Human embryonic and adult stem cells have different abilities in terms of the number of cell types they can differentiate into. Embryonic stem cells can give rise to most of the body cells, and are pluripotent, while adult stem cells have limited potency and differentiate into cell types of their tissue of origin.
Embryonic stem cells can be grown and harvested easily in culture with a well controlled environment, but adult stem cells are rare in mature tissues. Therefore, isolation is rather difficult. Methods for culturing of adult stem cells are not well developed. This may slow down the development of the usage of adult stem cells in cell replacement therapies, as large quantities of cells are required.
The tissues derived from embryonic and adult stem cells may differ with regard to immune rejection after transplantation. There is only limited information available for embryonic stem cell transplantation, as the first phase clinical trial testing the safety of cells derived from embryonic stem cells was only approved in the US in 2009. There is the possibility of rejection due to the difference of genetic makeup of the embryonic stem cells and the recipient. For adult stem cells, there is less likely to be a rejection after transplantation, as scientists are able to culture the patient's own cells and differentiate them into specific cell types. This can minimize the immune response for rejection of the transplanted tissue. This is an important consideration before any transplantation, as rejection can aggravate the situation and continuous administration of immunosuppressive drugs causes many side effects.
The animation in Activity 4 gives a comprehensive picture of stem cell biology on the embryonic and adult stem cells. It also discusses two examples of haematopoietic and intestinal stem cell. Finally, the animation introduces the techniques of culturing and controlling stem cell growth under in vitro conditions, and the potential therapeutic values of stem cell research.
Embryonic and adult stem cells are the two major types of stem cell. There are other stem cell types found to be useful, such as cord blood stem cells. Stem cell therapy is also being extensively studied in the medical field. These are the current and potential areas of research, which we will discuss in the next section.
To round off this section on the types of stem cells in humans, attempt Self-test 3.
- Why can't adult stem cells substitute for the use of human embryonic stem cells in research?
Activity 3 feedback
Human embryonic stem cells have greater developmental potential than adult stem cells. They can give rise to almost all cell types of the human body, and are pluripotent. However, the adult stem cell is multipotent, and is restricted to a specific subpopulation of cell types.
Watch the following animation.
Then answer the following questions.
- What are the functions of CDX2 and Oct-3/4 in a blastocyst?
- What are three tissues or systems with poor regeneration power after injuries or degenerative diseases?
Activity 4 feedback
- CDX2 is the gene that controls early embryogenesis, which is required to form the placenta. Oct-3/4 gene expression facilitates the formation of the inner cell mass, maintains pluripotency and differentiates into trophectoderms.
- The nervous system, the heart and the pancreas.
- There are two main types of stem cells the body. Name these two kinds and explain their function.
- Summarize the different characteristics of embryonic and adult stem cells in the following table.
|Embryonic stem cells||Adult stem cells|
- What are the roles of stem cells in the body?
- We are not sure what roles stem cell play in the body.
- They produce new specialized cells to replace dead or used cells.
- They can produce insulin.
- They fight against infections.
Self-test 3 feedback
- Embryonic stem cells are harvested from the blastocyst of a four to five day old human embryo. An embryonic stem cell consists of an inner cell mass (ICM, embryoblast) and an outer cell mass (trophoblast), forming the embryo and placenta respectively after implantation to the uterus. Adult or somatic stem cells exist in the body after embryonic development, to maintain and repair the tissue where they are found.
- Different characteristics of embryonic and adult stem cells
|Embryonic stem cells||Adult stem cells|
|Cell culture||Embryonic stem cells can be grown and harvested easily in culture with a well controlled environment.||The culturing methods of adult stem cells are not well developed.|
|Transplantation, rejection||There is a possibily of rejection due to the difference in the genetic makeup of the embryo stem cells and the recipient.||Rejection is less likely: patient's own cell is cultured and differentiated into specific cell types. Rejection still occurs if the genetic makeup of donor cells is different from recipient cells.|
- B. We understand the roles of stem cells in this unit. Scientists have revealed the function of stem cells extensively (Not A). Cells in the pancreas produce insulin (Not C). White blood cells fight against infection (Not D).