Changes in glycosaminoglycan composition of normal human placentas with maturation

Placental syndecan expression is altered in human idiopathic fetal growth restriction

Pregnancy represents a hypercoagulable state characterized by increased thrombin generation. However, placentas from fetal growth restriction (FGR) pregnancies are characterized by increased fibrin deposition and thrombi in the vasculature, indicative of a further increase in thrombin activation and a disturbance in coagulation in this clinical setting. The cause of the coagulation disturbance observed in FGR pregnancies is currently unknown. Anticoagulant mechanisms are crucial in the regulation of thrombin activity, and current evidence suggests that syndecans are the principal placental anticoagulant proteoglycans. The aim of this study was to determine the localization, distribution, and expression of syndecans 1 to 4 in placentas complicated by idiopathic FGR compared with gestation-matched controls. Immunohistochemistry results revealed that all of the syndecans were localized to cells located closely to the maternal and fetal circulation. The mRNA and protein expression levels of both syndecan 1 and syndecan 2 were significantly decreased in FGR samples compared with controls. This is the first study to demonstrate the differential expression of syndecans 1 to 4 in idiopathic FGR placentas compared with controls. Reduced levels of syndecan expression may result in increased placental thrombosis in the uteroplacental circulation and may therefore contribute to the pathogenesis of FGR.

Decorin expression is decreased in human idiopathic fetal growth restriction

Fetal growth restriction (FGR) is a clinically significant pregnancy disorder in which the fetus fails to achieve its full growth potential in utero. Most cases of FGR are idiopathic and are associated with placental thrombosis. Previous studies suggest that proteoglycans, such as decorin, that contain the glycosaminoglycan dermatan sulfate are the principal anticoagulants in the normal placenta. The present study investigated decorin expression in placentas from pregnancies complicated by idiopathic FGR (n = 26) and gestation-matched controls (n = 27). Real-time polymerase chain reaction demonstrated significantly reduced decorin mRNA expression in FGR compared with control (1.52 ± 0.14 v. 2.21 ± 0.22, respectively; P < 0.01). Immunoblotting revealed decreased decorin protein (40 kDa) expression in FGR compared with controls (420.8 ± 39.0 v. 690.1 ± 42.2, respectively; n = 12 in each group; P = 0.0007). Immunohistochemistry demonstrated the presence of immunoreactive decorin protein in the placental villous stroma surrounding the fetal capillaries and a significant decrease in decorin protein presence in FGR compared with control (1.75 ± 0.66 v. 2.98 ± 1.12, respectively; n = 6 in each group; P < 0.01, t-test). This is the first study to demonstrate reduced decorin in idiopathic FGR, indicating a potentially significant role for decorin in the aetiology of placental thrombosis in idiopathic FGR.

Chondroitin sulfate in normal human plasma is modified depending on the age. Its evaluation in patients with pseudoxanthoma elasticum

Plasma chondroitin sulfate (CS) amount and charge density were determined in 45 healthy volunteers (control group), 45 pseudoxanthoma elasticum (PXE)-affected patients and 19 healthy carriers by using fluorophore-assisted carbohydrate electrophoresis (FACE) and HPLC equipped with postcolumn derivatization and fluorescence detection. The mean values of CS amount were 4.9+/-1.21 for volunteers, 4.7+/-1.40 for PXE subjects and 4.4+/-1.44 for the carriers. No significant differences were found for the three human subjects groups. On the contrary, by considering the age of normal volunteers, a significant increase of plasma CS amount was measured. In fact, the volunteers aging from 17 to 40 years (mean 32.1) showed a CS concentration of 4.3+/-1.30 while the group ranging from 50 to 74 years (mean 56.9) had a value of 5.6+/-1.16 with a significant increase of +30.2%. The same significant increase in CS plasma content with increasing age was measured for PXE-affected and healthy carriers group. Extracted plasma CS was evaluated for the main two unsaturated disaccharides, non-sulfated and 4-monosulfated, and the charge density determined. The mean values were 0.54+/-0.13 for volunteers, 0.60+/-0.15 for PXE subjects and 0.50+/-0.15 for the carriers. A significant increase of +11.1% was found between the PXE patients and healthy human group but no differences were calculated between the control group and the carriers. Furthermore, besides a CS amount, the volunteers aging from 17 to 40 years (mean 32.1) showed a charge density of 0.53+/-0.14 while the group ranging from 50 to 74 years (mean 56.9) had a value of 0.58+/-0.17 with a significant increase of +9.4%. The same trend was measured for the healthy carriers group. The CS charge density of PXE-affected subjects was found to increase significantly more than healthy controls depending on the age. In fact, the PXE patients aging from 10 to 40 years (mean 29.3) showed a charge density of 0.56+/-0.14 while the group ranging from 50 to 74 years (mean 58.6) had a value of 0.67+/-0.11 with a significant increase of +19.6%. Furthermore, the group of PXE-affected subjects ranging from 50 to 74 years (mean 58.6) showed a significant increase of 15.5% in comparison with the group matched for age (mean 56.9) of healthy volunteers.

Enzymatic synthesis of chondroitin with a novel chondroitin sulfate N-acetylgalactosaminyltransferase that transfers N-acetylgalactosamine to glucuronic acid in initiation and elongation of chondroitin sulfate synthesis

We found a novel glycosyltransferase gene having a hypothetical beta 1,4-galactosyltransferase motif (GenBank accession number ) by a BLAST search and cloned its full-length open reading frame using the 5'-rapid amplification of cDNA ends method. The truncated form was expressed in insect cells as a soluble enzyme. It transferred N-acetylgalactosamine, not galactose, to para-nitrophenyl-beta-glucuronic acid. The N-acetylgalactosamine-glucuronic acid linkage has been identified only in chondroitin sulfate; therefore, we examined its chondroitin elongation and initiation activities. N-Acetylgalactosaminyltransferase activity was observed toward chondroitin poly- and oligosaccharides, chondroitin sulfate oligosaccharides, and linkage tetrasaccharide (GlcA-Gal-Gal-Xyl-O-methoxyphenyl), and the chondroitin polysaccharide and linkage tetrasaccharide were better acceptor substrates than the others. Northern blot analysis and quantitative real-time PCR analysis revealed that its 4-kb transcripts were highly expressed in thyroid and placenta, although they were ubiquitously expressed in various tissues and cells. These results suggest that this enzyme has N-acetylgalactosaminyltransferase activity in both the elongation and initiation of chondroitin sulfate synthesis. Furthermore, we performed enzymatic synthesis of chondroitin pentasaccharide in vitro. In one tube reaction with four enzymes, beta 1,4-galactosyltransferase-VII, beta 1,3-galactosyltransferase-VI, glucuronyltransferase-I, and this enzyme, and a synthetic xylose-peptide acceptor, the structure GalNAc-GlcA-Gal-Gal-Xyl-peptide was constructed. This is the first report of a chondroitin pentasaccharide constructed with recombinant glycosyltransferases in vitro.

Anticoagulant dermatan sulfate proteoglycan (decorin) in the term human placenta

Normal pregnancy is characterized by increased in vivo thrombin generation. A greater proportion of endogenously generated thrombin is complexed to heparin cofactor II in plasma from pregnant women compared to plasma from nonpregnant ones. The increase in thrombin-heparin cofactor II complexes suggests that the site of the additional thrombin generation is relatively rich in dermatan sulfate. We postulated that the site of thrombin generation may be the placenta since endogenous thrombin generation returns rapidly to normal after delivery. This report describes the isolation and characterization of placental dermatan sulfate proteoglycan from villous tissue of the term human placenta. Placental dermatan sulfate was isolated by guanidine HCI extraction and anion exchange chromatography. The isolated material was found to have anticoagulant activity with a relative activity of approximately 40% of that of a porcine mucosal dermatan sulfate which is undergoing clinical trial as an antithrombotic agent. The dermatan sulfate was present as a proteoglycan with a molecular mass of 90-150 kD. Upon degradation with chondroitin ABC lyase, the core protein was demonstrated to be a doublet with molecular masses of 42 and 44 kD. This core protein reacted with antiserum against the core protein of decorin on Western analysis. The role of this placental dermatan sulfate in local regulation of thrombin in the placenta warrants further study.

CD44 in human placenta: localization and binding to hyaluronic acid

CD44, a receptor for hyaluronic acid (HA), has been identified in the stroma of stem and terminal chorionic villi of human term placenta. The CD44 glycoprotein antigen, isolated from placenta by affinity to monoclonal antibody (mAb) 50B4, consisted mainly of species of M(r) 85,000 and 200,000. Radiolabelled CD44 bound specifically to HA attached to plastic, predominantly via the M(r) 85,000 species; this binding was inhibited by soluble HA and hyaluronidase. The binding of CD44 to HA was also inhibited by mAb 50B4 and IM7.8.1, which recognize epitopes of cluster I and II respectively, but was not blocked by a polyclonal antibody to peptide 18-30 of the B loop (residues 12-101). These results suggest that the portion of the B loop of CD44 implicated in the binding to HA is between amino acids 31-101 and that epitopes located outside the B loop, such as that recognized by mAb IM7.8.1 (between residues 132-215), contribute to this interaction. The presence of a functional CD44 molecule in the human term placenta suggest a role for this molecule in situ in the stabilization and orientation of HA network important in the maintenance of the structural integrity of the placenta.

High viscosity of newborn extracellular matrix is the etiology of erythema toxicum neonatorum: neonatal jaundice?: hyaline membrane disease?

At the time of birth, the fetal ground substance is under the influence of maternal and placental hormones. Hormones are known to exert significant effect on ground substance. The ground substance viscosity that is ideal for intrauterine life is too viscous for the newborn. Sites of minor skin trauma develop swelling, inflammation and pustules. Dilution of tissue fluids causes formation of some of the mediators of inflammation including those responsible for intraepidermal pustule formation. The newborn responds to inflammation with eosinophilic granulocyte. The clinical lesions referred to as erythema toxicum neonatorum are known to localize at pressure sites. The skin lesions correct as maternal and placental hormone influence weakens. The entity occurs in 31 to 72% of white infants. The hormone induced viscosity changes may aid in better understanding some aspects of neonatal physiology; such as jaundice of the neonatal period, the eosinophilic granulocyte inflammatory response of the neonatal period and hyaline membrane disease.

Relaxant effects of hexosamines on isolated small human placental arteries

Wharton's jelly contains large amounts of hyaluronic acid, and glucosamine is an important constituent of this macromolecule. In order to evaluate the placental vascular effects of this aminosugar, small chorionic and stem villous arteries were dissected from placental specimens obtained at normal term vaginal deliveries (n = 15). Ring preparations were mounted in organ baths, and isometric wall tensions were measured. Glucosamine and its epimer galactosamine (5 X 10(-4) to 10(-2) M) produced marked relaxation of contractions induced by PGF2 alpha (10(-5) M) in both chorionic and stem villous arteries. The effect was unchanged after pretreatment with atropin, propranolol and indomethacin. The relaxant effect of the neutral sugar mannose was less pronounced compared with that of the hexosamines. Total tissue concentrations of placental hexosamines have been reported within the range needed to produce placental vascular relaxation in the present study. However, the major part of these compounds is integrated in macromolecules, and the tissue level of free hexosamine is probably far below the total concentrations. Accordingly, the effects of hexosamines demonstrated in the present study might not be of physiological importance in the regulation of fetal placental medial smooth muscle tension.

Distribution and characterization of anionic sites in trophoblast and capillary basal laminas of human placental villi

The distribution of anionic sites was studied in the trophoblastic and fetal capillary basal laminas of developing human placental villi with the cationic stain ruthenium red. At 7-12 weeks of gestation the trophoblastic basal lamina (TBL) contained ruthenium red-positive granules in a quasi-regular array throughout the lamina densa or sometimes concentrated at the interstitial surface of the lamina densa. The capillary basal lamina (CBL) (and anionic sites) were not present at this age. Anionic sites were also associated with collagen or reticular fibrils. At term, the TBL was largely devoid of anionic sites except for some distributed along its interstitial surface. The CBL was present in later gestation and sometimes had arrays of anionic sites. In order to characterize the anionic sites, minced pieces of villi were incubated in the presence or absence of either chondroitinase ABC, heparitinase, neuraminidase, or Streptomyces hyaluronidase in appropriate buffer systems. Incubation of early villi with heparitinase resulted in the disappearance of the TBL-associated sites. Chondroitinase ABC appeared to reduce staining of collagen-associated sites. In term villi, heparitinase removed those few sites still associated with the TBL but did not affect sites associated with the CBL or collagen. Chondroitinase ABC resulted in the disappearance of all anionic sites. In later gestation, a number of developmentally important macromolecules are transported across the trophoblast and enter the fetal capillaries. We conclude that the absence of an array of polyanionic sites from the term placenta TBL and the reduction in the amount of extracellular matrix intervening between the trophoblast and capillaries are adaptations to enhance the exchange of macromolecules across the placenta.

Ultrastructural localization of glycosaminoglycans in human term placenta

Sulfated glycoconjugates were stained in normal human term placentas using Spicer's high-iron diamine (HID) method with thiocarbohydrazide and silver proteinate (TCH-SP) enhancement. Specific identification of glycosaminoglycans (GAG) was accomplished by digestion of the stained material with chondroitinase ABC or AC for removal of chondroitin sulfates and nitrous acid for removal of N-sulfated GAGs. The syncytiotrophoblast apical surface demonstrated moderate to intense staining with HID-TCH-SP, which was removed by prior digestion with the chondroitinases, but not by nitrous acid. The syncytiotrophoblast basal surface and endothelial cell surfaces lacked sulfate staining. A few cytoplasmic granules in syncytiotrophoblast cells demonstrated staining similar to the apical surface. Three layers of the basal lamina were identified in these preparations. The lamina lucida immediately beneath the syncytiotrophoblast and the majority of the lamina densa stained weakly or not at all, whereas the underlying lamina diffusa and stroma demonstrated moderate to intense staining. The majority of lamina diffusa staining was removed by chondroitinase ABC or AC; the remaining material was removed by nitrous acid digestion. Thus the syncytiotrophoblast surface contains a chondroitin sulfate and the basal lamina contains a mixture of intensely stained chondroitin sulfate and a weakly stained N-sulfated GAG.

Histochemical localization of acidic glycosaminoglycans in normal human placentae

First-trimester and term placentae were studied histochemically with alcian blue stain before and after specific enzyme treatments. A specific deposition of glycosaminoglycans was detected in the villous stroma, fetal blood vessels and on the surface of the syncytiotrophoblast, the latter being discontinuous and of variable thickness. Treatments of sections with hyaluronidases from Streptomyces and from bovine testes and with chondroitinase ABC indicated the presence of (1) chondroitin sulphates and hyaluronic acid mainly in the stroma; (2) heparan sulphate and dermatan sulphate associated with villous fetal blood vessels and the intervillous surface of the syncytiotrophoblast. It is suggested that the location of individual glycosaminoglycans could be related to their functions with regard to the maintenance of the structural integrity of the placenta by preventing its compression and to their involvement in blood anticoagulation and in lipid metabolism.

Histochemical and quantitative biochemical changes in mucopolysaccharides of the term placenta of the diabetic rat

Full-term placentae of rats with streptozotocin-induced diabetes were analysed histochemically and biochemically for changes in mucopolysaccharide content. The experimental diabetes induced severe cystic degeneration in the spongiosa zone of the placenta and this was accompanied by extracellular deposition of hyaluronate and neutral polysaccharides. The labyrinth zone was affected to a lesser extent. Biochemical analysis also revealed quantitative differences in the total contents of mucopolysaccharides (MPS) between the two zones of the placenta in both diabetic and normal placentae. The spongiosa had a higher total mucopolysaccharide content than the labyrinth. Polysaccharides of low molecular weight were always predominant. The amount of hyaluronate exceeded the quantitites of sulphated mucopolysaccharides which were found in relatively small amounts in both placental zones. In diabetic placentae there was a two- to threefold increase, which was more pronounced in the spongiosa. The increase was observed among all types of MPS. A close correlation between the accumulation of MPS in the placenta and the degree of maternal hyperglycaemia was found. The placentae of the three streptozotocin-resistant animals showed neither histological nor biochemical changes. It is suggested that the accumulation of MPS in the diabetic placenta might be a consequence of a shift in carbohydrate metabolism induced by hyperglycaemia or a persistence of the fetal metabolic features as a part of a retarded maturational process of the placenta.

Glycosaminoglycan patterns in diabetic and toxemic term placentas

Crude glycosaminoglycans were prepared from acetone powder of diabetic, toxemic, and normal term placentas. Glycosaminoglycan composition was determined by electrophoresis and densitometric scanning with and without treatment with testicular hyaluronidase and chondroitinase ABC. The identity of individual glycosaminoglycans was confirmed by the nature of their hexosamine. Glycosaminoglycan content was found to be significantly increased in diabetic placentas and increased to a lesser degree in the toxemic placentas. The amount of hyaluronic acid was elevated in both abnormal tissues, and heparan sulfate was slightly higher in diabetes, while unchanged in toxemia. Dermatan sulfate was markedly reduced in the abnormal placentas while chondroitin 4/6 sulfate was unaltered. An attempt was made to correlate the histopathologic changes reported to occur in these conditions with the alterations in the glycosaminoglycans patterns of placentas.