Effects of surface substances of untransformed fibroblastic cells on the adhesion and proliferation of neighboring cells : a study using fixed confluent cell sheets

To study the effects of surface materials of cells on the behavior of other neighboring cells in a crowded culture, con fluent sheets of rat 3Y1 fibroblasts were fixed and then 3Y1 cells were seeded on to them. Among con fluent sheets un fixed, fixed with formalin and fixed with ethanol and an empty plastic dish surface, the substrate activity to permit cell adhesion was compared. After con fluent 3Y1 cells (mainly composed of cells with a G1-DNA content) were reseeded with fresh medium on to these substrates, the capacity to initiate DNA synthesis per attached cell was also compared. The substrate activity of the ethanol-fixed cell sheet to permit cell adhesion was as high as that of the empty dish surface, whereas that of the un fixed cell sheet and that of the formalin- fixed cell sheet were low. When the ethanol-fixed cell sheet and the empty dish surface were coated with the ethanol extract of the un fixed cell sheet, the substrate activity diminished, indicating that during the fixation process with ethanol an adhesion-inhibitory factor (s) was removed. The capacity to initiate DNA synthesis of each cell that had completed adhesion and spreading on the cell sheets un fixed, fixed with formalin, and fixed with ethanol was lower compared to the cell that had adhered to the empty dish surface. We conclude that factors over the 3Y1 cell surface inhibit the overlapping cell adhesion and the proliferation of cells contacting each other, resulting in the ordered cell configuration in the con fluent culture.