Changes in the Composition and Structure of Glycosaminoglycans in the Human Placenta during Development

Abstract

ExtractGlycosaminoglycans (acid mucopolysaccharides) are ubiquitous in their distribution in the body, yet information as to their biologic function is scanty. Studies of their structure and physical properties in solution suggest that they could function as gel nitration and exchange resins in vivo, thereby playing an important role in regulation of the passage of molecules through the ground substance of connective tissue. The glycosaminoglycan(s) (GAG) composition of the human placenta and the molecular structure of specific GAG has been studied by chemical, enzymatic, and physical methods at 12-18 weeks and at 40 weeks gestational age to explore this postulated structure-function relation.The young placenta contained more GAG (222 mg/100 mg dry defatted tissue) than did the term placenta (155 mg/100 g dry defatted tissue). Sulfated GAG comprised 56% of the total GAG in the young placenta versus 74% in the term placenta due to increased concentrations of dermatan sulfate (25% term versus 13% young placenta) and heparan sulfate (22% term versus 15% young placenta). Ghondroitin was a major component in the young placenta and comprised 22% of the total GAG, whereas the term placenta contained only 9%. Both young and term placenta showed similar quantities of hyaluronic acid and chondroitin 4-and 6-sulfates. Ghondroitin sulfate from the young placenta differed from the polymer in the term placenta in that it contained a higher proportion oi unsulfated dissaccharides. Differences were also found in the molecular structure of dermatan sulfate. Hyaluronidase digestion of purified dermatan sulfate from young placenta produced a 50% reduction in average molecular weight compared with a 30% reduction in the molecular weight of dermatan sulfate isolated from term placenta. The smaller molecular weight fragments of dermatan sulfate from young placenta indicate differences in molecular structure due either to the number of glucuronic acid substitutions or to their position in the polymer chain, or to changes in the concentration of hybrid molecules. Speculation

Chondroitin Sulfate Proteoglycan Expression and Binding ofPlasmodium falciparum-Infected Erythrocytes in the Human Placenta during Pregnancy

“…The observed increase in the levels of sulfation in CSPGs with increasing gestational age agrees with the results of a previous study (23). From determination of the sulfate contents of the total CS and CS-dermatan sulfate copolymeric chains from pooled placentas of 16 to 24 weeks and full term, it was reported that the sulfate content of the glycosaminoglycans increases with increasing gestational age (23). However, in that study, different classes of CSPGs in the placentas, their structural characteristics, and levels of expression during the course of pregnancy were not studied.…”

Composition and significance of glycosaminoglycans in the uterus and placenta of mammals

“…The literature reports on amorphous material, a dense electron that easily stains by Schiff Periodic Acid (SPA), in the placenta´s maternal-fetal interface which varies throughout pregnancy and also among mammal species (Lovell et al 1967;Calatroni and Di Ferrante 1969;Lee et al 1973;Wasserman et al 1983;Ott et al 1997). It may be surmised that changes in the placenta tissue during the maturation process, mainly in the molecular composition and structure of GAGs in the tissue may give rise to an extracellular matrix with different physical characteristics.…”

“…It may be surmised that changes in the placenta tissue during the maturation process, mainly in the molecular composition and structure of GAGs in the tissue may give rise to an extracellular matrix with different physical characteristics. Changes may alter molecule transport through the placenta´s connective tissue and would affect directly the rate of fetal growth (Lee et al 1973), which varies at different pregnancy phases. The placenta contains two important types of PGs, or rather, PGs with the HS chain and PGs with CS and DS.…”

“…GAGs undergo a change in their conformation and thus facilitate the inhibition of thrombin and avert the formation of thrombus in the placenta (Giri and Tollefsen 2006). It seems that GAGs and in particular CS and HA in ruminants may be involved in the formation of placentomes, a structure which is characteristic to the placenta, whose number is limited by the amount of fetal caruncles (Lee et al 1973;Greiss and Wagner 1983). At the onset of pregnancy, HA is the predominant GAG of the extracellular matrix of the placentomes, which seems to be restricted almost exclusively to the fetal villous mesenchyme.…”

“…Changes at GAGs levels with the maturation of the placenta would be related to the role of these molecules in the regulation of placenta transport. Lee et al (1973) Human -Placenta during the first 3 months -Placenta at term -Main GAGs: CS and HA in the placenta stroma and DS and HS associated with fetal blood vessels and syncytial surface.…”