Dynamics of L-929 cell spreading after mitosis

Changes in the cell shape of L-929 (NCTC, clone 929) during the cell cycle were analyzed with time-lapse microscopy. It was found that the cells pass through three spreading stages. The maximal cell spreading was observed during the first 1.5 h after mitosis. In this period, the cell area increases in correspondence with the sigmoid dependence and enlarges by approximately 3.0–3.5 times. After a short plateau, the cell area begins to increase, also correspondence with the sigmoid dependence. This period is longer (up to 6 h after the beginning of cell division), with an additional 1.5-fold increase in the cell size. Later, cell area enlargement continues linearly up to the beginning of the next mitosis. After the mother L-929 cell division, almost 100% of daughter cells remained to be bridged together in the site of the division furrow. Connected L-929 cells spread and migrate for 2.13 ± 0.06 h and then separate. The daughter-cell shape transition from round to the spread one and simultaneous maintenance of the intercellular bridge during a strictly determined time allows us to consider this phenomenon as independent and not related to mitosis. We suggest designating this junction between the daughter cells as the “posttelophase intercellular bridge.”