Maintenance of multiplication rate stability by cell populations in the face of heterogeneity among individual cells.

We addressed the question of how a population of cells can maintain a constant multiplication rate given the heterogeneity of its individual members. Using the NIH 3T3 line of mouse embryo cells, comparisons were made of multiplication rates between offspring subclones and the parental clones from which the subclones were derived. Parents at all levels of multiplication rate produced offspring with a wide range of multiplication rates. Offspring from parent cells with the highest growth rates rarely exceeded their parents in rate of multiplication. Offspring from slow-growing parents, however, often exceeded the parents. It is concluded that the multiplication of NIH 3T3 populations represents constant diversification in multiplication rate: heterogeneous parents producing heterogeneous offspring. Population growth rates can remain stable because the fastest-growing parents generally produce offspring that multiply slower than the parents while the slowest parents often produce offspring that multiply faster than the parents.