New bio-medical scientific studies have recently discovered that stem cells can be used medically to recreate live healthy tissue to replace damaged or diseased tissue.

In other words, instead of repairing a damaged liver, shoulder joint, or heart, imagine if you could simply create a new liver, shoulder joint or heart!

That is why there is so much popular “Buzz” about stem cells these days. Major universities all over the world are now involved in conducting scientific research on stem cells in order to discover more about these elemental cells and the way they function.

A vial of stem cells being removed from cryogenic storage.

Stem cells can be collected from several sources in the human body, and once they have been properly prepared, Regenerative Medicine specialists around the world report they can provide useful – even miraculous – treatments for all organ systems of the human body. In this comprehensive post, we will discuss more about this complex, compelling, exciting and life-changing topic.

What are Stem Cells?

Stem cells refer to “original” cells that are “undifferentiated” which means they have not yet become cells that are a part of a specific organ system. In fact, stem cells have the potential to become “differentiated” and become specialized cells that are transformed into different organs tissue.

When a stem cell divides, it splits into 1. a copy of itself (self-renewal) and 2. a specialized cell (differentiation).

Like the cells of any organ such as your kidney, skin, or liver, differentiated cells have a specialized purpose that perform a specific function.

Before stem cells differentiate into specialized cells, they can divide through the process of mitosis which leads to the production of more stem cells. This is called the self-renewal capacity which ensures that every organ in your body always has enough stem cells in it that can create, repair and replace tissue that is damaged, diseased and no longer functioning properly.

Humans have two types of stem cells: embryonic stem cells and adult stem cells.

Human Embryonic Stem Cells

Human embryonic stem cells (hESCs) are the initial group of cells that comprise the embryo during the first few days after conception. Each of these embryonic stem cells has the potential to differentiate into every type of human cell and all the organ systems of a developing baby.

hESCs can be expanded in the lab forever (the creation of more cells).  As a result, they hold enormous promise for developmental research, drug screening, cell-based therapy, and disease modeling. A thorough understanding of the signaling processes driving hESC differentiation into early cell lineages is critical. Significant progress has been made in understanding the growth factors, intracellular pathways, and transcriptional regulatory networks that regulate hESCs self-renewal and differentiation processes.

Human embryonic stem cells exist only in human embryos that are no more than 1 week old. In other words, embryonic cells can be found only during the very first week of the development of a human’s embryo. This first week of development is called the blastocyst stage.

During the first week of embryo development, called the blastocyst stage, is where embryonic stem cells are procured. This stage also contains what will become the placental stem cells or Mesenchymal Stem Cells (MSCs).

In the medical world, these embryos usually come from In-Vitro fertilization clinics, where human eggs are fertilized with human sperm under laboratory conditions and then frozen for future implantation into the mother when she is ready to carry a baby.

After the first week of development, the blastocyst develops two layers of cells: the outer layer of cells forms the placenta, amniotic fluid and the umbilical cord, while the inner layer will eventually differentiate into different cell “lineages” in order to create all the necessary structures and organs of a complete human baby that will grow into an adult (see above image). All this leads to the production of specialized cells that form the different organ systems.

Embryonic Cell “Line” or Cell “Lineages

As original embryonic stem cells develop, three different “lines” of cell types emerge. The three germ layers – mesoderm, endoderm, and ectoderm – create the cellular blueprint for all the tissues and organs that will form during embryonic development. Normal embryonic development requires the precise creation of all three layers as well as the complex signaling between each of them.

Embryonic stem cells develop into 3 different “lineages”.

Endoderm (inner layer)

During embryonic development, the endoderm is the innermost germ layer that develops the linings of the respiratory and gastrointestinal passages, as well as their related organs such as the liver and pancreas.

Mesoderm (middle layer)

Mesodermal cells are the most prevalent in the human body, representing a wide range of cell types such as the musculoskeletal system (bone, cartilage, and muscle), cardiovascular system (heart, blood, and blood vessels), and connective tissues.

Ectoderm (outer layer)

Organs derived from embryonic ectoderm include mammary glands, CNS, external ear, melanocytes, cornea, brain, nerves, teeth, eyes, and the epithelium of the skin.

Every cell in a human body comes from one of these three fundamental cell lineages.

Human Adult Stem Cells

The second category, Adult Stem Cells, are the stems cells that can be found in each of the developed organ systems. These organ specific stems cells, are in charge of repairing and regenerating new cells and tissue of their specific organ.

For example, stem cells found in the liver take care of liver cells, and can generate new liver tissue whenever needed. Accordingly, kidney stem cells do the same for kidneys, and skin stem cells do that for skin. Thus, each organ system has stem cells that are specifically programed and equipped to care for, repair and regenerate tissue of that organ.

Each organ system has adult stem cells that are specifically programed and equipped to care for that organ.

Adult stem cells that are found in different organs are also known as “somatic” stem cells. They can remain in a non-dividing state for years. However, when the organ tissue becomes injured or diseased the stem cells become activated and start dividing. These somatic/organ stem cells have the capacity to divide indefinitely in a process called “self-renewal”.

Current scientific understanding reveals that adult stem cells, as a group, can only supply derivative cells indefinitely if they are replenished through cell division. Self-renewal is defined as a balanced combination of stem cell division and differentiation that results in a relatively constant number of stem cells. Importantly, both the essential replenishment function of adult stem cells and the associated “self-renewal” traits of differentiation, division, and lifetime persistence apply to the stem cell community within that organ as a whole. They are not always applicable to each individual stem cell.

Whether or not stem cells from a specific organ can also become other types of organ cells and tissues is still a controversial and debatable subject.

Harvesting Adult Stem Cells

When a doctor needs human adult stem cells to treat a patient, where do these stem cells come from? There are three places in the body of the patient where a doctor can collect (“harvest”) the patient’s own adult stem cells:

Bone marrow

These stem cells can be harvested by extraction, which involves drilling into the patient’s bone, usually the iliac crest bone (part of the pelvis bone just above the hip), or a leg bone (Femur, in the thigh – or Tibia, below the knee). As you can imagine, this is not a very pleasant procedure.

Bone marrow transplantation can cure numerous blood illnesses as well as other diseases, such as solid tumors. 

Adult stem cells can be harvested from the patient’s femur bone

Lipid Cells

Because of their abundance in fat tissue and simplicity of extraction via liposuction, adipose-derived mesenchymal stem cells (ASCs) are of great interest. Stem cells found in the adipose (fat) tissue require extraction by liposuction. This too is not a very pleasant procedure.

Furthermore, ASCs can grow rapidly and release significant quantities of pro-regenerative substances. Pilot investigations with human ASCs in vivo have demonstrated their potential to mend calvarial abnormalities and improve vascularization of composite ischemic tissue.

ASCs offer several major advantages over other MSC populations, including the diminishing quantity of BM-MSCs available with age, the vast amounts of bone marrow required, and the procedural hazards associated with bone marrow harvest.

Peripheral Blood

Increasing data suggests that, in addition to BM, peripheral blood (PB) may be a source of stem/progenitor cells for clinical use, including haematopoietic stem cells, endothelial progenitor cells, and MSCs.

Adult stem cells have been found to patrol the bloodstream and circulate across peripheral organs, both healthily and pathologically, which may be essential for tissue homoeostasis and tissue repair. At a steady state, MSCs are present in the peripheral circulation at a relatively low frequency.

However, in response to injury signals, the number of MSCs in the bloodstream increases rapidly. Thus, in recent years, PB, which may be collected with minimum invasion, has been recognized as an important alternative source of MSCs for cell therapy.

Processing Adult Stem Cells

In each of the above 3 processes, the harvested tissue must pass through specialized machines where the harvested stem cells are cleansed, purified and concentrated in preparation for being re-introduced back into the body of the donor, who is also the patient.

Depending on how the prepared stem cells are being administered, they may be prepared in different ways and combined with different formulations.