Zonal differentiation of the marmoset (Callithrix jacchus) endometrium.

The differentiation of the marmoset (Callithrix jacchus) endometrium under different steroid hormone levels was investigated by electron microscopy and by the binding of different antibodies directed against collagen types. Based on differences in the glandular and interglandular compartments, the endometrium of sexually mature common marmosets consists of 3 zones: basal, adluminal and luminal. Hormone-dependent appearances are characterised. With low steroid concentrations, intercellular spaces between glandular epithelial cells occurred in the adluminal and the luminal areas. Epithelial cells of the basal region exhibited coated pits and phagolysosomes together with large apical protrusions. Under oestrogen dominance, phagolysosomes, fat vesicles and apical protrusions were evident in epithelial cells in the adluminal region. Secretory granules and concentric glycogen accumulations were a characteristic feature in epithelial cells of the adluminal and basal regions. With high progesterone concentrations, large empty vesicles were found with a higher frequency in adluminal than in basal epithelial cells. Using FITC-labelled antibodies against types V and VI collagen, binding was apparent adluminally in close vicinity to basement membranes, whereas reactivity was seen in the entire interglandular region of the basal area during this phase. Our findings indicate specific microenvironments with distinctive structural characteristics in the marmoset endometrium that are hormone dependent during all phases of the endometrial cycle. They are not related to menstruation, appear to be characteristic for primates and could reflect epithelial-mesenchymal interaction.