Correlative light and electron microscopy of dissociated immature rat testicular cells undergoing morphogenesis in vitro

Abstract

Immature rat testicular cells undergo morphogenesis in primary culture (Davis, 1978). Depending upon the number of dissociated testicular cells added to the culture dish, spherical or tubular aggregates were formed. Spherical aggregates resulted from movement of cells into centers of aggregation and the detachment of these cells from the substratum; on the other hand, tubular aggregates resulted from detachment and retraction of the cell monolayer at certain points along its outer edge. In this investigation, the different methods of formation of aggregates by immature rat testicular cells in primary culture were examined with the scanning electron microscope (SEM). The cell types involved in such morphogenesis and their associations within completely formed structures were examined by transmission electron microscopy (TEM). In addition, the rates of formation of aggregates were established by time-lapse cinemicroscopy. During formation of spherical aggregates, the rate of recruitment of cells into centers of aggregation (0.4 +/- 0.006 micrometer/min; means +/- S.E.M., n = 78) was much slower than the rate of cell detachment during formation of tubular aggregates (11.7 +/- 1.8 micrometer/sec; means +/- S.E.M., n = 110). Although specific roles for each cell types in formation of aggregates have not been determined, the associations of cells within the two types of reformed aggregates appeared to be similar. Myofibroblast cells were located in outer cell layers and Sertoli cells were observed to underlie the layers of myofibroblasts in both types of aggregates. Germinal cells, however, were found on the outer surface of spherical aggregates, but in tubular aggregates they were located on the inner surface. Since spherical and tubular aggregates are formed by different methods, this observation suggests that rearrangement of cells, within the aggregates takes place and contributes to the internal morphology of newly formed aggregates.