To have a better understanding of ageing in this second part of the article titled "Ageing and the Increase of Lifespan", cell senescence and the telomere hypothesis will be discussed.
Cell senescence (replicative senescence) is the irreversible state reached by certain cells when they arrest from the cell cycle and do not undergo any other division. During this event a series of morphological cellular changes are produced and this may contribute to tissue ageing.
Telomeres are repeat sequences with double stranded DNA whose ends are loop shaped. These loops are rich in guanine (G) bases that protect the ends of chromosomes. It was discovered, through a technique called population doubling (PD), that during all the rounds that cells experience division, telomeres progressively shorten. This led scientists to think that they were the cause of cell senescence, and consequently were directly implicated in ageing. Nevertheless, after years of investigations, a new telomere hypothesis has arisen.
The Telomere Hypothesis
A first hypothesis suggested that cells become senescent when their telomeres were dramatically shortened. Recently, an alternative proposal has arisen, which states that telomeres merely act as sensors of DNA damage, monitoring, for example, oxidative stress. Indeed, it has been found there are both telomere-dependent and telomere-independent routes to cell senescence.
Five events that can generate cell senescence have in fact been identified: short telomeres, chromatin decondensation, DNA damage, activation of oncogenes and overactivation of mutagenic stimuli. It has thereforebeen suggested, after many experiments increasing and decreasing oxygen levels in cultured cells of mice and humans, that lifespan in cells could be more closely related to oxidative stress than to telomere length.
Other Ventures to Defy Ageing
As genomic knowledge is essential to fight against ageing, some corporations such as Halcyon molecular have decided to find ways to design fast and cheap methods of sequencing genomes. Such techniques will allow scientists to manipulate medical data more easily in order to correct the DNA damage and chromosomal irregularities that occur during ageing.
Moreover, this scientific discovery will allow comparative research to be conducted between humans and other species with extreme lifespans. As an example, data from the tortoises in Galapagos Islands, which can live to 170 years, could be used to implement the extension of human lives.
The pill being developed by Russian scientist Vladimir Skulachev, may be another breakthrough in the battle against ageing. In his statement to the press this chief of the Bioenergetics department of Moscow State University (and dean of the school of Bioengineering and Bioinformatics) explains that he is close to discovering an antioxidant that is able to withstand the conversion of oxygen to a superoxide (a free radical), a toxic substance that makes our cells age. Novel Prize winner, Dr Gunter Blobel from Rockefeller University in the US, fully supports Skulachev's work.
Sources
- Blackburn, EM. (1991) 'Telomeres', Trends in Biochemical Science
- Campisi, J. (2001), 'From Cells to Organisms: Can we Learn About Ageing From Cells in Culture?, Experimental Gerontology
- Harley, CB., Vaziri H., Counter, CM., Allsopp, RC. (1992), 'The Telomere Hypothesis of Cellular Ageing', Experimental Gerontology
- Houben, SM., Moonen, HJ., Van Schoolen, FJ., Hajeman, GJ. (2008), ' Telomere Length Assessment: Biomarker of Chronic Oxidative Stress?', Free Radical Biology and Medicine
- Skulachev, Vladimir. 'Fountain of Youth Pill is Just Two Years Away from Shop Shelves', The Daily Mail, 2010
Dinah JL Novak - Years of hard work within investigative journalism (online, print and TV ), scientific research and academics (BA and BSc) have provided ...
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