Senescence and cytoskeleton: overproduction of vimentin induces senescent-like morphology in human fibroblasts

One characteristic feature of senescent fibroblasts is flat, enlarged, and heterogeneous cell shapes. The present study was aimed to understand the st ructural basis of the senescent cell morphology. SDS-gel electrophoresis as well as western blotting demonstrated that there occurred a prominent prot ein band about 57 kDa in the senescent cells as compared with normal young or immortalized cells growing rapidly, and the protein was identified with a cytoskeletal protein, vimentin. In fact, senescent fibroblasts contained approximately threefold more vimentin protein, and fourfold more vimentin m RNA than young embryonic fibroblasts. In the senescent cells, vimentin cyto skeleton occurred as densely bundled filaments in parallel with the long ax is of cell bodies, whereas in young or actively growing cells it showed sho rt and thin vimentin filaments or fur-like irregular networks. It was furth er demonstrated that senescent cell shapes could be induced when a vimentin expression construct was transfected in young fibroblasts. These results s uggest that senescent fibroblasts overproduce vimentin protein, and the ove rproduced vimentin filaments bring about the senescent cell morphology.