What are Stem Cells?

Stem cells are cells that give rise to all types of tissue within the body. They have a number of special features that make them unique. They are capable of self-renewal, meaning they divide or multiply to maintain a population of identical cells that can be used to repair and regenerate tissue throughout the body. They are also capable of differentiating into different types of cells (such as muscle, bone, cartilage, neurons, etc) that can replace or repair damaged or diseased organs throughout the body.

Figure 1. Stem cells are capable of self-renewal, which ensures a persistent population of stem cells. They are also capable of differentiating into specialized cells such as bone, cartilage, muscle and neurons. 

There are different types of stem cells depending on where they come from. Embryonic Stem cells means that they are obtained from human embryos which are the cells that are formed when the female egg and male sperm join and begin to develop into a person. These cells are referred to as Pluripotent, meaning they are capable of becoming any type of cell in the body.

Adult stem cells are found in all tissue within the body that contains blood vessels. They are usually referred to as Mesenchymal stem cells or MSC’s. Adult stem cells are more restricted in their ability to differentiate and are therefore called Multipotent. They can differentiate to become bone, cartilage, muscle, fat, nerve cells and other types of mature cells in the body. They are located along the blood vessels where they can monitor the local environment and mobilize to areas of tissue damage in order to initiate the healing process. Mesenchymal stem cells secrete a variety of growth factors and other chemicals that induce cell production, along with the formation of new blood vessels (angiogenesis), necessary for tissue repair.

Figure 2. Stem cells manufacture and secrete many chemicals that perform a number of functions. They can attract other cells, promote blood vessel formation, modify cell function, etc, which aids tissue repair and regeneration. 

These local actions of stem cells are called paracrine functions. Stem cells produce and release a host of chemicals that function in several ways to recruit other cells involved in tissue repair, restore cells to normal function and suppress processes that lead to tissue damage. Described as the body’s drugstore, the cells are involved in the regulation of cellular activity, biochemical and metabolic functions throughout the body. They help maintain the body in a state of good health and to repair damage and restore normal function when things go astray.

There are many chronic diseases caused by abnormal function of the body’s own repair or immune system. Chronic inflammatory diseases such as rheumatoid arthritis, ulcerative colitis, chronic cystitis and prostatitis involve a persistent imbalance in cells such as T-helper cells and macrophages as well as the chemicals they produce. This results in irritation and damage to tissue, which often leads to pain and organ dysfunction. Stem cells can release chemicals that can correct the imbalance, which can bring repair of damaged tissue and the return of normal function in affected organs. Autoimmune diseases such as Multiple Sclerosis, Lupus, Crohn’s disease, etc result from the body’s immune system attacking itself, resulting in tissue damage. Diseases such as Asthma and Chronic Obstructive Pulmonary disease (COPD) result in damage to the lungs that can leave people short of breath with low exercise tolerance. Diabetes is another condition in which the cells in the pancreas do not function properly, leading to abnormal regulation of sugar within the body. This can lead to damage to the eyes, kidneys and other organs.

Stem cells are usually obtained from either bone marrow or adipose (fat) tissue because they are present in large numbers and are easy to obtain. They are separated from other components such as blood cells by placing them in a centrifuge, which spins at high speed and separates the different components based on weight. The stem cell component is then isolated and injected into the person to obtain the desired effect. Stem cells can be injected directly at the site of injury or damage such as into an arthritic joint or they can be injected into the blood stream via an intravenous catheter. Studies have shown these approaches to be safe. Stem cells have also been injected into the spinal fluid for treatment of diseases such as MS or ALS. They can also be injected into degenerative discs to reduce pain and halt degeneration of the spine and stimulate repair of the disc. All of these types of treatments have been tested in animals such as rats and mice. They have also been done in people and have shown benefits with very few side effects or complications. However, these types of treatments are still considered experimental and there is still a lot of research that needs to be done to determine what type of treatment works best for different diseases. It is currently not known how long these types of treatments last, if they need to be repeated and if so how often and when. There are still many questions to be answered and it is future research that will help answer these questions. Research is slow and expensive but is necessary.

Research has shown that stem cells can reset the immune system imbalance in favor of tissue repair. They can decrease or even reverse the damage caused by inflammation. Stem cells can also rescue cells that are in the process of dying (apoptosis) due to lack of oxygen, along with damage caused by trauma or exposure to toxins. Stem cells also produce chemicals that can fight infections caused by bacteria.

Figure 3: Stem cells release a large number of chemicals that can mediate or regulate a variety of processes. They restore the balance of cell function in inflammatory and autoimmune diseases, prevent cell death, regulate tissue repair and regeneration and a host of other functions. 

Stem cells can be guided to differentiate into different types of cells depending on their local environment. In tissue damage caused by trauma, lack of oxygen (stroke or heart attack) or degenerative diseases such as Alzheimer’s Disease and Parkinson’s Disease there is a progressive loss of cells leading to neurological symptoms such as dementia, tremor and mobility problems. In Osteoarthritis there is progressive loss of cartilage cells resulting in pain in the joint, swelling and reduced mobility. Stem cells have the ability to differentiate into different types of cells that can be used to repair or regenerate tissue, which can halt the progression of the disease, decrease pain and restore functions such as thinking and mobility . For example, injection of stem cells into arthritic joints can stop the inflammatory process that leads to joint damage and can become cartilage-producing cells to repair the damage. This can relieve pain and delay the need for joint replacement surgery sometimes for years.

Stem cells were first identified in the 1960’s. Knowledge about what they are, where they are located and what they do in the body has grown over the past 40 years, and the potential for their use in treatment of a host of medical conditions has been a source of intensive research. Their use in veterinary medicine has been accepted for years. Stem cell therapy for a host of human medical diseases is still in the early stages of development and is still considered experimental. Stem cells have been used in the treatment of stroke, MS, Parkinson’s disease, Osteoarthritis, Chronic lung disease, Heart disease, burns, chronic wounds and a variety of other conditions.

Government regulations allow for the use of autologous, minimally manipulated tissue. That means cells that are taken from one area of a person’s body are then re-injected back into the same person. The most common sources of stem cells are bone marrow and adipose (fat) tissue because they are easy to harvest with very low risk of complications. They are processed immediately and administered within hours, making the whole process timely with low risk. Autologous means that the cells are obtained from the same person who will undergo the treatment. This means there is no risk of rejection or disease transmission, which are both concerns when using cells obtained from a donor source such as amniotic or umbilical cord.

Allogeneic stem cells are cells that are obtained from other people who donate their cells to be used for treating different medical conditions. This is similar to blood donors who donate blood for transfusion to people in need of blood. The cells are usually harvested from a number of different donors and pooled together to increase the number before being administered to the patient. Therefore there is the potential for disease transmission and for rejection of the cells by the person who is receiving them. The process used for allogeneic stem cell transplants require more extensive preparation, such as expansion in tissue culture where they can be stimulated to differentiate into mature cells such as myocardial cells, cartilage cells, bone, etc. Expansion in tissue culture can result in large number of cells. However, these processes can also result in the loss of the some of the functions that are present in the minimally manipulated stem cells.

In the future, we may be able to harvest stem cells from a person with a specific disease such as diabetes. We will be able to treat the stem cells with specific chemical factors that cause the cells to differentiate into insulin-producing islet cells and inject them back into the person to cure their diabetes. As well, we may be able to use 3D printing to form a kidney, harvest stem cells, and treat them with specific chemicals that result in the formation of a fully functioning kidney that could be implanted without the need for anti-rejection medication. The sky is the limit for the future of stem cell therapy. However this is going to take many years of research and clinical trials to get it right.