Characterization of human placental explants: morphological, biochemical and physiological studies using first and third trimester placenta

The primary objective of this study was to characterize an in-vitro model o f the human placenta using morphological, biochemical and physiological par ameters. Placental villi were obtained from normal first trimester and term pregnancies. The villi were incubated with Dulbecco's modified Eagle's med ium: Ham's F12 nutrient mixture in a shaking water bath at 37 degrees C for up to 310 min. The viability was determined by the production of beta huma n chorionic gonadotrophin (HCG) and lactic dehydrogenase (LDH) and the inco rporation of [H-3]thymidine, [H-3]Lleucine and L-[(UC)-C-14]arginine, while ultrastructure was assessed by transmission electron microscopy. In the fi rst and third trimester group, the release into the medium of the intracell ular enzyme LDH remained unaltered throughout the experiment. By contrast, beta-HCG concentrations increased linearly and concentrations were higher i n the first trimester than term villi (354.5 +/- 37.8 versus 107 +/- 8.1 IU /g villi protein; P < 0.001). Electron microscopy confirmed preservation of tissue viability for up to 4 h of incubation. The incorporation of thymidi ne (12.2 +/- 2.9 versus 5.2 +/- 0.5 nmol/g villi protein; P < 0.05), leucin e (9.4 +/- 2.1 versus 1.9 +/- 0.4 nmol/g villi protein; P < 0.02) and argin ine (17 +/- 4.4 versus 4.2 +/- 0.5 nmol/g villi protein; P < 0.05) were mar kedly higher in early than in term placenta, Furthermore, placental uptake of Lleucine by the first (9.4 +/- 2.1 versus 17 + 4,4 mmol/g villi protein; P < 0.001) and third trimester placental villi (1.9 +/- 0.4 versus 4.2 + 0 .5 mol/g villi protein; P < 0.001) was less than that of L-arginine, This s tudy describes a simple technique using placental explants to determine rel ative rates of uptake of substrate amino acids throughout gestation.