Scientists successfully test first gene therapy against aging-associated decline

May 14, 2012

A number of studies have shown that it is possible to lengthen the average life of individuals of many species, including mammals, by acting on specific genes. To date, however, this has meant altering the animals' genes permanently from the embryonic stage – an approach impracticable in humans. Researchers at the Spanish National Cancer Research Centre (CNIO), led by its director María Blasco, have proved that mouse lifespan can be extended by the application in adult life of a single treatment acting directly on the animal's genes. And they have done so using gene therapy, a strategy never before employed to combat ageing. The therapy has been found to be safe and effective in mice.

The results are published today in the journal EMBO Molecular Medicine. The CNIO team, in collaboration with Eduard Ayuso and Fátima Bosch of the Centre of Animal Biotechnology and Gene Therapy at the Universitat Autònoma de Barcelona (UAB), treated adult (one-year-old) and aged (two-year-old) mice, with the gene therapy delivering a "rejuvenating" effect in both cases, according to the authors.

Mice treated at the age of one lived longer by 24% on average, and those treated at the age of two, by 13%. The therapy, furthermore, produced an appreciable improvement in the animals' health, delaying the onset of age-related diseases – like osteoporosis and insulin resistance – and achieving improved readings on ageing indicators like neuromuscular coordination.

The gene therapy utilised consisted of treating the animals with a DNA-modified virus, the viral having been replaced by those of the telomerase enzyme, with a key role in ageing. Telomerase repairs the extremes of chromosomes, known as telomeres, and in doing so slows the cell's and therefore the body's biological clock. When the animal is infected, the virus acts as a vehicle depositing the telomerase gene in the cells.

This study "shows that it is possible to develop a telomerase-based anti-ageing gene therapy without increasing the incidence of cancer", the authors affirm. "Aged organisms accumulate damage in their DNA due to telomere shortening, [this study] finds that a gene therapy based on telomerase production can repair or delay this kind of damage", they add.

'Resetting' the biological clock

Telomeres are the caps that protect the end of chromosomes, but they cannot do so indefinitely: each time the cell divides the telomeres get shorter, until they are so short that they lose all functionality. The cell, as a result, stops dividing and ages or dies. Telomerase gets round this by preventing telomeres from shortening or even rebuilding them. What it does, in essence, is stop or reset the cell's biological clock.

But in most cells the telomerase gene is only active before birth; the cells of an adult organism, with few exceptions, have no telomerase. The exceptions in question are adult stem cells and cancer cells, which divide limitlessly and are therefore immortal – in fact several studies have shown that telomerase expression is the key to the immortality of tumour cells.

It is precisely this risk of promoting tumour development that has set back the investigation of telomerase-based anti-ageing therapies.

In 2007, Blasco's group proved that it was feasible to prolong the lives of transgenic mice, whose genome had been permanently altered at the , by causing their cells to express telomerase and, also, extra copies of cancer-resistant genes. These animals live 40% longer than is normal and do not develop cancer.

The mice subjected to the gene therapy now under test are likewise free of cancer. Researchers believe this is because the therapy begins when the animals are adult so do not have time to accumulate sufficient number of aberrant divisions for tumours to appear.

Also important is the kind of virus employed to carry the telomerase gene to the cells. The authors selected demonstrably safe viruses that have been successfully used in gene therapy treatment of haemophilia and eye disease. Specifically, they are non-replicating viruses derived from others that are non-pathogenic in humans.

This study is viewed primarily as "a proof-of-principle that telomerase is a feasible and generally safe approach to improve healthspan and treat disorders associated with short telomeres", state Virginia Boccardi (Second University of Naples) and Utz Herbig (New Jersey Medical School-University Hospital Cancer Centre) in a commentary published in the same journal.

Although this therapy may not find application as an anti-ageing treatment in humans, in the short term at least, it could open up a new treatment option for ailments linked with the presence in tissue of abnormally short telomeres, as in some cases of human pulmonary fibrosis.

More healthy years

As Blasco says, "ageing is not currently regarded as a disease, but researchers tend increasingly to view it as the common origin of conditions like insulin resistance or cardiovascular disease, whose incidence rises with age. In treating cell ageing, we could prevent these diseases".

With regard to the therapy under testing, Bosch explains: "Because the vector we use expresses the target gene (telomerase) over a long period, we were able to apply a single treatment. This might be the only practical solution for an anti-ageing therapy, since other strategies would require the drug to be administered over the patient's lifetime, multiplying the risk of adverse effects".

Explore further: Research reveals how cancer-driving enzyme works

Related Stories

Research reveals how cancer-driving enzyme works

May 6, 2011
Cancer researchers at UT Southwestern Medical Center are helping unlock the cellular-level function of the telomerase enzyme, which is linked to the disease's growth.

Study explores possible 'safe and effective' anti-cancer therapy

February 3, 2012
(Medical Xpress) -- New findings discovered by an international research team, which includes a professor from Western University, may lead to a safe and effective anti-cancer therapy.    A report published online ...

Scientists capture single cancer molecules at work

December 8, 2011
Researchers have revealed how a molecule called telomerase contributes to the control of the integrity of our genetic code, and when it is involved in the deregulation of the code, its important role in the development of ...

Recommended for you

Forgotten strands of DNA initiate the development of immune cells

September 21, 2017
Intricate human physiological features such as the immune system require exquisite formation and timing to develop properly. Genetic elements must be activated at just the right moment, across vast distances of genomic space.

Genome editing reveals role of gene important for human embryo development

September 20, 2017
Researchers have used genome editing technology to reveal the role of a key gene in human embryos in the first few days of development. This is the first time that genome editing has been used to study gene function in human ...

A piece of the puzzle: Eight autism-related mutations in one gene

September 19, 2017
Scientists have identified a hotspot for autism-related mutations in a single gene.

Scientists identify key regulator of male fertility

September 19, 2017
When it comes to male reproductive fertility, timing is everything. Now scientists are finding new details on how disruption of this timing may contribute to male infertility or congenital illness.

New assay leads to step toward gene therapy for deaf patients

September 18, 2017
Scientists at Oregon State University have taken an important step toward gene therapy for deaf patients by developing a way to better study a large protein essential for hearing and finding a truncated version of it.

A new approach to high insulin levels

September 18, 2017
Diabetes is characterised by a deficiency of insulin. Its opposite is a condition called congenital hyperinsulinism—patients produce the hormone too frequently and in excessive quantities, even if they haven't eaten any ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Birger
not rated yet May 15, 2012
The key phrase is "without increasing the incidence of cancer".
Now, time to go on to larger mammals...

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.