They are then placed in specialized dishes containing a growth-promoting solution, the cell culture medium. The methods used to release the cells as well as the culture medium allow selection of the growth of a particular cell type and the establishment of the cell culture. Many researchers utilize the cell culture model system, and it has been yielding new insights into the basic molecular processes of human biology and aging. He studied human fibroblastlike cells obtained from lung and skin. Fibroblast cells are spindle shaped and are important in maintaining the matrix, the material around all cells, in these tissues.
Fibroblast cells produce proteins such as collagens and fibronectin, which make the matrix.
Hayflick found that when serially cultured, these cells would undergo rounds of divisions, but as the culture aged, the cells were no longer able to divide. In conjunction with the loss of division potential, there were changes in the morphology, the shape and physical appearance, of cells. The cells enlarged significantly, and more space was observed between individual cells. Hayflick did a number of experiments to demonstrate that the cell senescence model was not an artifact of putting cells in culture. These experiments included using culture medium from senescent cells to demonstrate that the medium could still support the growth of young cultures.