Regulation of the density of spermatogonia in the seminiferous epithelium of the Chinese hamster: I. Undifferentiated spermatogonia

Abstract

The topographical arrangement of the clones of A_single, A_paired, and A_aligned (A_s, A_pr, and A_al) spermatogonia on the basement membrane of seminiferous tubules of the Chinese hamster was studied. It was found that at least some of these clones are not distributed at random as clones of similar cell number were often seen in clusters. Areas were found with few or many A_s spermatogonia. Also, clusters of A_pr spermatogonia were found, indicating that in such an area many A_s spermatogonia more or less synchronously formed A_pr spermatogonia. Since clusters of clones of 16 A_al spermatogonia were observed, it can be concluded that these clusters of A_pr spermatogonia may proliferate in at least a roughly synchronous way. It was found that over large areas the densities of undifferentiated spermatogonia may be very low or high in comparison to the mean density in the animal. Whether the ratio of self-renewal and differentiation of the stem cells changed locally in response to the high or low density of undifferentiated spermatogonia in particular areas was investigated. No indications for a regulatory mechanism to keep the density of stem cells and/or the density of undifferentiated spermatogonial clones at a certain level could be detected in the normal Chinese hamster. This lack of regulation was at least partly responsible for the widely different numbers of A₁ spermatogonia that were formed in the various areas studied in stage IX.