Diagnostic significance of histopathological assessment of villous extracellular matrix in normal and pathological placentas

OBJECTIVES: The extracellular matrix of chorionic villi is an important factor ensuring the structural and functional viability of the placenta. The aim of the study was to compare the collagen-elastic frame of different types of chorionic villi in normal and pathological pregnancy in the I-III trimesters. METHODS: We compared placentas of the I, II and III trimesters in pathological pregnancies associated with (1) fetal and placental malformations/genetic aberrations/dysgenesis, as well as (2) chronic fetoplacental hypoxia/asphyxia with the group of placentas from uncomplicated pregnancies of the appropriate gestational period. The study was performed by light microscopy on sections stained by Weigert (elastic fibers), Masson's trichrome (type I collagen) and Gomori's silver staining (type III collagen). RESULTS: Physiological pregnancies showed stage-specific remodeling of the collagen-elastic frame. The dominance of the reticular organization of the stroma decreased as the villi matured. At the same time, the proportion of collagen fibrillar structures increased and was accompanied by the relative decrease in the number of subtrophoblastic elastic fibers in the distal, mainly terminal villi. The persistence of diffuse fibrillar and elastic stromal patterns in the terminal villi of full-term placentas was observed with delayed maturation of the villi and diabetes-associated changes in the placenta. Peripheral granular pattern of elastic fiber distribution in aberrant hydropic and dysmorphic villi was detected in fetal and placental malformations, genetic abnormalities, and dysgenesis. A diffuse homogeneous type I collagen pattern was associated with impaired fetoplacental unit formation and hypoxic damage. CONCLUSIONS: Placentas of the I-III trimester with disorders of the formation of the fetoplacental unit, dysmetabolic conditions and hypoxic damage demonstrate patterns of remodeling of the collagen-elastic framework of chorionic villi, which differ from normal placentas of the corresponding gestational age.