Kinetics of cell replication in the uterine cervix. VI. Loci of DNA-synthesizing cells and arrested mitoses in the basal-cell layer.

The mode of proliferation in the basal-cell layer of the squamous cervical epithelium was investigated in C57B1 mice with the aid of 3H-thymidine and vincristine. Six hours after vincristine injection and two hours after thymidine injection, 33% of the basal cells were in DNA synthesis and 12% in mitosis. Of these, only 23% of the cells in DNA synthesis and 45% of those in mitosis were found as single cells. The remaining cells proliferated in clusters of two or more cells. As many as 59% of the cells in DNA synthesis and 30% of those in mitosis occurred in colonies of three or more consecutive cells, indicating that multicell clustering is a rather common pattern of basal cell proliferation. Multicell loci of DNA-synthesizing cells occurred contemporaneously with but independently of multicell loci of mitotic cells (the loci were nonconsecutive). Basal-cell replication in the squamous cervical epithelium thus appears to be an organized process of cell renewal.