal membranes.

STUDY DESIGN

We studied fetal membranes by use of light microscopic immunocytochemistry with three monoclonal antibodies against distinct regions of the parathyroid hormone-related peptide molecule. For electron microscopy immunogold analysis with a monoclonal antibody specific to the 109-141 fragment was used to observe parathyroid hormone-related peptide intracellularly in amnion membrane and in the chorion layers. Multiplex reverse transcriptase-polymerase chain reaction with Southern blotting was used to identify parathyroid hormone/parathyroid hormone-related peptide receptor and control messenger ribonucleic acids in amnion and chorion-decidua.

RESULTS

All monoclonal antibodies revealed immunoreactive parathyroid hormone-related peptide in the amniotic epithelial cells and in some fibroblast-like cells embedded in the extracellular matrix of the amnion. Parathyroid hormone-related peptide was also found in the chorion in fibroblast and trophoblast layers and in decidua. Ultrastructurally immunogold particles were evenly distributed throughout the amniotic epithelial cells and were present in apical microvilli and near the basal membranes. Electron microscopy studies of the chorion cytotrophoblast also showed freely dispersed immunogold particles of parathyroid hormone-related peptide with no packaging in secretory granules. Low to undetectable levels of parathyroid hormone/parathyroid hormone-related peptide receptor messenger ribonucleic acid were found in amnion tissue, whereas abundant receptor messenger ribonucleic acid was found in chorion-decidua.

CONCLUSIONS

These results suggest the presence of a parathyroid hormone-related peptide paracrine system within the human fetal membranes.

Interleukin-1 beta and interleukin-4 increase parathyroid hormone-related protein secretion by human umbilical vein endothelial cells in culture

OBJECTIVE

Our purpose was to learn whether cytokines such as interleukin-1 beta and related (or antagonistic) cytokines, hormones, and growth factors could regulate secretion of the vasorelaxant parathyroid hormone-related protein in human umbilical vein endothelial cells in culture.

STUDY DESIGN

Secondary cultures of human umbilical vein endothelial cells were grown to confluence and treated with interleukin-1 beta, an array of factors with possible regulatory actions (cytokines, growth factors, vasoactive peptides, and steroids), and a phorbol ester as a stimulatory control. After 24 hours immunoreactive parathyroid hormone-related peptide in the media was measured by a two-site sandwich radioimmunoassay. The mechanism of interleukin-1 beta action was probed with interleukin-1 beta receptor antagonist and selected inhibitors.

RESULTS

Interleukin-1 beta (10 ng/ml) produced up to an eightfold increase in parathyroid hormone-related peptide secretion from human umbilical vein endothelial cells in culture (p < 0.01). Half-maximal stimulation was seen at 0.23 ng/ml. Interleukin-1 receptor antagonist, cycloheximide, and actinomycin D blocked the effects of interleukin-1 beta (p < 0.05). Interleukin-4 at 10 ng/ml and phorbol 12-myristate 13-acetate at 10(-7) mol/L significantly increased the secretion of parathyroid hormone-related peptide by human umbilical vein endothelial cells (p < 0.05). The time course of each interleukin showed an effect beyond 12 hours. The effects of interleukin-1 beta and interleukin-4 appeared to be specific, because a large series of related interleukins and other growth factors and cytokines were without effect.

CONCLUSION

Interleukin-1 beta and interleukin-4 increase parathyroid hormone-related protein secretion in human umbilical vein endothelial cells in culture. Because interleukin-1 beta messenger ribonucleic acid has been found in umbilical cord endothelial cells, we propose that the umbilical cord has a novel vasorelaxant regulatory system that uses interleukin-1 beta endothelial action and secretion of the vasorelaxant parathyroid hormone-related peptide.