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Axin-1 expression in normal and IUGR placentas

Axin-1 is important component of Wnt signaling pathway that binds to Adenomatous Polyposis Coli (APC) protein thus enabling phosphorylation of β catenin by glycogen synthase kinase-3β. This phosphorylation is crucial step for proteomic degradation of β catenin hence the most important role of axin is negative regulation of Wnt signalling pathway and a reason to believe it is tumor supressor gene. Wnt pathway is very important in the development of the normal and pathological pregnancies. The aim of this study was to investigate the axin-1 expression in human placentas of normal pregnancies and compare it with placentas of pregnancies complicated with intrauterine growth restriction (IUGR). Twelve placentas, gestational age 31st week to 40th week of normal pregnancies were compared with 10 IUGR placentas of matching gestational age. IUGR diagnosis was based on series of ultrasound examinations during antenatal care with strict exclusion criteria. Fetal weight under 5th percentile adjusted for sex, gestational age and parity according to the national standards was considered significant for IUGR. Additional diagnostic criterion was abnormal Doppler velocity waveforms of umbilical and medial cerebral artery. We used rabbit anti human axin-1 polyclonal antibody (Zymed Labaratories Inc., San Francisco, USA) for immunohistochemical staining. Axin-1 staining density was analyzed by Image Analyzer SFORM (Vamstec). Detected light intensity is reversely proportional to staining results i.e. protein expressed. The measurements were performed at magnification x100 on 10 consequtive views in the central area of histological section. Non-parametric statistics (Mann-Whitney) were used to compare the results between two groups of placentas. Immunohistochemistry revealed axin-1 located mostly in cytoplasm of syncytiotrophoblast and to a lesser extent in its nuclei of both groups. Quantification of staining showed statistically greater density and distribution of axin-1 expression in IUGR placentas (p<0.05). Higher expression of axin-1 in IUGR placentas in comparison to normal placentas indicate a role of Wnt signalling pathway in placental developmental pathology.

Wnt signaling pathway; placenta

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