Scientists at the university of Cambridge UK and US (Prof. Brivanlou at the Rockefeller University, New York) have developed a remarkable new technique that allows human embryos to grow in the lab-beyond the implantation stage.
So far, an embryo had to implant in the uterus by day 7 to survive, but it is impossible to see what is happening inside the maternal environment at this stage regarding all the complex cellular and molecular events taking place.
Crucially, it is during that period that 2/3 of pregnancies fail, because embryo does not impant properly. Following fertilization, a zygote develops into a blastocyst with two cell lineages: the tromphectoderm and the inner cell mass. Within the reproductive tract, the blastocyst is guided down the fallopian tube and starts to impant into the uterus around day 7. The uterus is only receptive for a short time and the molecular basis - apparently relying on maternal tissues and hormone signals - for this permissive window is poorly understood.
The exploration of the process of implantation is also of major importance since it is from this stage onwards that the embryo really begins to take shape and at which many developmental defects can become acquired. This research, published in Nature and Nature all Biology, however, chemically mimics the maternal layer of the uterine cells with a 3D matrix and discovered that immediately after the implantation that comprise the blastocyst reorganize into a new formation. This reorganization process occuring through cell-cell interactions rather than through programmed cell death as previously thought was similar to the observed in mouce embryos but with significant differences regarding the genes expressed and the structure.
Undoubtedly, this technique, on the one side, promises new insights aiming at helping impove the chances of IVF success by determining the causes of miscarriages and infertility. It will also assist in the rational design of differentiation protocols of human embryogenic stem cells to specific cell types for disease remodelling and all replacement therapy.
However, on the other side, the ability to grow a human embryo in vitro for 13 days raises ethical and policy considerations. In the UK and in at least 12 other countries experiments on human embryos older than 14 days are not allowed. However, in December last year a new proposal to extend the limit from 14 days was submitted to the House of Common Science and Technology Committee in the UK.
Source: Bionews (9 May 2010) (16 May 2016)
The Guardian
Paraskevi Sisi Bsc, PhD
Senior Clinical Embryologist
Embryogenesis