All About Stem Cells: Different Types & Sources Of Stem Cells

You've probably heard about stem cells on science blogs, newspaper articles, or even on social media! You must also be aware of the claims that stem cells are "miracle cells," "life-giving," and even capable of curing cancer. Well, you heard it right. Stem cells are capable of doing all that but how do they function? Well, it all comes down to the various sources of stem cells. The characteristics of stem cells usually vary depending on the source from which they're extracted. So are you ready to learn about stem cells, their classifications and applications? Let’s start with the definition of stem cells!

The term stem cells was first coined by William Sedgwick in 1886, to define the “regenerative quality” of  plants. ¹ They’re defined as multipotent cells that can differentiate into muscle cells, red blood cells, brain cells, heart muscle cells, and bone cells. ²  

Let’s take a look at the different categorization of stem cells in the following section:

Categorization Based On Sources Of Stem Cells

Depending on the sources of stem cells, they are divided into the following types:

Embryonic stem cells

Stem cells that are retrieved from human embryos are about 4-7 days old, post-fertilization. Naturally, these cells are pluripotent (have the ability to develop into any kind of cells and tissues). Embryonic stem cells are harvested via in-vitro fertilization, due to ethical reasons. ^{5, 6}

In addition to being pluripotent, these cells have other special properties, such as self-renewal, structural repair and growth, and rapid cell division. Clinical applications of embryonic stem cells (developed from iPSCs/ Adult stem cells) have shown therapeutic potential and are considered in the management of diabetes and cardiovascular diseases. ^{7, 8}

Researchers have discovered a way wherein adult human cells could be reprogrammed to mimic the qualities of embryonic stem cells, in the form of induced pluripotent stem cells (iPSCs). ⁹

Fetal stem cells

These stem cells are extracted from a fetus and can be harvested from an embryo after the 8th week. Fetal stem cells may be taken from the fetal blood, bone marrow, or other fetal tissues such as liver and kidneys. ¹⁰

In comparison to adult stem cells, fetal stem cells are known to have better intrinsic engraftment, greater multipotency, and lower immunogenicity. ¹¹ 

Adult stem cells

Adult stem cells (ASCs) are pluripotent cells that can regenerate, replacing the damaged or dead tissue. They can be found in some of the body's differentiating tissues. ¹² ASCs' primary job in our bodies is to constantly repair, regenerate, and replace the cells that need to be replenished. Only 3 types of cells—neural cells, mesenchymal stem cells, and hematopoietic stem cells—can develop from adult stem cells.¹³ 

Umbilical cord blood stem cells

These stem cells are retrieved from the umbilical cord blood (and placenta) of a newborn. ¹⁴ Umbilical cord blood contains hematopoietic stem cells that is used to treat numerous genetic diseases, cancers, as well as inherited disorders. ¹⁵ 

Categorization Based On Differentiation Potential

So far, we’ve discussed the categorization based on different sources of stem cells. Now, let’s take a look at how stem cells are categorized based on their differentiation potential. 

Totipotent stem cells

Totipotent stem cells have the ability to differentiate into any cell. The zygote formed during egg fertilization is among its best examples, because, it can grow into any type of cell, including the placental cell. ³ The only totipotent stem cells in the human body are those formed by embryonic cells following the first couple of cell divisions. ¹⁶

Pluripotent stem cells

Embryonic stem cells are considered pluripotent because they can differentiate into any type of cell, with the exception of placental cells. Furthermore, pluripotent stem cells are produced in the initial stages of embryonic stem cell differentiation. However they can also be derived from the germ layers (a group of cells found in embryo during its development) ¹⁷ , which include the mesoderm, ectoderm, and endoderm.^{18, 6,19}

Multipotent stem cells

Multipotent stem cells are present in almost all the tissues. MSCs or Mesenchymal stem cells are the most common example of multipotent stem cells. These stem cells can be extracted from adipose tissue, bone marrow, peripheral blood and even umbilical cord blood. ²⁰

Uses Of Stem Cells

After learning about the various types of stem cells, you might be curious about their applications. Here  we’ve enumerated few uses of stem cells (some of which are still in initial research stage):

• Stem cell transplants: This procedure  involves extracting healthy stem cells from blood/ bone marrow of an individual and transplanting them into another person (or patient who requires healthy  stem cells).²¹ Stem cell transplants are beneficial for treating various cancerous and non-cancerous diseases, such as acute leukemia, multiple myeloma, neuroblastoma and lymphoma.²²
• Drug testing: iPSCs (induced pluripotent stem cells) are stem cells which are grown in labs. iPSCs have huge potential in various medical research fields and are actively used in drug testing.²³ For instance, researches have successfully generated liver cells, using stem cell technology to test the action of drugs on liver.^24,25
• Disease modeling: In order to comprehend the causes of a disease, scientists frequently develop a disease model. This entails creating a biological system (using iPSCs) in the laboratory that closely resembles the disease or exhibits similar disease processes.^26,27  
• Regenerative medicine:  It’s a process  which deals with “replacement of damaged tissue or organs.”²⁸ The application of stem cells in regenerative medicine could be seen in the treatment of conditions such as heart failure, tooth regeneration, and wound healing.²⁹

Stem Cells: Paving A Way For Treatment Options

• As we’ve learned so far, stem cells have the ability to renew, regenerate, and differentiate into other cells. Stem cells can recreate functional tissues, and can perform tissue specific functions as well. ⁹ However, stem cell transplants also play a pivotal role in helping treat multiple diseases. 
• Stem cell transplantation is the procedure wherein the damaged cells of the body are replaced with healthy ones. This treatment is beneficial against cancer (like lymphoma, leukemia, neuroblastoma); blood-related disorders (such as sickle cell anemia, thalassemia) immune disorders, as well as metabolic disorders.³⁰ Stem cells extracted from both umbilical cord blood as well as adult bone marrow can be utilized in stem cell transplantations.³¹
• Regenerative medicine, or "stem cell therapy," is also a promising treatment option in trials for treating many ailments (such as strokes, burns, spinal cord injuries, Alzheimer’s disease, Parkinson’s disease, osteoarthritis, etc).  In stem cell therapy, damaged or dysfunctional tissues can be repaired using stem cells. Researchers have already had some success treating the tissues of the heart with modified bone marrow stem cells (in animals). ²²

Ending Note!

Did you know? The advances in modern medical science has made it possible for new parents to preserve the stem cells from their baby's umbilical cord blood? Yes, you heard us right. This advancement is called stem cell banking and it offers protection and care (from the potential diseases and disorders) of the newborn as well as the entire family (including siblings, biological parents, and maternal and paternal grandparents). 

Are you an expectant parent who wants to know more about the benefits of stem cell banking? Then all you have to do is give us a call @ 1800-266-5533!

If you wish to discover more fun facts about umbilical cord blood stem cells and the diseases it can cure, then do check out our “also read” section as well. Happy reading!