![]() Both these embryos with two ICMs hatched completely.? Ms Payne said: ?The second ICM was evident early in blastocyst formation in both embryos, and appeared to be the result of some ICM cells relocating and adhering to the opposite trophectoderm wall, seeded during an early collapse of the blastocyst. The most common form of monozygotic twinning (identical twins resulting from the dividing of one embryo fertilised by a single sperm) is monochorionic/diamniotic, when two ICMs form before hatching. However, two of the 26 embryos (8%) had two distinct ICMs and a third had a possible second ICM. There was no evidence of embryo splitting during the hatching ? which was one of the theories as to how twins were formed from a single blastocyst. ![]() Seventeen of the 33 embryos went on to become fully formed blastocysts and 11 either started to hatch or hatched completely from the zona pellucida (the gelatinous protective coating around the blastocyst).įifteen embryos degenerated during culture and 11 of them did not re-expand after a collapse and subsequently degenerated. In some cases the embryo cannot re-establish the junctions and the blastocyst is unable to re-expand and thus dies.? The greater the number of failed junctions, the more severe the collapse. The magnitude of the collapses is determined by the number of failed junctions. These collapses occur quite quickly ? far more quickly than a pump could manage. I believe that the collapses occur when some of the junctions between the cells fail ? possibly due to localised cell death, or maybe due to a structural weakness in the junction itself ? and the blastocoelic fluid leaks out. ![]() The trophectoderm maintains the pressure by pumping the fluid into the cavity. ?The fluid in the cavity must be under positive pressure as this pressure is the motive force for expansion of the blastocyst. She explained the mechanism that underlies blastocoelic collapse and re-expansion. ?The frequency and degree of collapse varied, but the embryos that died tended to be those that had bigger and more frequent collapses,? said Ms Payne. ![]() The time-lapse recording showed that at this stage the blastocoele collapsed at least once in 25 of the 26 embryos (96%). These outer cells (the trophectoderm) begin to pump fluid into the blastocoelic cavity where a micro-environment is formed in which the cells that will go on to develop into the body of the embryo (the inner cell mass or ICM) develop. This is a fluid-filled cavity in the blastocyst and is formed on about day four or five when the embryo forms tight junctions between the cells around its periphery. They then used the software to analyse data from the film.Īfter thawing, 26 of the 33 embryos (most of which were composed of between two and ten cells) developed to blastocyst stage in which the blastocoele is formed. Using 33 surplus frozen-thawed embryos that had been donated for research, Ms Payne and her colleagues used computer software called MetaMorph, which creates a free-running film from single images taken every two minutes with a digital camera attached to a microscope. However, it was not known why this happened. Furthermore, the research has shown that the culture in which the IVF embryos are formed is possibly responsible for the embryos dividing into twins.ĭianna Payne, a visiting research fellow at the Mio Fertility Clinic, Yonago, Japan, told the 23rd annual meeting of the European Society of Human Reproduction and Embryology today (Monday 2 July) that about three pairs of twins per thousand deliveries occurred as a result of natural conception, but many more were born after IVF, even when only one embryo had been transferred to the mother (approximately 21 pairs per thousand deliveries). Evidence gathered from time-lapse recordings of the formation of early embryos (blastocysts) in the laboratory has revealed why embryos created via IVF and undergoing extended culture are more likely to develop into twins than those created via natural conception.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |