Analysis of cell populations of normal and injured mouse lens epithelium. I. Cell cycle

Using a combination of single isotope and double isotope autoradiography after injection of ³H-thymidine and of ³H- + ¹⁴C-thymidine, respectively, the cell cycle of normal and injured lens epithelial cells in the mouse was determined. Progenitor cells in the peripheral region of normal lens epithelium were found to traverse the replicative cycle in the same amount of time as the injury-stimulated cells in both peripheral and central (wound) regions. The individual phases were also the same length, except for a slight shortening of G₂ in the injured epithelium. The durations of the phases were: S: 11–12 hours; G₂: 1.5–2 hours; M: 4.2–5 hours; G₁ (derived): 38–44 hours; and total cycle: 55–61 hours. Two findings were significant in view of previous observations that injury to mouse lens seldom induces lens opacity. First, while the cell cycle duration was not affected by injury, a burst of proliferation of potentially active cells ensued. And, secondly, this burst of proliferation involved only one cell cycle. Only a small number of cells, equivalent to the normal progenitor compartment, continued into a second replicative cycle. The wound was healed, therefore, mainly by one division cycle involving a large number of cells.