HCG concentration and receptor gene expression in placental tissue from trisomy 18 and 21

Trisomy 21 is associated with high maternal serum concentrationsof intact human chorionic gonadotrophin (HCG) and free ß-HCGwhereas these concentrations are markedly decreased in trisomy18. In this study, we investigated the effect of trisomy 21and 18 on endogenous HCG concentrations and luteinizing hormone(LH)/HCG receptor expression in placental villous tissue ineight trisomy 21, six trisomy 18 and 42 chromosomally normalsamples, collected at 12–16 weeks gestation. The tissueconcentrations of intact HCG, free -HCG and free ß-HCGsubunits were measured using solid-phase two-site immunoradiometricassay. LH/HCG receptor expression was evaluated with immunohistochemistryand in-situ hybridization. Villous tissue in trisomy 21 containedhigher ß-HCG concentrations than the controls (P <0.05). In trisomy 18 cases, the ß-HCG concentration waslower than in the control group (P < 0.01). Both immunocytochemistryand in-situ hybridization demonstrated a more intense stainingof the trophoblast in cases of trisomy 21 and 18, compared withcontrols with the strongest signal in cases of trisomy 18 (P< 0.01). We concluded that in trisomy 21 the high tissueHCG concentration and expression of LH/HCG receptor in the trophoblastmay reflect the relative immaturity of the trophoblastic tissuewhereas in trisomy 18, the very low concentration of endogenousHCG, associated with an over-expression of LH/HCG receptor inthe trophoblast, is probably secondary to the poor differentiationof the cytotrophoblast. HCG/placenta/pregnancy/receptors/trisomy Notes ⁴ To whom correspondence should be addressed at: Academic Departmentof Obstetrics and Gynaecology, University College London MedicalSchool, 86–96 Chenies Mews, London WC1E 6HX, UK