Samrina Mohammad, Muslim Khan.
The Isolation Of Human Senescent Cells By Their Inability To Attach To Fibronectin.
Pak Oral Dental J Jan ;37(1):36-40.

Senescence derived from a Latin word senex means old age. Senescence in an organism's life is a phase of developmental decline, and a loss of replicative capacity in cell culture. Cellular senescence is due to cycle arrest in the G1 phase of the cell cycle in response to physiological levels of mitogens. Senescence is often associated with DNA Damage foci and it involves the cell cycle inhibitors p21WAF and P16INK4A together with other proteins, including senescence-associated b Galactosidases (SAbGal) and several cytokines. The objective of the study was to test whether the senescence of normal human epidermal keratinocytes (NHEK) or the initiation of NHEK differentiation with, or without stratification, leads to reduced adhesion to FN. NHEK underwent three different adhesion experiments and at three different calcium (Ca) concentrations, starting from 0.09mM Ca and then 0.6mM Ca for 5 days and 1.0mMCa for 24 hrs. At all these concentrations cell adhesion time courses were done. The experiments showed that senescence slowed the rate of adhesion of NHEK cells to FN. Also at 0.6mM Ca NHEK differentiation alone did not influence the rate of adhesion to FN, but differentiation along with stratification at 1.0mM Ca did influence the adhesion rate. Ki67 immunofluorescence staining revealed that whilst the senescent and stratified NHEK cultures showed reduced numbers of cycling cells the differentiated cells in 0.6 mM Ca did not. Unlike the situation with oral fibroblasts, we were unable to demonstrate a large enrichment for senescent NHEKs in the floating population at any time point as assessed by SA-bGal staining of the different cell populations. It was concluded that both the later stages of terminal differentiation (stratification) and senescence reduced the adhesion rate of NHEKs to FN but that differentiation alone did not. The reduced rate of adhesion to FN was associated with a reduced number of cycling cells. The inability to enrich for senescent NHEKs using the rate of adhesion to FN may be related to the confounding influence of NHEK terminal differentiation on FN adhesion rates.

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