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Early-Senescing Human Skin Fibroblasts Do Not Demonstrate Accelerated Telomere Shortening

Marina Ferenac¹, Denis Polanec², Miljenko Huzak³, Olivia M. Pereira-Smith⁴ and Ivica Rubelj^1,

¹ Department of Molecular Biology, Ruer Bokovi Institute, Zagreb, Croatia.
² PLIVA-Research Institute Ltd., Biology, Flow Cytometry and Cell Sorting Lab, Zagreb, Croatia.
³ Department of Mathematics, University of Zagreb, Croatia.
⁴ Department of Cellular and Structural Biology, Sam and Ann Barshop Center for Longevity and Aging Studies, San Antonio, Texas.

Address correspondence to Ivica Rubelj, PhD, Department of Molecular Biology, Ruer Bokovi Institute, Bijenika 54, Zagreb 10000, Croatia. E-mail: rubelj{at}rudjer.irb.hr

Most normal mammalian cell lines demonstrate limited growth capacity due to the gradual accumulation of senescent cells in the culture. Senescent cells appear initially at a low incidence, but with increasing frequency as the culture accumulates more divisions. Because it has been suggested that senescence is regulated by telomere shortening in human cells, we compared the telomere lengths of the subpopulation of senescent cells, present in presenescent cultures, with those of young cells. Senescent cells were separated from young cycling cells by either bromodeoxyuridine (BrdU) incorporation followed by Hoechst dye and light treatment or DiI staining followed by separation on a high-speed cell sorter. Our results demonstrate that telomeres of early-senescing cells are the same length, and must shorten at the same rate, as cycling sister cells in the culture. Therefore, senescent cells in young mass cultures occur as a result of a stochastic, nontelomere-dependent process that we have described: sudden senescence syndrome.