PS-15-007 NCAM polysialylation as potential initiator of differentiation and proliferation of renal progenitors in human fetal tissue S. Cirovic * , J. Tadic, N. Radunovic, C. Müller, G. Müller, J. Markovic-Lipkovski * Inst. for Pathology, Nephropathology, Belgrade, Serbia Objective: Objective: Neural cell adhesion molecule (NCAM) is widely expressed on mesenchymal and early tubular epithelial cells during kidney development although with still undefined function. NCAM can be polysialylated and as PSA-NCAM has been shown to be involved in proliferation and migration of neuronal cells during brain development. The aim of this study was to evaluate the presence of PSA-NCAM in nephron precursors in relation to the expression of renal progenitor and proliferation markers. Method: Human fetal and neonatal kidneys were analyzed using double-immunofluorescence (dIF) staining and Western Blot (WB) analysis. Specific antibodies against NCAM, PSA-NCAM, EpCAM, CD24 and Ki-67 were applied. Results: On WB only fetal tissue samples have bands with NCAM at 140 to 250 kDa which suggest that NCAM molecule is polysialylated; dIF analysis of fetal tissue show PSA-NCAM + Ki-67+ cells in all structures known as nephron precursors. While in neonatal tissue PSA-NCAM and Ki-67 were positive only on rare single cells in intersticium. Conclusion: PSA-NCAM expression appears to characterize a very early stage of induced nephron progenitors differentiating from NCAM + EpCAM-mesenchymal cells. According to PSA-NCAM localization and coexpression with Ki-67 during development and its practically absence in neonatal tissue, suggest that PSA-NCAM present potential initiator of proliferation and differentiation of renal progenitor. Objective: Cystic hygroma (CH) typically develops in utero, late in the first trimester to early in the second trimester of gestation. Many of the fetuses with CH present additional malformations commonly associated with chromosomal anomalies. Method: A review of 548 fetal autopsies performed over a 10 year period revealed 19 cases of CH (3,4 %). The results of cytogenetic analysis and the prenatal ultrasound findings were retrieved and compared to the autopsy findings. Results: Fetal death was due to therapeutic abortion in 9/19 cases, intrauterine death in 8/19 cases, and spontaneous abortion in 2/19 cases. Cytogenetic analysis was available in 12 cases. The results showed an abnormal karyotype in 7 cases (5 cases of Turner syndrome and 2 cases of trisomy 21). The mean size of CH was 5,4 cm. Other findings suggestive of the cause of fetal death were diagnosed in 10/19 cases (52,6 %). The most common autopsy findings were hydrops and central nervous system anomalies. The autopsy findings were in agreement with the prenatal ultrasound findings in 14/19 cases, while in 5 cases (26,3 %) additional findings were detected during autopsy. Conclusion: Our study is confirms the strong correlation between CH and chromosomal anomalies of the fetus.