ES cells. Where do they come from? Part One.
Disclaimer: This is not a religious blog, but a scientific one (kinda). That said, the facts presented below are not intended to ruffle any feathers, but to simply outline the biological aspects of a population of stem cells. What I present below is the result of decades of rigorous scientific research, medical knowledge, and peer review. It has been repeated many times over by researchers all over the world, and validated to be deemed correct, and the baseline for much of the science behind the field of regenerative medicine.
Perhaps one of the most egregious accusations made toward stem cell researchers is the notion that we take the life of babies to make these cells. Though based largely on ignorance, one thing is true: Once the ES cells are isolated, the embryo is no longer viable. But is it a baby? Medically, biologically, developmentally, and categorically…..NO…..Not even close.
Embryonic stem cells are isolated from the pre-implantation blastocyst stage embryo, typically about 4 to 5 days post fertilization (you know, the fun part). This is the stage of embryo that has not attached to the uterine lining and still runs a very real risk of being flushed out by the body, which is very common. On a cellular level, the embryo consists of the outer trophecteoderm layer which will contribute to the placental tissue, a fluid-filled cavity called the blastocoel, and the inner cell mass, or ICM. It’s the ICM which contributes to the embryo itself. There is no beating heart, no limb buds, no centralized nervous tissue. There isn’t even a physical connection to the uterine lining. Therefore, this is not a baby. I have a baby at home. Looks nothing like an ICM, though if you saw him, you might argue that he is indeed gaining cell mass at a stupefying rate.
Moving on… At this stage, this ICM is a tightly packed mass of cells that have no specialization at all and are the cells that are harvested to make ES cells. Once isolated from the trophectoderm, these cells can be expanded in culture and can be tweaked to generate all the different cell types of the body. This is what most people think of when they think of the term “ES cell.”
Here’s a question I get a lot: “OK fine. But who’s donating their embryos for this?’
Currently, there are essentially 3 sources of human ES cells:
1- Existing human ES cell lines
2- Made-to-order lines made via the same approach used to create Dolly the sheep (remember her?)
3- In vitro fertilization clinics
So, we have options, which is nice. Although it may seem like there is a huge ethical conundrum with the above options, a little insight may help to alleviate some concern. But that’s next week’s blog, dear scientist. In the meantime, be extra careful with your cells. It’s summertime and fungal contamination has been known to hide in air condition vents and other fun places. No sense in losing valuable research time before the students come back in the fall!