Human embryonic stem cells (hESCs) have many remarkable properties, not the least of which is their ability to turn into every other kind of cell in our body. But there are limits to what researchers can do with embryonic stem cells. One issue is that there aren’t always hESCs available – they come from eggs donated by couples who have undergone in vitro fertilization. Another is that researchers can only develop these cells in the laboratory for 14 days (though that rule may be changing).
Now researchers at Caltech have developed a kind of hESC-in-a-dish that could help make it easier to answer questions about human development without the need to wait for a new line of hESCs.
The team, led by Magdalena Zernicka-Goetz, used a line of expanded pluripotent cells (EPSCs), originally derived from a human embryo, to create a kind of 3D model that mimics some of the activities of an embryo.
The cool thing about these cells is that, because they were originally derived from an embryo, they retain some “memory” of how they are supposed to work. In a news release Zernicka-Goetz says this enables them to display elements of both polarization and cavitation, early crucial phases in the development of a human embryo.
“The ability to assemble the basic structure of the embryo seems to be a built-in property of these earliest embryonic cells that they are simply unable to ‘forget.’ Nevertheless, either their memory is not absolutely precise or we don’t yet have the best method of helping the cells recover their memories. We still have further work to do before we can get human stem cells to achieve the developmental accuracy that is possible with their equivalent mouse stem cell counterparts.”
Being able to create these embryo-like elements means researchers can generate cells in large numbers and won’t be so dependent on donated embryos.
In the study, published in the journal Nature Communications, the researchers say this could help them develop a deeper understanding of embryonic development.
“Understanding human development is of fundamental biological and clinical importance. Despite its significance, mechanisms behind human embryogenesis remain largely unknown…. this stem cell platform provides insights into the design of stem cell models of embryogenesis.
The Stem Cellar 
Most pregnant women experience sudden and dramatic increase in estrogen and progesterone. Both estrogen and progesterone play major roles to maintain well being of pregnancy women. Estrogen has critical roles to maintain health of pregnant women, fetus development and maturation. Whereas, progesterone stimulates thickening of uterine lining for implantation of fertilized egg and transforming uterus from small size of pear into uterus can accommodate a full term baby. Several other hormones have been identified during pregnancy. These are: 1)Human chorionic gonadotropin hormone stimulate ovaries to produce estrogen and progesterone continuously during development of the embryo. 2)Human placental lastogen also known as human chorionic somatomammotropin has role to provide nutrition to the fetus. Thus, ovary and placental produce several hormones to maintain the health of pregnant women. Evidence showed that estrogen levels increase steadily during pregnancy and reach peak in their trimester. However, progesterone is extraordinary high during pregnancy to maintain the well being of pregnant women and fetus. The changes in the level of hormones have greater impact on growth factors production during development of fetus. The embryo requires growth factors to support the formation of internal organs, external structures, elongation of neural tube, vascularization and brain development.
The process of embyogenesis in human embryo requires growth factors to develop into different parts of tissues and organs. Embryo in vivo depends on placental to provide a variety of growth factors to support fetus growth and differentiation. This is not seen in in vitro model, the limited supply of growth factors causes defect in tissues and organs development. Evidence showed that maturation of embryo stem cells requires many stages of growth and differentiation to produce mature and functioning cells. Each stage of maturation, the progenitors respond to different growth factors and turn on the specific gene for expression. Lack of specific growth factor in anyone stage of maturation may result in prematurely development of tissues and organs. Thus, human placental becomes a focus of extensive investigation to determine specific growth factors regulate each stage of fetus development.