Christian Worldview Concepts

The Promise and Peril of the Embryo

The Science (or Science Fiction) of Stem Cell Research

With only a few exceptions, every cell in the body contains the complete genetic code established at conception. In biological terms, the genetic makeup of every cell is identical to that of every other cell in that individual. The key question is how do the cells become different types of tissue but still possess the exact same DNA? How can the same DNA be expressed differently in the two-hundred or more tissue types that make up the human body?

Developmental biologists tell us that this work is done by stem cells, which have two important properties. First, they have the capacity to divide for indefinite periods of time and, secondly, they have the ability at each cell division to give rise both to a similar stem cell as well as a more specialized cell type¹. This means that they not only produce cells for a specific tissue type, they also produce additional stem cells, which means that the population of stem cells is relatively constant so that more specialized stem cells can be made².

Biologically speaking, human embryos are stem cell factories. The first eight cells of the embryo are called totipotent stem cells, a term which means that these cells can become any one of the 200 tissue types found in human beings. Without becoming too technical, once the embryo reaches a certain stage of development, the stem cells are believed to cease being totipotential and become what is called pluripotential, meaning that they are much more limited in the kinds of tissues they can become. Cell specification at this point restricts a stem cell from becoming just any type of tissue.

It is the embryo at the trophoblast stage that excites many researchers the most because it is believed that the trophoblast retains totipotent properties, that is, it can potentially become any tissue type. Researchers believe that if they can find out what makes these cells become specific tissue types, they may be able to find ways to use them in treating diseases such as cancer, Alzheimers, Parkinsons, diabetes, heart disease and a host of other ailments.

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¹ Gilbert, S.F., Tyler, A.L., et al., Bioethics and the New Embryology: Springboards for Debate (Sunderland, MA: Sinauer Associates, 2005), p. 143
² Gilbert, p. 143