In Treatment for Aging Knees we discussed the potential for stem cell therapy to treat arthritic or aging knees. In the past, we have written a few general articles on stem cells, but this is first of more in-depth articles in what will be a series of stem cell therapy articles that we will publish throughout the remainder of this year. Today we are going to provide an overview of the many stem cell therapy clinical applications. We think you will be surprised at how much research has been done on the use of adult stem cells and its many clinical applications.
Lets’ get started.
What are Stem Cells?
First. what are stem cells? The human body comprises 37.2 trillions cells. There are 210 different types of cells the make up the human body. Cells (not just stem cells, but all cells) represent the smallest functional unit in the body. But, stem cells are special.
Stem cells have two unique features that the other 209 different types cells in the body do not have. Stem cells can 1) continuously divide or self-renew, and 2) they can differentiate into various other types of cells. Stem cells are found throughout the body, but are most abundant in the bone marrow, adipose tissue (fatty tissue), dental pulp, and circulating blood.
Stem cells repair the body. Without them it is estimated we would only live a year or two. The human lifespan is limited by the capacity of stem cells to keep repairing and replenishing tissue. We live as long as we have enough stem cells that can be activated to differentiate into other types of cells. The second part of that sentence is critical. Simply having stem cells is not enough. They must be activated to differentiate into more specialized cells that make up our various organ-systems. For reasons not yet fully understood our stem cells are less likely to differentiate as we age.
Stem cells represent only 0.001% to 0.01% of all nucleated cells (adult red blood cells circulating in the blood stream do not have a nucleus) and about 2 billion stem cells are produced daily in the bone marrow alone. That should put into perspective the ongoing need the body has to repair itself. Stem cells decline as we age. Though in culture (lab environment) they can continuously divide, they lose some of that capability as we age. In newborns one in every 10,000 cells is a mesenchymal stem cell. In adults that number drops to one mesenchymal stem cell in 250,000. Mesenchymal and hematopoietic (blood cells) stems cells are the most clinically useful stem cells, but there are other types of stem cells.
In might be helpful to think of a stem cell as a cell that is a “blank slate” that the body can program to become a specific cell type to repair or restore the body to normal function. They are cells held in reserve that the body can use when needed, just like you might keep money in reserve for emergencies.
Shortly after a heart attack patients have an increased number of stem cells circulating in the blood compared to the person who has not had a heart attack. The body knows there has been an injury and is trying to repair the damage. In some individuals those stem cells get activated and much of the heart damage is repaired. But, in others the stem cells never get activated to repair the damage. Why that is is unclear.
Stem cells must continuously divide, but they need to be activated to differentiate into more specialized cells when necessary (myocardial cells, neurons, muscle, bone, skin, etc).
Embryonic stem cells are pluripotent which means they can differentiate into any cell needed. Adult stem cells are multipotent which means they can differentiate into a limited number of closely related tissues. For instance, some multipotent cells differentiate into muscle, bone, and cartilage, all of which are closely related.
It may seem paradoxical but from a clinical application standpoint stem cells that have already been committed to differentiate into a specific tissue lineage are preferable over pluripotent stem cells. If you are trying to repair joint cartilage you want stem cells that are committed (already programmed) to becoming cartilage cells or chondroblasts. Basically, this means adults stem cells are more useful than embryonic stem cells in treating adult conditions. There are other reasons adult stem cells are preferred over embryonic stem cells which we will discuss in a future article.
There are also totipotent stem cells which have the capability to differentiate into complete organisms depending on the species from which the cells are coming from (human, dog, sheep, etc).
Stem cell therapy is one component of what is now being called Regenerative Medicine. Per the FDA, Regenerative Medicine is the translation of multidisciplinary biology and engineering science into therapeutic approaches to regenerate, replace, or repair tissues and organs in patients.
Regenerative medicine uses the body’s own repair and regenerative mechanisms to replace or regenerate diseased or injured tissues to restore or establish normal function. Normal or near normal function is the goal in regenerative medicine. That distinguishes if from much of conventional medicine which focuses on treating symptoms. Regenerative medicine turns science fiction into reality. Believe it or not, but through tissue engineering it is now possible to grow entire organs.
In addition to stem cell therapy Regenerative Medicine includes:
- Bio banking of stem cells
- Gene therapy
- Tissue engineering
- Medical delivery systems
- Cell therapy enhancers
Nowadays you can bank your own stem cells for future use. Stem cells from the umbilical cord are most ideal for this and an increasing number of parents (though still quite small) are having their newborn’s stem cells harvested and banked. There are several companies that provide that service. You can bank your stem cells at any age, but the younger you are when you do it the more high quality and functional stem cells you can bank.
Your body’s ability to produce stem cells is affected by your diet, quality of sleep, stress (including physical illness), and other factors.
Stem cells secrete hundreds and thousand of chemicals that actually do the repair work. Companies are identifying these compounds and developing unique delivery systems using nano particles to one day administered these compounds to induce tissue repair without the actual need to use stem cells. So that’s a brief glimpse of the future.
Stem Cell Therapy Clinical Applications
As of the first quarter of 2016 there were 669 clinical trials underway in the United States involving stem cell therapies. These are IRB studies (institutional review board) that the FDA oversees. Stem cell therapy is currently being studied in the treatment of the following common conditions:
- Congestive heart failure (CHF)
- Chronic obstructive pulmonary disease (COPD)
- Peripheral artery disease (PAD)
All of these diseases are prevalent, costly to treat conventionally, and significantly impact quality of life. Research involving stem cells is also being studied in the treatment of cancer, autoimmune disease, and neurodegenerative diseases (Parkinson’s and Alzheimer’s).
Congestive heart failure afflicts 5.1 million patients. One in nine deaths include heart failure as a contributing factor. Half those diagnosed with heart failure will die within five years of being diagnosed. Treating heart failure costs $32 billion annually. There are 108 clinical trials using stem cells to treat heart failure.
Chronic obstructive pulmonary disease is the third leading cause of death in the US affecting 12.7 million patients with 24 million individuals having some form of impaired lung function. Nearly $50 billion a year are spent to treat COPD. There are 17 clinical trials involving stem cells and the management of COPD.
Diabetes is becoming increasing common even among grade school aged kids. There are 1.9 million new cases of diabetes diagnosed each year. 87.3 million Americans are pre-diabetic. Sixty-eight percent of those with diabetes over age 65 will die from heart disease and 16% from a stroke. There are 132 clinical trials using stem cells to treat diabetes.
Peripheral artery disease affects 8 to 12 million in the US. Those with heart disease have a one in three chance of developing peripheral artery disease. Those who smoke are four times more likely to develop PAD. There are 43 clinical trials using stem cells to treat PAD.
Arthritis is the leading cause of disability in the US and affects one in five adults. Two-thirds of those with arthritis are under age 65 potentially impacting their lives for several decades. There are 74 clinical trials assessing the use of stem cells to treat arthritis.
In future articles we will discuss classification of stem cells, describe how they work, discuss how they are harvested, and discuss the techniques involved in using stem cells to treat specific conditions. We will also discuss the controversy regarding embryonic stem cells. All the conditions we just discussed can be managed with adult stem cells alone – one’s own stem cells. The controversy (ethical concerns) regarding embryonic stem cells can be completely avoided from a clinical application perspective. While embryonic stem cells may be of interest from a research perspective they hold little advantage (and have many disadvantages) over adult stem cells when it comes to clinical application which we will discuss in the future.