What Are Stem Cells?

Stem cells are undifferentiated cells that have the ability to become any human cell in the body. To be considered a stem cell, cells must have two characteristics. The first is the ability to replicate itself in an unlimited fashion to produce progeny exactly the same as the originating cell. The second, which differentiates it from cancer cells, is the ability to give rise to a specialized cell type.

In adults, stem cells originate in the bone marrow. They are vital to repairing damaged tissues and forming new cells as organisms grow.

Because stem cells can develop into specialized cells in the body some researchers believe that stem cell-based therapies may be integral in treating serious illnesses such as type 1 diabetes, spinal cord injuries, Alzheimer’s disease, and strokes.

Stem cells
 luismmolina / E+ / Getty Images

Types of Stem Cells

There are three types of stem cells:

  • Embryonic stem cells come from embryos formed during an in vitro fertilization procedure. These cells are usually donated to science. They are pluripotent and therefore can develop into more than one type of cell in the body.
  • Adult stem cells replace old cells and supply new cells to the growing organism. Adult stem cells are multipotent, which means they can develop into some cells of the body, but not others. For example, a stem cell from the skin (an epithelial cell) can only make skin cells or a stem cell from the blood (a hemopoietic cell) can only make blood cells. 
  • Induced pluripotent stem (iPs) cells are made in a lab. Adult stem cells are re-engineered to be stem cells. Like their originators, these cells are multipotent. Although the first iPs cells were made in 2006, scientists have yet to discover how to reprogram adult cells into pluripotent stem cells.

Stem Cell Therapy Uses

Currently, only blood stem cells (called hematopoietic cells) are used to treat disease. These cells are found in the bone marrow and are used in bone marrow transplants.

Hematopoietic cells make all other types of blood cells, therefore these cells are vital in creating new cells in cancer patients who have lost their blood cells during radiation or chemotherapy or have genetic conditions, such as Fanconi anemia, that cause the bone marrow to fail.

Pluripotent stem cells have not yet been used therapeutically in humans because many of the early animal studies resulted in the formation of unusual solid tumors, called teratomas. Teratomas are made of a mix of cell types from all the early germ layers.

More recent animal studies have used more mature pluripotent cells with limited proliferative capacity, with much greater success. Some examples include: 

  • Creating insulin-producing cells responsive to glucose levels for animals with diabetes
  • Creating new myelinated neurons for animals with acute spinal cord injuries, and
  • Creating new retinal epithelial cells for animals with visual impairments. 

Commercial companies are currently in negotiations with the FDA regarding the possibility of advancing to human trials. Other animal studies have been conducted to treat several maladies such as Parkinson’s disease, muscular dystrophy, and heart failure.

Potential Treatments

Stem cell research is rapidly advancing and may help your health sooner rather than later. Researchers anticipate that stem cells will be used to create new tissues in the brain, heart, liver, and many other organs.

For example, one day healthcare providers may be able to treat people with chronic heart disease by growing healthy heart muscle cells in a lab and transplanting them into damaged hearts. Other treatments could target illnesses such as type 1 diabetes, spinal cord injuries, Alzheimer's disease, and rheumatoid arthritis.

While animal studies are preliminary they provide great insight into the future of stem cell research and its potential in modern medicine.

Challenges in Stem Cell Research

Stem cell therapy has become a very promising and advanced scientific research topic, but like all pioneering scientific and medical advances stem cells have to be vetted for ethical and safe use. Therefore, much more research needs to be done on stem cells before its use can be expanded. Challenges include:

  • Scientists must first fully understand how stem cells function in animal models.
  • The efficiency of stem cell-directed differentiation has to be improved to make stem cells more reliable and trustworthy for a regular patient.
  • Transplanting new, fully functional organs made by stem cell therapy would require the creation of millions of working and biologically accurate cooperating cells.
  • Identifying and isolating stem cells from a patient’s tissues is a major challenge.
  • Rejection by one’s immune system is a major barrier to successful stem cell transplantation. Therefore, human trials must confirm low rejection rates.
  • A more efficient process to create stem cells needs to be developed to mitigate DNA problems.
  • The medical and science communities must align on the scale, conditions for use, and side effects of stem cell treatment.
  • Some people may find using human embryonic stem cells morally and ethically controversial.

How Far Away Are We?

While the promise of stem cell therapy as a cure or treatment for a variety of diseases is highly touted much more research needs to be done before it is a viable therapeutic treatment option. The following obstacles that need to be overcome include:

  • The need for more human research. The genetics of mice and men differ, therefore more research needs to be done on the unique differences between human pluripotent and multipotent cellular biology. 
  • The common feature of unlimited cell division shared by cancer cells and pluripotent stem cells must be better understood in order to avoid cancer formation.
  • The ability to acquire large numbers of the right cells at the right stage of differentiation must be mastered.
  • Specific protocols must be developed to enhance production, survival, and integration of transplanted cells.
  • Clinical trials must be completed to assure the safety and efficacy of tstem cell therapy. 

Many in the science community believe that we are a long way from using stem cell therapy routinely, mainly citing health and safety concerns, but advances in medical technology may speed up the research capabilities of scientists who wish to answer these pertinent questions.

What’s Next?

Bringing such complicated procedures into general, widespread use requires interdisciplinary and international collaboration. Although stem cell research is in its early phases clinical trials are currently being done in the U.S. If you are interested in trying this therapy to treat a certain condition, ask your healthcare provider about trials that may be available in your area.

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institutes of Health. Stem cell basics. 2016.

  2. Yourgenome.org. What is a stem cell?. 2020.

  3. Biehl JK, Russell B. Introduction to stem cell therapyJ Cardiovasc Nurs. 2009;24(2):98-105. doi:10.1097/JCN.0b013e318197a6a5

  4. Zakrzewski W, Dobrzyński M, Szymonowicz M, Rybak Z. Stem cells: past, present, and futureStem Cell Res Ther. 2019;10(1):68. doi:10.1186/s13287-019-1165-5