Treatments classed as regenerative medicine help our natural healing processes work more rapidly and more effectively. These technologies can enable regeneration in missing or damaged tissue that would not ordinarily regrow, producing at least partial regeneration, and in some promising animal studies complete regeneration.
Strategies presently either under development, in clinical trials, or available via medical tourism include stem cell transplants, manipulation of a patient's own stem cells, and the use of implanted scaffold materials that emit biochemical signals to spur stem cells into action. In the field of tissue engineering, researchers have generated sections of tissue outside the body for transplant, using the patient's own cells to minimize the possibility of transplant rejection. Regenerative therapies have been demonstrated in the laboratory to at least partially heal broken bones, bad burns, blindness, deafness, heart damage, worn joints, nerve damage, the lost brain cells of Parkinson's disease, and a range of other conditions. Less complex organs such as the bladder and the trachea have been constructed from a patient's cells and scaffolds and successfully transplanted.
Work continues to bring these advances to patients. Many forms of treatment are offered outside the US and have been for a decade or more in some cases, while within the US just a few of the simple forms of stem cell transplant have managed to pass the gauntlet of the FDA in the past few years.
What Are Stem Cells?
Some of the most impressive demonstrations of regenerative medicine since the turn of the century have used varying forms of stem cells - embryonic, adult, and most recently induced pluripotent stem cells - to trigger healing in the patient. Most of the earlier successful clinical applications were aimed at the alleviation of life-threatening heart conditions. However, varying degrees of effectiveness have also been demonstrated for the repair of damage in other organs, such as joints, the liver, kidneys, nerves, and so forth.
Stem cells are unprogrammed cells in the human body that can continue dividing forever and can change into other types of cells. Because stem cells can become bone, muscle, cartilage and other specialized types of cells, they have the potential to treat many diseases, including Parkinson's, Alzheimer's, diabetes and cancer. They are found in embryos at very early stages of development (embyonic stem cells) and in some adult organs, such as bone marrow and brain (adult stem cells). You can find more information on stem cells at the following sites:
- Wikipedia on stem cells
- Stem Cells at the National Institutes of Health
- Stem Cell Basics from the NIH
Embryonic and adult stem cells appear to have different effects, limitations and abilities. The current scientific consensus is that adult stem cells are limited in their utility, and that both embryonic and adult stem cell research will be required to develop cures for severe and degenerative diseases. Researchers are also making rapid progress in reprogramming stem cells and creating embryonic-like stem cells from ordinary cells.
Progress in Stem Cell Research
Stem cell research is a growing, well-funded field, and as a result it is also a hot topic in the press. Not a week goes by without the announcement of a new and amazing advance, but these days most simply slip by without comment. The pace of progress is rapid, and so what would have been trumpeted in the popular science press a decade ago is now routine, carried out in scores of laboratories worldwide.
The first crop of simple stem cell therapies for regenerative medicine has reached widespread availability in the developed world. "Simple," because these therapies are on the level of transfusions. In most cases stem cells are obtained from the patient, then grown in a cell culture and the greatly expanded number of cells injected back into the body. New medicine doesn't get much simpler than that in this day and age. This is merely the start of a revolution in medicine, however, one will grow to become as large and as influential on health as the advent of blood transfusion or the control of common infectious diseases.
If you read enough of the literature, stem cells from your own body begin to sound like a miracle cure-all: extract them, culture them, return them to the body, and injured tissue begins to heal. It isn't anywhere near that straightforward, however, and this throwaway summary hides the many years of hard work by thousands of scientists required to bring us to this point, as well as the further years of hard work that lie ahead. Research continues, with a tone of excitement coming from the scientific community. They know they are onto something big.
Creating Recellularized Organs
Researchers have found what may be a shortcut to the growth of replacement organs from a patient's own stem cells. Called recellularization or decellularization, the process takes a human or animal donor organ and chemically strips the cells from it, leaving only the scaffolding of the extracellular matrix behind. Stem cells from the recipient are then used to repopulate the scaffold, and following the chemical instructions issued by the matrix they create a functioning organ ready for transplant that has little to no risk of rejection.
Since pigs could be used as a source of organs for transplantation, being of about the right size, decellularization is one potential way to eliminate donor organ shortages. The use of animal organs is still some years away from practical implementation, however. Human transplants have moved ahead, and in recent years decellularization has been used in the transplantation of tracheas and bladders in clinical trials. Meanwhile in the laboratory researchers have successfully transplanted decellularized lungs, kidneys, and hearts in mice and rats.
Ultimately decellularization is a stepping stone technology. It is necessary and useful because researchers cannot yet create an entirely artificial scaffold for a complex organ such as a kidney or a heart, complete with all of the chemical cues, fine structure, and mesh of capillaries necessary for its full function. That will become possible, however, at which point donor organs will no longer be needed.
Rejuvenating Aged Stem Cells
Stem cells in the adult body gradually relinquish their job of repair and maintenance with age, eventually causing tissue and organ failure. Based on the past decade of research, this occurs because stem cells become dormant in increasing numbers as rising levels of age-related cellular damage change the mix of chemical signals propagating through tissues. This reaction probably reduces the chances of cancer due to a damaged stem cell running amok, but at the cost of failing tissues. Researchers have found that by restoring signals to a more youthful mix, such as through infusing old tissue with young blood, aged stem cell populations can be restored to action and some of the impact of aging on our tissues might be reversed.
In recent years some of these stem cell activating signals have been identified. Researchers already regularly manipulate the genes and biochemistry of stem cells taken from patients for use in trials of new therapies: there is every reason to expect that future medicine will involve the repair and restoration of aged stem cells either prior to transplant or for existing cell populations within the body.
Regenerative Medicine and Human Longevity
Regenerative medicine will help to produce extended healthy longevity. In the decades ahead clinics will be able to repair some of the mechanical damage caused by aging, such as occurs in worn joints, but more importantly also reverse the decline in function of our stem cells, restoring stem cell maintenance tissue by tissue and organ by organ. At worst a regenerative treatment would be the replacement of a failing organ with a tissue engineered organ built to order from the patient's own cells, thus requiring major surgery, and at best such a treatment would adjust the cells within the failing organ, instructing them to repair the damage, with no surgery needed.
Aging damages every part of our bodies, however, including the stem cells required for regenerative therapies! Thus regenerative medicine on its own is not the full solution to aging: researchers must also address the root causes of age-related degeneration, the damage that accumulates within the molecular machinery of cells, and the metabolic waste products that accumulate in and around cells.
To add to this list, clinics must also become capable of reliably preventing and defeating cancer in all its forms, and also able to repair age-related damage to the brain in situ. Increasing risk of cancer with age cannot be prevented with regenerative medicine, and the brain cannot be removed and replaced with a new tissue engineered organ as will be the case for a liver or even a heart.
All in all these tasks will be a mammoth undertaking. Nonetheless, like all great advances in medicine, this is a worthy and noble cause. Today, hundreds of millions of people live in pain and suffering, and will eventually die, as a result of degenerative conditions of aging, many of which will be alleviated or even cured with near future advances in regenerative medicine. We stand within reach of the means to prevent all this death and anguish. We should rise to this challenge by supporting the researchers and research programs most likely to lead to meaningful progress.
Last updated: May 10th 2014.