If you’ve ever looked up human embryonic stem cells (hESCs) in technical journals or textbooks, you have probably seen them defined as pluripotent cells derived from the inner cell mass of a 5 – 8 day old preimplantation blastocyst. In plain english, this means that human embryonic stem cells are immensely powerful and versatile cells that are carefully isolated from the interior of a fertilized egg, 5 to 8 days after fertilization and before said fertilized egg has had a chance to attach itself to the thickened walls of the uterus. The last part of the statement above is a bit misleading because it’s not like scientists are on constant standby ready to accost people and take their fertilized eggs from them after sexual intercourse. Rather, most human embryonic stem cells are derived from eggs that were fertilized using IVF (in vitro fertilization) techniques. First off, you are probably wondering what the heck “in vitro” means. Well “in vitro” is latin for “in glass” and back in the day, laboratory utensils and equipment were made of glass so in vitro fertilization of a human egg simply means the human egg was fertilized in a laboratory dish rather than in the fallopian tubes of a woman. And yes, you read that correctly… modern science has endowed us with the power to fertilize a human egg right in a laboratory dish provided that the right temperature and chemical conditions are present. These IVF derived embryos are then grown in a laboratory as they go through the multiple cellular divisions that would usually result in the formation of a full human being if it occurred in the womb. After 5 – 8 days of development, the fertilized egg takes the form depicted in the figure below due to multiple cell divisions and physical cell movements. At this stage, the fertilized egg or embryo is called a blastocyst and the tiny clump of cells within its fluid filled cavity is called the ICM or inner cell mass. This tiny clump of cells that we call the inner cell mass will eventually give rise to a full blown human being if normal development is allowed to occur in the womb. The inner cell mass is the source of the super versatile and powerful embryonic stem cells that you have probably heard about in popular scientific culture. Continue reading Stem cells, artificial organs, and the potential for a healthier future
