The in vitro kinetics of senescence of Fischer 344 rat embryo fibroblasts

Oxidative stress, antioxidants, hormesis and calorie restriction: The current perspective in the biology of aging

Aging, in a large measure, has long been defined as the resultant of oxidative stress acting on the cells. The cellular machinery eventually malfunctions at the basic level by the damage from the processes of oxidation and the system starts slowing down because of intrinsic eroding. To understand the initial destruction at the cellular level spreading outward to affect tissues, organs and the organism, the relationship between molecular damage and oxidative stress is required to understand. Retarding the aging process is a matter of cumulatively decreasing the rate of oxidative damage to the cellular machinery. Along with the genetic reasons, the decrease of oxidative stress is somehow a matter of lifestyle and importantly of diet. In the current review, the theories of aging and the understanding of various levels of molecular damage by oxidative stress have been emphasized. A broader understanding of mechanisms of aging have been elaborated in terms of effects of oxidative at molecular, mitochondrial, cellular and organ levels. The antioxidants supplementation, hormesis and calorie restriction as the prominent anti-aging strategies have also been discussed. The relevance and the efficacy of the antiaging strategies at system level have also been presented.

Quantitative assessment of markers for cell senescence

Cellular senescence, the irreversible loss of replicative capacity, might be a tumour suppressor and a contributor to age-related loss of tissue function. The absence of quantitative tests for reliability of candidate markers for senescent cells is a major drawback in cell population studies. Fibroblasts in culture constitute mixed populations of proliferation-competent and senescent cells, with transition between these with increasing population doublings (PD). We estimated senescent fraction in human and mouse fibroblasts with high precision from easily observed growth curves using a dynamic simulation model. We also determined senescent fractions, at various PD (over a wide range of senescent cell frequencies) using candidate senescence markers: Ki67, p21 (CDKN1A), γH2AX, SAHF and Sen-β-Gal either alone or in combination, and compared with those derived from growth curves. This comparison allowed ranking of candidate markers. High rankings were obtained for Sen-β-Gal, SAHFs and the combination of Ki67 negativity with high (>5 per nucleus) γH2A.X foci density in MRC5 fibroblasts. We demonstrate that this latter marker combination, which can easily be performed in paraffin-embedded tissue, gives quantitative senescent cell frequency estimates in mouse embryonic fibroblast cultures and in mouse intestinal sections. The technique presented is a framework for quantitative assessment of markers for senescence.