Syncytial units isolated from early human placentas

This morphological study demonstrates that during the early phases of pregnancy, in the syncytium there are individual multinucleated units joined to one another by junctional complexes which probably are destined to flow together with the main syncytium by membrane breakdown. Normal human placentas from 6th to 12th week of pregnancy, derived from voluntary abortions, have been utilized. According to the method described by Tedde et al. (1991), clusters of villi have been isolated, washed in saline and subjected to a treatment with a 0.3% trypsin solution that caused the detachment of numerous cellular elements from the surface of the free villi. Such isolated elements have been subjected to centrifugation and separation in Percoll gradients. Then multinucleated syncytial units have been collected, attached to slides by cytocentrifugation, stained with toluidine blue, observed at the light microscope and utilized to count their nuclei: about 600 elements from different weeks of pregnancy have been considered and the results have been submitted to statistical analysis. The svncytial units are multinucleated and can often be different from one another, particularly in regard to the characteristics and the number of the nuclei. The evaluation of the number of nuclei contained in different syncytial elements shows that nuclei are less numerous in the early phases (6-8 weeks) and increase in number towards the end of the first trimester in a statistic significant way. In conclusion, the present study could confirm the existence of single syncytial units, joined to constitute the syncytial layer, probably destined to a complete fusion in the main syncytium and likely in functional relationship with the underlying Langhans cells.