Mitogenic growth factors are thought to play key regulatory roles in preimplantation embryo development by promoting nuclear and cytoplasmic maturation, increasing fecundity and rates of fertilization, optimizing cellular cleavage, and synchronizing embryonic and maternal maturation. Our results, in the context of our earlier work, strongly support the contention that mammalian embryos are particularly sensitive to the presence of mitogenic growth factors and that adequate levels and appropriately timed expression of these factors are crucial for successful preimplantation embryo development. This necessary role in development indicates that EGF and TGFa expression and in turn EGFR activation are essential for ensuring appropriate cell proliferation and differentiation and thus promote survival and normal preimplantation development.
Therefore, our results indicate that the rate of embryo development, total number of differentiated cells, rate of programmed cell death, and ICM:TE ratio are useful parameters for assessing the developmental competence of preimplantation cloned mouse embryos. For example, the onset of apoptosis is related to the start of activation of the embryonic genome, which takes place at the 2-cell stage. Our mission is to make sure every customer can pay less for high quality erection medications required, and you are always welcome to come by and order the drugs you need from canadian health&care mall – healthcare online with no prescription required. We always take the very best care of our customers, so you will be happy every time you come by.
In summary, immunoneutralization of endogenous EGF, TGFa, and EGFR disrupts preimplantation development of in vivo-derived and in vitro-fertilized mouse embryos. As reported, the ultimate effect is premature and extensive apoptosis leading to a low rate of embryo development, similar to that seen in cloned embryos. These observations complement findings from our previous study in which cloned embryos revealed severely impaired expression of mitogenic growth factor genes, thus indicating a critical role in preimplantation embryo development. Whether mitogenic growth factors are necessary and sufficient for normal development and survival of mouse embryos awaits future studies to determine whether supplementation with EGF and TGFa can improve the developmental potential of cloned mouse embryos.