Professor Sir Doug Turnbull, a researcher of mitochondrial disease at Newcastle University who has pioneered MRT, said: 'This is obviously great news and I agree with the report conclusions. This gives women who have mitochondrial DNA (mtDNA) mutations reproductive choice, and I am delighted for them.'
The report concluded that 'it is appropriate to offer mitochondrial donation techniques as clinical risk reduction treatment for carefully selected patients'. MRT was legalised in the UK in 2015 (see BioNews 826), but with the provision that HFEA must find it safe before granting any licences, which led to the commission of this report.
MRT involves removing the nucleus from an egg cell of the mother and transferring it to a donor egg with healthy mitochondria, from which the nucleus has already been removed. This donor egg, containing genetic material from two women, is then fertilised using the father's sperm, resulting in a so-called 'three-parent embryo'.
The HFEA will decide at a meeting on 15 December whether to allow clinical trials of the therapy. If they decide in favour of mitochondrial donation, then the first procedures may be carried out in March or April 2017, according to an HFEA spokesman. The Newcastle Fertility Centre have already selected patients they believe to be suitable and are waiting to apply for a licence to carry out the procedure.
However, a paper published last week has reinforced concerns that the technique may not always prevent mitochondrial disease. Professor Shoukrat Milatipov and colleagues at the Oregon Health and Science University created embryos using MRT and tested their levels of donor versus defective mitochondria. The embryos themselves were virtually free of any defective mitochondria but, in some embryonic stem cell lines made from the embryos, the original defective mitochondria came back. This raises concerns that children born through MRT could develop mitochondrial diseases later in life.
'We know that the technique [of MRT] is currently imperfect,' said Dr David J Clancy, a mitochondrial researcher at Lancaster University. '[These] results suggest that reversion to the original mtDNA type could occur as often as one in six times. What proportion of children who inherit mitochondrial disease as a result of the therapy is considered a safe number?'
Mitochondrial donation has been developed as a technique to help women with mitochondrial diseases conceive healthy babies – mitochondria are solely inherited from the mother, so women who have mitochondrial diseases will pass them directly to their children. Mitochondrial diseases include a wide variety of conditions such as Leigh's syndrome and MELAS syndrome, and they can be fatal. Around one in 10,000 births have some form of mitochondrial disease.