What is Regenerative Medicine and Stem Cells?

 

Regenerative medicine is a unique medical field that combines many different fields in medicine for the purpose to repair or restore the tissue function damaged by disease.  Regenerative medicine is distinct from conventional treatment approaches that only treats disease symptoms or slows the progression of disease. Regenerative medicine treatments typically fall into four categories:  

 

a. Growing organs or tissues in a laboratory and transplanting them when a vital organ is dying.

b. Growing large number of stem cells under artificial conditions and then delivery those cells to a diseased organ.

c. Synthesizing a unique protein that activates a specific biological pathway that is important in tissue regeneration.

d. Synthesizing a small molecule or chemical that activates a specific biological pathway that repairs a diseased organ.

 

In each of the above cases, a patient's own stem cell can serve as a source to produce all the above solutions.  However, not all stem cells are equal.  There are a variety of stem cells.  Adult stem cells refer to stem cells that arise from the moment of birth and persist through adulthood.  Embryonic stem cells and fetal stem cells represent controversial stem cells that are derived from a destroyed embryo and fetus respectively (1,2).

 

There are several adult stem cells that are derived from newborn tissues (umbilical cord blood, umbilical cord and placenta). Adult stem cells also are derived from bone marrow and from fat tissue which are also readily available.  Many organs possess a small resident of adult stem cells but are problematic or unethical to extract such as heart, brain and liver.

 

These aforementioned adult stem cells are also called somatic stem cells.  Somatic stem cells pose advantages and disadvantages. Somatic stem cells exhibit genetic stability and do not form tumors when transplanted into patients.  However, somatic stem cells have restricted diversity and can only form limited types of tissue (2).  For example, hematopoietic stem cells can only repopulate blood cells. Another common stem cell called mesenchymal stem cells (derived from bone marrow and fat for example) can produce connective tissues such as bone, cartilage and fat.

 

Somatic stem cells also have defined growth capacity. Stem cells typically represent a small number of cells from a tissue and must be purified and grown artificially to a high enough dose for treatment. Depending on the type of treatment and specific organ that is treated, the growth capacity of that stem cell may not be sufficient to treat that disease.

 

Another class of stem is called a pluripotent stem cells which exhibit the most diversity and growth potential (1,2,3). Pluripotent stem cells can produce all the tissues of the body.  There are 2 types of pluripotent stem cells:

 

1. Embryonic and fetal stem cells.

2. Induced pluripotent stem cells.

 

Embryonic stem cells and fetal pluripotent stem cells represent ethically controversial stem cells.  Induced pluripotent stem cells are described elsewhere.  Pluripotent stem cells exhibit genetic instability and form tumors when injected into experimental animals.

 

References:

 

(1) Science. 1998 Nov 6;282(5391):1145-7.

 

(2) Neurodegener Dis Manag. 2014;4(4):297-307.

 

(3) Cell. 2007;131(5):861-72.