Hum. Reprod. Advance Access originally published online on September 14, 2007
Human Reproduction 2007 22(11):2814-2823; doi:10.1093/humrep/dem284
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Histochemical and morphological examination of proliferation and apoptosis in human first trimester villous trophoblast
Department of Physiology, All India Institute of Medical Sciences, New Delhi 110029, India
1 Correspondence address. Tel: +91-11-2659-4625; Fax: +91-11-2658-8641/2658-8663; E-mail: jsen47{at}gmail.com
BACKGROUND: Our present knowledge about trophoblast turnover in human first trimester placental villi based on multiparametric examination of proliferation and apoptosis is limited.
METHODS: Human villous placentae collected during 6, 7 and 8 weeks (n = 10/each group) of gestation were examined for trophoblast proliferation and apoptosis based on quantitative analyses of immunopositive Fas, tumor necrosis factor receptor 1 (TNFR1), cytokeratin 18 fragment (18f), number of proliferating cell nuclear antigen (PCNA), Ki67 and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) positive nuclei, scores of mitotic and apoptotic indices and ultrastructural characteristics.
RESULTS: Mitotic index in cytotrophoblast higher (P < 0.05) at 6 week compared with 7 and 8 weeks of gestation showed significant (P < 0.05) negative correlation between its prevalence and gestational age. Syncytiotrophoblast exhibited higher number of TUNEL positive nuclei (P < 0.01), TUNEL positive apoptotic nuclei (P < 0.05) and apoptotic index (P < 0.05) compared with cytotrophoblast at same gestational age. Positive correlations found between cytokeratin 18f and apoptotic index (P < 0.01), Fas and apoptotic index (P < 0.01), TUNEL positive nuclei and apoptotic index (P < 0.05), cytokeratin 18f and Fas (P < 0.01), whereas cytokeratin 18f (P < 0.05) and Fas (P < 0.05) showed positive correlation only with TUNEL positive apoptotic nuclear data. Phalangeal intrusions of syncytiotrophoblast between transitional cytotrophoblasts showed apposed plasma membranes bearing thickened membrane leaflets, inter-membranous gaps enclosing membranous invaginations, liposome-like particles; patches of membrane seen to be dissolved resulting in cytoplasmic continuity typical of syncytial formation.
CONCLUSION: Cellular remodeling of first trimester villous placenta requires a complex homeodynamics involving proliferation in cytotrophoblast, development-associated syncytialization and apoptosis in syncytiotrophoblast.
Key words: apoptosis/cytotrophoblast/syncytial formation/proliferation/syncytiotrophoblast
Submitted on May 15, 2007; resubmitted on July 31, 2007; accepted on August 17, 2007.