Shape and Movement of Mesenchyme Cells as Functions of the Physical Structure of the Medium

Abstract

Heart fibroblasts representing a single cell type were grown in culture media composed of mixtures of fowl plasma and chick embryo extract. In the first set of expts. varying ratios of the 2 components were used, ranging from 10-90% plasma concn. with a corresponding increase in size of fibrin bundles. In the 2d set plasma and extract were mixed in equal amts. (40% plasma concn.), but coagulated over a pH range from 5.6-8.0. The physical texture of the medium was thereby graded, since the lower the pH, the coarser the fibrin bundles. 4759 cells taken at random were measured in camera lucida drawings of either the living cultures or fixed prepns. The index of elongation for the cell was obtained by the ratio of length/width, and for the nucleus by the ratio of longest/shortest nuclear diameter. An increasing proportion of elongate (bipolar) cells and a correspondingly decreasing proportion of stellate (multipolar) cells occurred with increasing size of the fibrin bundles (higher plasma concns. or lower pH values). The index of elongation for both the cell and the nucleus increased non-linearly with increasing plasma concn. or decreasing pH values. The rate of migration for 1582 cells was detd. by tracing cells at the margin of a culture after 24 and 48 hrs. of cultivation. Values for the avg. rates and also for the 10 fastest cells indicated that the migration rate increased rapidly with increasing plasma concn. to a max. of approx. 1 mm./day with a plasma concn. of 40%. This rate was maintained quite constantly at higher plasma concns. The slower migration at lower plasma concns. was explained by the competing cell projections of the predominantly multipolar cells which caused delays in progress and deviations from a linear course. The bipolar cells predominating at higher plasma concns. would glide in a straight pathway at a constant velocity. Actually the rate of protoplasmic motion might have been the same in both groups. The theoretical implications of these results are discussed and also the possibility of testing different cell strains against a constant environment. Caution is advised in the use of tissue cultures as a means of assaying growth stimulants and inhibitors, because of the relationship involving the texture of the medium, cell configuration and cell growth, and the possible effect of the agent on any of these.