Genetic technologies invade every aspect of medicine. Here we find another example of a technology that could significantly assist us in identifying the embryo that will make a baby.
The authors suggest measuring telomere length may be a measure of embryo health. If so, then this test may be a very valuable tool to access many aspects of embryology and clinical IVF.
Telomere lengths in human oocytes, cleavage stage embryos and blastocysts
Turner S, Wong HP, Rai J, Hartshorne GM. Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, Clifford Bridge Road, Coventry, CV2 2DX, UK.
- Telomeres are repeated sequences that protect the ends of chromosomes and harbour DNA-repair proteins.
- Telomeres shorten during each cell division in the absence of telomerase.
- When telomere length becomes critically short, cell senescence occurs.
- Telomere length therefore reflects both cellular ageing and capacity for division.
We have measured telomere length in human germinal vesicle (GV) oocytes and pre-implantation embryos, by quantitative fluorescence in-situ hybridisation (Q-FISH), providing baseline data towards our hypothesis that telomere length is a marker of embryo quality.
The numbers of fluorescent foci suggest that extensive clustering of telomeres occurs in mature GV stage oocytes, and in pre-implantation embryos.
When calculating average telomere length by assuming that each signal presents one telomere,
- the calculated telomere length decreased from the oocyte to the cleavage stages, and
- increased between the cleavage stages and the blastocyst (11.12 vs 8.43 vs 12.22kb respectively, p<0.001).
Other methods of calculation, based upon expected maximum and minimum numbers of telomeres, confirm that telomere length in blastocysts is significantly longer than cleavage stages.
Individual blastomeres within an embryo showed substantial variation in calculated average telomere length. This study implies that telomere length changes according to the stage of pre-implantation embryo development.