Eternal youth could be one step closer.

A woman from Seattle claims to have become the first human to have become younger using gene therapy.

Elizabeth Parrish, CEO of controversial firm Bioviva, says she has been using her own company's experimental gene therapies to battle ageing - but not everyone is convinced of the results.

Scroll down for video

Elizabeth Parrish, CEO of Bioviva, has been using her own company's experimental therapies to battle ageing. The self-treatment, which has been ongoing for the past six months, has been met with a mixture of praise and criticism for a lack of scientific rigour

WHAT ARE TELOMERES? Telomeres are the protective caps on the ends of the strands of DNA called chromosomes, which house our genomes. In young humans, telomeres are about 8,000-10,000 nucleotides long. They shorten with each cell division, however, and when they reach a critical length the cell stops dividing or dies. This internal 'clock' makes it difficult to keep most cells growing in a laboratory for more than a few cell doublings. Previous research has found telomere length can reliably predict life expectancy in humans. Advertisement

The self-treatment, which has been ongoing for the past six months, has been met with a mixture of praise for innovation and criticism for a lack of scientific rigour.

But now, Parrish claims to have become the first human being to be successfully rejuvenated by reversing 20 years of normal telomere shortening.

Telomeres are short segments of DNA which cap the ends of every chromosome, acting as 'buffers' against wear and tear.

They shorten with every cell division, eventually getting too short to protect the chromosome, causing the cell to malfunction and the body to age.

In September 2015, 44 year-old Parrish received two of her own company's experimental gene therapies.

The first one was to protect against loss of muscle mass with age, and the second was to battle stem cell depletion responsible for diverse age-related diseases and infirmities.

In one treatment, she received injections into her muscles containing the gene follistatin, according to MIT.

In animal experiments, this has been shown to increase muscle mass by blocking myostatin, which inhibits muscle growth.

She says she also received an dose of viruses containing genetic material to produce telomerase, a protein that extends telomeres.

The procedures were done in Colombia, to get around US regulations.

The treatments was originally intended to demonstrate the safety of the latest generation of the therapies.

But if early data is accurate, it is the world's first successful example of telomere lengthening via gene therapy in a human individual.

Gene therapy has been used to lengthen telomeres before in cultured cells and in mice, but never in a human patient.

Telomeres are the protective caps (shown in green) on the ends of the strands of DNA called chromosomes, which house our genomes. In young humans, telomeres are about 8,000-10,000 nucleotides long. They shorten with each cell division, however, and when they reach a critical length the cell stops dividing or dies

In September 2015, telomere data taken from Parrish's white blood cells by SpectraCell's specialised clinical testing laboratory in Houston, Texas.

It immediately before therapies were administered, revealed that Parrish's telomeres were unusually short for her age, leaving her vulnerable to age-associated diseases earlier in life.

In March 2016, the same tests were taken again by SpectraCell revealed that her telomeres had lengthened by approximately 20 years, from 6.71kb to 7.33kb.

HOW TELOMERES ARE SHORTENED Last year, scientists at Stanford University described their method of lengthening telomeres by using modified messenger RNA. RNA carries instructions from genes in the DNA to the cell's protein-making factories. The RNA used in this experiment contained the coding sequence for TERT - the active component of a naturally occurring enzyme called telomerase. When the cells are treated, they behave as if they are younger and multiply quickly rather than dying. 'One day it may be possible to target muscle stem cells in a patient with Duchenne muscular dystrophy, for example, to extend their telomeres,' said Dr Blau. 'There are also implications for treating conditions of aging, such as diabetes and heart disease. 'This has really opened the doors to consider all types of potential uses of this therapy.' The researchers also hope that the method will be able to allow scientists to generate large numbers of cells that could someday lead to an effective anti-aging drug. Advertisement

This implies that Parrish's white blood cells (leukocytes) have become biologically younger.

These findings were independently verified by the Brussels-based non-profit HEALES (HEalthy Life Extension Company), and the Biogerontology Research Foundation, a UK-based charity committed to combating age-related diseases.

'Current therapeutics offer only marginal benefits for people suffering from diseases of aging,' said Parrish.

'Additionally, lifestyle modification has limited impact for treating these diseases.

'Advances in biotechnology is the best solution, and if these results are anywhere near accurate, we've made history', Parrish said.

Parrish's statement has led to one member of her company's scientific advisory board distancing himself from the firm, according to MIT Technology Review.

This is a big problem,' says George Martin, a professor at the University of Washington and the former scientific director of the American Federation of Aging Research.

MIT says he'd agreed to advise Parrish several months ago but resigned his role recently.

'I am very upset by what is happening. I would urge lots of preclinical studies,' he says.

Meanwhile, BioViva will be testing new gene therapies and combination gene therapies to restore age related damage.

It remains to be seen whether the claimed success in leukocytes can expanded to other tissues and organs, and repeated in future patients.

For now all the answers lie in the cells of Elizabeth Parrish, 'patient zero' of restorative gene therapy.

Far more data is needed before claiming success against aging, Dana Glei, a senior research investigator at Georgetown University said.