Stem Cells 101

Recently, stem cells have received a lot of coverage in the popular press as the next medical miracle. While media claims often tend to exaggerate, the truth is stem cells posses significant potential to alter the way disease and injury are treated.

What are stem cells?

Stem cells are a special type of cell that has the potential to grow into many different types of cells. For example the same stem cell can grow up to be a brain cell or a heart cell or a lung cell. Essentially any type of cell you can think of! In musculoskeletal health we are especially interested in a sub set of stem cells referred to as mesenchymal stem cells:


As the figure illustrates, mesenchymal stem cells can mature into muscle cells (myocytes), fat cells (adipocytes), cartilage cells (chondrocytes), bone cells (osteoblasts), and tendon cells (tenocytes). Thus, mesenchymal stem cell therapy might offer a unique treatment option for diseases that result in unhealthy cartilage (osteoarthritis), unhealthy bone (osteoporosis), unhealthy muscle (sarcopenia), or unhealthy tendon (tendinopathy).

 What are the unique properties of stem cells that allow them to treat injury?

As noted before, stem cells have the potential to become many different types of new healthy cells. For instance, in osteoarthritis, cartilage has a hard time generating new cartilage cells. Stem cells might provide a source of healthy cartilage cells that in turn produce new cartilage and boost the joint’s mechanical properties so you experience less pain, less stiffness, and less weakness.

Additionally, stem cells can form many new mature cells, an important property if you are trying to replace a large swath of aged and decrepit tissue. Adding only one new cell would  be insufficient to dramatically alter the course of advanced disease. However, by adding a few new cells that produce many new healthy cells might provide the necessary cellular building blocks and signals for comprehensive regeneration.

Finally, stem cells positively impact the immune system.  Immune system dysfunction and chronic unhealthy inflammation are driving forces behind chronic joint, bone, muscle, and tendon disease.  Stem cells are able to help rebalance the immune system’s response to injury and orchestrate an overall health promoting milieu.

Where do stem cells come from?

Stem cells reside in many places in the body. Historically, the most common sources of stem cells for research and treatment include: bone marrow, fat, and umbilical cord blood.

The best source of stem cells for musculoskeletal health is controversial with valid arguments for and against one particular source. 

Bone Marrow

Stem cells from bone marrow are usually harvested from the area of your pelvis referred to as the iliac crest.  Stem cells from bone marrow are the best studied.  Some potential advantages of bone marrow derived stem cells are:

  • They are easily harvested from your pelvis.
  • They are your own cells so you don’t have worry about your immune system rejecting them, like often occurs with organ transplants.
  • Bone marrow derived stem cells seem to show a preference for forming new bone cells. So they might be very useful in treatment of diseases involving bone injury such as non healing broken bones, osteoporosis, or osteoarthritis with significant bony involvement.

A potential disadvantage of bone marrow derived stem cells is that depending on the age and overall health of the individual, the stem cells harvested might not have much new growth or healing potential.


Stem cells obtained from fat (adipose) are frequently harvested from your belly or your buttocks. Potential advantages of fat derived stem cells are:

  • They have the added benefit of removing some excess, unwanted fat from your body since the harvesting process is very similar to liposuction.
  • Like bone marrow derived stem cells, fat derived stem cells are your own cells; thus, you don’t have to worry about your immune system rejecting or destroying them.

As with bone marrow derived stem cells, a potential disadvantage of adipose derived stem cells is that depending on the overall health and age of the individual, the stem cells might have limited regeneration and health promoting capability.

Umbilical Cord Blood

Stem cells harvested from umbilical cord blood are not the patient’s own cells, so there is a higher risk of your immune system rejecting some, if not all of the stem cells and sabotaging the healing process. However, umbilical cord stem cells or so young and so vibrant that they have tremendous regenerative and healing potential.

How are stem cells delivered to injured areas?

Bone Marrow Harvest

In bone marrow harvesting, bone marrow is aspirated from the iliac crest region of your pelvis.  The stem cells are then isolated via a centrifuge, a machine that is able to separate different components of bone marrow. The stem cells are than injected back int the body. In this example into the hip joint via the femur (the thigh bone).


Adipose Harvest

In fat harvesting, fat is aspirated most commonly from the belly. The stem cells are than separated from fat and injected back into the body.

Stem Cell Expansion

In this schematic stem cells are removed from they body and expanded in the laboratory. The stem cells are seeded on a nutrient containing scaffold that magnifies their effectiveness. Additionally, their external environment can be manipulated to influence the type of cell they will mature into. For example, trying to influence the stem cells to become new cartilage cells, new bone cells, or new muscle cells. Finally, the more mature stem cells are re implanted into the body.

Future direction of stem cells?

Research will focus on determining the best source of stem cells for a particular disease, the optimal environment and scaffold to grow and re implant stem cells, and the frequency and number of stem cells to re implant.  Science and medicine are not there yet, but stem cell therapy is clearly a promising field.