New hope for mitochondrial disease sufferers

By Helen Albert, Senior medwireNews Reporter

medwireNews: Scientists have succeeded in replacing mitochondrial (mt) DNA in human oocytes, which they hope will lead to the procedure being developed for use in patients with mitochondrial diseases.

"The goal of this research is to develop a therapy to prevent transmission of these disease-causing gene mutations," said investigator Shoukhrat Mitalipov (Oregon Health and Science University, Portland, USA) in a press statement.

As reported in Nature, Mitalipov and colleagues managed to fertilize 73% of 65 donated oocytes that had undergone mtDNA transfer, known as spindle-chromosomal complex transfer (ST), although 52% of the ST oocytes showed signs of abnormal fertilization determined by having an abnormal number of pronuclei.

Of the ST oocytes that were fertilized normally, blastocyst development and embryonic stem cell isolation occurred in 62% and 38%, respectively; rates that were comparable to those of normal oocyte controls (n=33).

The team derived cell lines from the ST oocytes and found that all cells had normal euploid karyotypes and only contained donor mtDNA.

Mitalipov and co-investigators hope that their discovery could lead to the development of treatments for people with mitochondrial disorders, although they emphasize that the work is at an early stage and that further work in nonhuman primates is needed to optimize the protocols used and ensure that the procedure can be carried out safely.

"Using this process, we have shown that mutated DNA from the mitochondria can be replaced with healthy copies in human cells," explained Mitalipov.

"While the human cells in our study have only allowed us to develop to the embryonic stem cell stage, this research shows that this gene therapy method may well be a viable alternative for preventing devastating diseases passed from mother to infant."

The researchers say that the US Food and Drug Administration should review these developments, emphasizing that at present funding restrictions will need to be amended before any federally funded clinical trials can be undertaken.

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