Ultrastructure of first trimester chorionic villi with regard to the prenatal diagnosis of genodermatoses

Abstract

Hopes are held out for chorion villus sampling, a technique which is gaining more and more importance for the first trimester prenatal diagnosis of chromosomal aberrations and metabolic abnormalities. A variety of inherited skin diseases can be diagnosed postnatally and prenatally (in the second trimester) by ultrastructural diagnostic markers. For evaluation of prenatal diagnosis in the first trimester, we investigated chorionic villi derived from the trophoblast layer of the early pregnancy by light microscopy and conventional electron microscopy. The ultrastructure of the cellular layers covering the villi, i.e., the inner cytotrophoblast and the outer syncytiotrophoblast, as well as that of the connective tissue of the inner extraembryonic mesoderm, are thoroughly described in relation to the ultrastructural changes in certain genodermatoses including epidermolyses and keratinization disorders. We found that chorionic villi have only a few of the characteristics differentiated in skin, and none of the structures which are relevant to the diagnosis of genodermatoses. In our view, the ultrastructural approach is not suitable for first trimester prenatal diagnosis of genodermatoses in chorionic villi.

Have We Neglected the Role of Fetal Endothelium in Transplacental Transport?

“…Maternal‐to‐fetal transfer of nutrients and other substances is complex and accomplished under different physiological conditions, which are determined by nutrient concentrations, utero‐placental and feto‐placental blood flows and oxygenation. The actual transport processes across the PB involve many passive and active mechanisms . Although not directly involved in transport, consumption and storage of nutrients may also modulate the extent of transport.…”

“…The cellular mechanisms involved in transplacental transport in the STB layer have been described in detail in a recent review and include: (i) Passive diffusion, which is governed by Fick's law and may occur with almost any compound with molecular weight less than 500 daltons; (ii) Facilitated or transporter‐mediated diffusion in which passive transport across the STB membranes and along a concentration gradient is enabled by molecular carriers in the STB membrane, for example, GLUTs for glucose or FATPs for fatty acids; (iii) Active transport against a concentration gradient, which requires energy supplied either by ATP hydrolysis (i.e., primary active transport), for example, protons, Ca 2+ and others , or by co‐transporters (i.e., secondary active transport), which themselves are transported down a concentration or electrochemical gradient such as SNATs for amino acids ; (iv) Phagocytosis and pinocytosis in its various forms allows internalization of macromolecules using a range of mechanisms. A well‐known example is the uptake of low‐density‐lipoprotein by receptor‐mediated endocytosis .…”