Ultrastructure of Placenta of Gravidas with Gestational Diabetes Mellitus

Abstract

Objectives. Gestational diabetes mellitus (GDM) leads to an abnormal placental environment which may cause some structural alterations of placenta and affect placental development and function. In this study, the ultrastructural appearances of term placentas from women with GDM and normal pregnancy were meticulously compared. Materials and Methods. The placenta tissues of term birth from 10 women with GDM and 10 women with normal pregnancy were applied with the signed informed consent. The morphology of fetomaternal interface of placenta was examined using light microscopy (LM) and transmission electron microscopy (TEM). Results. On LM, the following morphological changes in villous tissues were found in the GDM placentas when compared with the control placentas: edematous stroma, apparent increase in the number of syncytial knots, and perivillous fibrin deposition. On TEM, the distinct ultrastructural alterations indicating the degeneration of terminal villi were found in the GDM placentas as follows: thickening of the basal membrane (BM) of vasculosyncytial membrane (VSM) and the VSM itself, significantly fewer or even absent syncytiotrophoblastic microvilli, swollen or completely destroyed mitochondria and endoplasmic reticulum, and syncytiotrophoblasts with multiple vacuoles. Conclusion. Ultrastructural differences exist between GDM and control placentas. The differences of placenta ultrastructure are likely responsible for the impairment of placental barrier and function in GDM.

Figure 1

Pathological morphology of placentas from control group (a, b) and GDM group (c, d). Placental sections were HE-stained. (a) The normal branching of villous trees. (b) The syncytiotrophoblast (ST) was clearly observed lying outside the villi, with scarce single cells of cytotrophoblast (CT). (c and d) The increased syncytial knotting (∗), villous edema (arrows), and perivillous fibrin (fi) depositions in GDM group. Bar = 20 um.

Figure 2

Ultrastructure of placentas from control group (a–c, g–i) and GDM group (d–f, j–l) observed using a JEM-1010 electron microscope. TEM images showed at different magnifications (×5000 (a and d), ×12 000 (b and e), and ×25 000 (c and f)). (a–c) Normal placental barriers were displayed in control, VSM, composed of the outer layer ST with a multitude of microvilli (MV) on the surface, fetal capillaries with fetal blood cells inside, and BM and interspaces between them. (d–f) In GDM group, intact placental barriers were apparent along with degenerative alterations of the terminal villi, mainly in VSM and BM, including thicker placental barriers, decreased apical microvilli, and increased multiple vacuoles (V) in ST. Bar = 5 um (a and d), 2 um (b and e), and 1 um (c and f). (g–i) Mitochondria (g), cytoplasmic vacuoles (h), and ER (i) with normal appearance in the cytoplasm of ST in control group. (j) The massive swelling, even ridge deprivation, and architectural disruption of mitochondria (m) in the GDM placenta. (k) The massive cytoplasmic vacuoles accumulation in the ST of GDM placenta. (l) The dilation of endoplasmic reticulum (ER) cisternae in GDM group. Bar = 500 nm (g and j), 2 um (h and k), and 1 um (i and l).

Figure 3

Comparison of semiquantitative parameters of placental ultrastructures between GDM and control group. (a–c) The terminal villi of GDM (a) and control (b) placenta. (c) Placental barrier thickness (arrow) of GDM group (6746.15 ± 1270.22 nm, n = 10) was significantly thicker than that of control group (4591.34 ± 1178.60 nm, n = 10; P < 0.05). Bar = 5 um. (d–f) The terminal villi of GDM (d) and control (e) placenta. (f) The BM of ST in GDM group (1077.49 ± 194.39 nm nm, n = 10) was thicker than that in control group (707.54 ± 256.56 nm, n = 10; P < 0.05). Bar = 1 um. (g–i) The density of ST apical microvilli in GDM (g) and control (h) placenta. (i) The density of ST apical microvilli in GDM group (44.36 ± 21.95 per 10 um, n = 10) was significantly lower than that in control group (77.13 ± 20.82 per 10 um, n = 10; P < 0.05) and even microvilli-free in some areas. Bar = 2 um.