Stem cells are cells with incredible properties that set them apart from other types of cells. They are early stage cells that can remain and duplicate as stem cells, or they can transform into any other type of cell as they develop. For instance, a stem cell can become a lung cell, heart cell or even a brain cell.
Stem cells basically function in two different ways. Most commonly they function as undifferentiated cells (meaning they can become other types of cells) through a process of cell division. They can also be induced to become a specific type of cell through conditions like experimentation.
That’s a key reason why they have become such a significant breakthrough in modern medicine.
But let’s step in just a bit deeper and delve into the more technical aspect of stem cells…
Multi-celled organisms like plants and human beings are classified as eukaryotes. A single-celled organism, like bacteria, is classified as prokaryote.
A eukaryote originates from a single stem cell that differentiates into a multi-celled organism like a plant or a human being. The sperm of man fertilizes the egg of the woman in the womb. The fertilized egg results in a zygote.
The zygote is composed of one stem cell. The reason is that the zygote contains 46 chromosomes, the number of chromosomes that make a human being. The father contributes 23 chromosomes via the sperm; the mother contributes 23 chromosomes via the egg. Differentiation is demonstrated by fetal development. Let’s trace the path of differentiation. This zygote differentiates and results in an embryo, which differentiates into a fetus, which it turn differentiates into a full term which is ultimately delivered as a baby.
What happens during differentiation is very technical or it involves a language that is very scientific. However for now, let’s just focus on descriptions and results of differentiation at different stages.
There are stages of differentiation. The zygote is in the stage of totipotent stem cell. Totipotent stem cell differentiates into pluripotent stem cell. Pluripotent stem cell differentiates into multipotent stem cell. Multipotent stem cells can differentiate into unipotent stems cells that can differentiate into adult stem cells.
A pluripotent stem cell can differentiate into tissues like endoderm, mesoderm, and ectoderm. The endoderm makes up the” innermost layer of the embryo” (Bellomo, M. The Stem Cell Divide. 2006:36). The mesoderm, also called middle layer, develops into blood, bone, muscle, and marrow.
Stem cells in a particular stage multiply themselves by means of cell division, also called mitosis. One stem cell duplicates itself resulting into two daughter stem cells, that divide into four daughter stem cells, that divide into 16 daughter stem cells, and so forth and so on. In each stem cell there is a growth factor that triggers mitosis. Likewise, each stem cell has a regulatory factor that limits the size, structure and shape of tissue.
Assumption of design
There is an assumption that stem cells differentiate to fulfill a design for an organism like a plant or a human being. That is why a person will not grow into the size of an elephant, or a lemon grass will not grow into the size of a bamboo.
Some stem cells in each stage of differentiation stay in reserve, while others go on to differentiate into the next stage. This fact has an implication in the treatment of diseases and healing. Stem cells in each stage can be damaged such that reserves are not enough to produce the amount of stem cells needed for replacement of sloughed off and worn out adult stem cells.
There are about 3 trillon cells of the human body (Human Genome Project. Internet. Sept. 30,2013). Some of them have definite lifespan, others are irreplaceable or hard to replace. For example, blood cells have a lifespan of 140 days. After this period a blood cell undergoes a natural death called apoptosis. Brain cell, nerve cells, and cardiovascular cells do not replace themselves.
Reserve stem cells are needed to produce replacements for apoptosed cells.
Adult stem cells are in varying levels of multipotency and unipotency.
They can develop into:
1. Brain cells, 2. Bone morrow cells, 3. Digestive system cells, 4. Endothelium, cells (found in the lining of arteries and veins), 5. Skin cells, 6. Skeletal muscle cells, 7. Pancreas cells, 8. Liver cells.
The natural course of differentiation is from totipotent stem cell to pluripotent stem cell to multipotent stem cell to unipotent stem cell to adult stem cell. That is, differentiation does not naturally take the reverse course of, say, from adult stem cell to totipotent stem cell.
[However, advancements in stem cell research have shown that this natural course can be reversed artificially. This will be discussed in another article. This has an implication on the development of stem cell therapy for use in treating diseases and healing.]
Only the union of the sperm and egg can create one stem cell – totipotent stem cell – that differentiates into a new human being. (We will have another article to discuss the development of plants.)
Stem cell research has shown that adult stem cells can be reprogrammed into pluripotent stem cells. This fact has a tremendous impact on treatment of diseases and healing by means of stem cell therapy. This fact also opens the door for stem cell supplements.