The architecture of first trimester chorionic villous vascularization: a confocal laser scanning microscopical study.

BACKGROUND: The aim of this study was to investigate normal chorionic villous vascularization using CD31 immunofluorescence and confocal laser scanning microscopy (CLSM) to elucidate the spatial arrangement in terms of connections between vessels and cords and their branching patterns compared to deficient chorionic villous vascularization in complicated pregnancies. METHODS: A descriptive morphologic study using CLSM after CD31 immunofluorescence staining of placental biopsies from normal pregnancies (n = 20), complete hydatidiform molar pregnancies (CHMs; n = 3) and empty sacs (n = 3), with a well documented gestational age (GA). RESULTS: In this three-dimensional study, first trimester chorionic villi were occupied by a complex network of mainly cords with redundant connections as early as 5(+5) weeks GA. With increasing GA cords transform into vessels. From about 9 weeks GA onwards, vascular development is characterized by the presence of two large vessels located centrally and surrounded by and connected to a capillary network. In first trimester CHM and empty sacs, we observed a primitive network of mainly cords. CONCLUSIONS: This first visualization of the spatio-temporal patterns of blood vessel formation in placental villi is characterized by the development of the vasculosyncytial membrane from a complex network of cords and can be regarded as the placental development before it becomes functional at the end of organogenesis.

Histological classification of chorionic villous vascularization in early pregnancy.

BACKGROUND: The objective of the study was to assess the reproducibility of a new classification for early pregnancy chorionic villous vascularization (Grade: I, normal; IIA, mild hypoplasia; IIB, severe hypoplasia and III, avascular) for routine microscopic examination in daily clinical practice. METHODS: In this observational study, four observers scored first trimester chorionic villous vascularization. Scoring was performed in microscopic slides of chorionic tissue obtained by D&C in 30 patients with early pregnancy loss due to empty sac (n = 10), fetal death (n = 10) and termination of pregnancy (n = 10) using the new classification. Ultrasonographic measurement of trophoblastic thickness (TT) at the implantation site was available in all patients and in a reference group of 100 ongoing singleton pregnancies. The vascularization score could therefore be related to the TT. RESULTS: The new classification resulted in a good-to-excellent agreement in histological scoring (0.73-0.90) between investigators (kappa 0.64-0.86). TT was not related to either vascularization or pregnancy outcome and only partly to hydropic degeneration. CONCLUSION: The vascularization scoring system is a simple, valid and effective method for assessment of chorionic villous vascularization. It is helpful in understanding the underlying cause of pregnancy loss, as the classification can distinguish between normal and abnormal embryonic development. We did not find either a relation between TT and pregnancy outcome or between TT and vascularization.

Vasculogenesis in complete and partial hydatidiform mole pregnancies studied with CD34 immunohistochemistry.

BACKGROUND: Defective chorionic villous vascularization is present in pregnancies complicated by absent or abnormal embryonic development. The aim of this study was to investigate the embryonic and/or maternal genomic influence on vasculogenesis in diploid complete hydatidiform mole (CHM) and in triploid partial hydatidiform mole (PHM) in comparison with normal development. METHODS: Mean villous stromal area and functional vascular area, vessels with a lumen and haemangiogenetic cords, peripherally or centrally located were measured and counted in chorionic villi of 12 CHM, 12 normal pregnancies (termination of pregnancy, TOP) and 15 PHM of which nine were without an embryo (PHM-E) and six were with an embryo (PHM + E), using quantitative CD34 immunohistochemistry. RESULTS: TOP showed significantly more vessels per chorionic villus, centrally and peripherally located (median, range), than CHM, PHM-E and PHM + E (4.0, 0-9 versus 0.0, 0-11, 0.0, 0-18 and 1.0, 0-21). CHM showed significantly more centrally located cords than PHM-E, PHM + E and TOP (1.5, 0-22 versus 1.0, 0-15, 0.5, 0-8 and 1.0, 0-2). CONCLUSIONS: Initiation of chorionic villous vasculogenesis is independent of the maternal genome (CHM). The development of an embryo, however, is obligatory for the modulation of normal vascularization resulting in a well developed vasculosyncytial membrane.