Cell surface polarization, tight junctions, and eccentric inner cells characterize human teratocarcinoma embryoid bodies

Abstract These studies demonstrate that human embryoid bodies can develop in vitro from human teratocarcinoma cell line HT-H. Furthermore, scanning and transmission electron microscopy reveal that these embryoid bodies resemble the preimplantation embryo more than mouse embryoid bodies which are multilayered. This resemblance is based on (1) an eccentrically located group of inner cells within a thin-walled cyst, (2) apical junction complexes with tight, gap, and desmosomal junctions, as well as intermediate filaments associated with the outer cell layer and not the inner cells, and (3) mitochondria with an extremely dense matrix and few plate-like cristae. Observations of the cell surface indicate that microvilli have a polarized distribution and are localized to two areas (centrally and at intercellular borders) on the apical cell surface of compacted aggregates. Immunosurgery of cystic embryoid bodies indicates that at least half of them are characterized by inner cells enclosed by an impermeable outer cell layer. These developmental similarities with the preimplantation mouse embryo suggest that at least some HT-H teratocarcinoma cells express an embryo-like program for multicellular organization. HT-H embryoid body organization is characteristic of the preimplantation embryo in contrast to the organization reported for mouse embryoid bodies which resembles the postimplantation inner cell mass.