In the interest of clearer communication

Simple Detection Methods for Senescent Cells: Opportunities and Challenges

Cellular senescence, the irreversible growth arrest of cells from conditional renewal populations combined with a radical shift in their phenotype, is a hallmark of ageing in some mammalian species. In the light of this, interest in the detection of senescent cells in different tissues and different species is increasing. However much of the prior work in this area is heavily slanted towards studies conducted in humans and rodents; and in these species most studies concern primary fibroblasts or cancer cell lines rendered senescent through exposure to a variety of stressors. Complex techniques are now available for the detailed analysis of senescence in these systems. But, rather than focussing on these methods this review instead examines techniques for the simple and reproducible detection of senescent cells. Intended primary for the non-specialist who wishes to quickly detect senescent cells in tissues or species which may lack a significant evidence base on the phenomenon it emphasises the power of the original techniques used to demonstrate the senescence of cells, their interrelationship with other markers and their potential to inform on the senescent state in new species and archival specimens.

The origin of transformed cells. studies of spontaneous and induced cell transformation in cell cultures from marsupials, a snail, and human amniocytes

Transformation of cells in culture is a model system for carcinogenesis, and two major theories (i.e., mutagenesis and aneuploidy) have emerged from in vitro and in vivo studies. A third view is presented here on the initial steps in the change of primary cells to extended life cells, and their change to immortalized cells. Both changes involve identical, microscopically visible cell abnormalities hitherto dismissed as cell degenerative characteristics. The major cell changes (i.e., giant cells, nuclear fragmentation to form multinucleated cells [MNC]) translated into genetic terms begin with the creation of polyploidy by DNA endoreduplication, followed by amitotic division of these giant cells to produce MNC. Individual nuclei, surrounded by a cell membrane, bud from the surface of the MNC, and represent the origin of the transformed cells. Induced budding by a protease treatment of MNC suggests that the extracellular matrix is an inhibitor of the budding process from human MNC. The production of the MNC is a genetic process determined by two abnormal events (i.e., overproduction of DNA and amitotic chromosomal segregation) during which there are possibilities for different genetic mechanisms to produce inherited variability within and between MNC. These concepts are discussed in regard to carcinogenesis, and by extension its possible prevention by use of the special cytopathic cell changes in carcinogen testing and in clinical screening programs.