Syncytial units isolated from early human placentas

This morphological study demonstrates that during the early phases of pregn ancy, in the syncytium there are individual multinucleated units joined to one another by junctional complexes which probably are destined to flow tog ether with the main syncytium by membrane breakdown. Normal human placentas from 6(th) to 12(th) 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 nume rous cellular elements from the surface of the free villi. Such isolated el ements have been subjected to centrifugation and separation in Percoll grad ients. 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 fr om different weeks of pregnancy have been considered and the results have b een submitted to statistical analysis. The syncytial units are multinucleat ed and can often be different from one another, particularly in regard to t he characteristics and the number of the nuclei. The evaluation of the numb er of nuclei contained in different syncytial elements shows that nuclei ar e less numerous in the early phases (6-8 weeks) and increase in number towa rds the end of the first trimester in a statistic significant way. In concl usion, the present study could confirm the existence of single syncytial un its, joined to constitute the syncytial layer, probably destined to a compl ete fusion in the main syncytium and likely in functional relationship with the underlying Langhans cells.