Growing a New Heart With Adult Stem Cells
Macleans.ca, March 18, 2009
Some species have a natural capacity for regenerating large quantities of their tissue whenever they suffer damage, the ultimate example of which is the salamander, in which spontaneous regrowth of entire limbs and even of large parts of its heart and brain have been well documented. Similarly, the popular aquarium resident, the zebrafish, has also been found to be capable of regrowing entire pieces of its heart, whenever necessary, due either to unfortunate accident or to the deliberate experimentation of curious humans. In any case, and regardless of the species, such regeneration is possible because of naturally occurring, endogenous, adult stem cells which exist within the organism precisely for this very reason: namely, to wait patiently until activated by injury or illness, at which time the adult stem cells valliantly come to the rescue to repair and replace damaged or missing tissue. However, biological regeneration is generally believed to be inversely proportional to evolutionary complexity, so that, in other words, the more biologically advanced a species is, the less natural regenerative ability that species possesses, and vice versa. Such a theory would explain why, for example, regeneration of entire limbs and organs is spontaneously seen in amphibians and fish but rarely in humans or other mammals.
However, such a theory may be incorrect.
Generally considered (at least by themselves) to be the most highly evolved and advanced species on the planet, human beings are now showing a natural ability for biological regeneration, at least at a cardiovascular level.
In developed countries such as the United States and Canada, cardiovascular disease continues to rank as the number one cause of death, and conventional medical therapies which consist of surgical procedures in combination with pharmaceuticals have not offered a satisfactory treatment for the disease and its numerous complications. Now, adult stem cells offer the first actual therapy which is capable not only of restoring full function to the damaged heart but also of regrowing healthy heart tissue; and such therapies are most successful when they work in combination with the body's own reservoir of endogenous adult stem cells.
Dr. Christopher Glover, an associate professor of medicine at the University of Ottawa and a cardiologist at the University of Ottawa Heart Institute, has been conducting a clinical trial in which endogenous adult stem cells are activated in patients following a heart attack. The clinical trial consists of 86 heart attack patients to whom a proprietary "drug" was given which activates the migration of each patient's own endogenous adult stem cells from the bone marrow into the bloodstream, from which the stem cells then automatically "home in" on, and target, the damaged tissue of the heart. As Dr. Glover describes, "There are some repairs that our bodies can [automatically] do. If we amplify the response, perhaps we'd get more repair." This treatment is meant to amplify the body's natural response mechanisms, and although the clinical trial is still in progress and has not yet concluded, the patients are already improving "even better than expected", according to Dr. Glover.
A similar study was conducted last year in an animal model in which an organic, collagen-based gel was injected directly into damaged tissue in laboratory rats and was subsequently found to stimulate angiogenesis, which is the formation of new blood vessels. The use of various agents, including externally derived stem cells, to stimulate naturally occurring endogenous adult stem cells is a popular and widely validated procedure that has been independently corroborated by a number of scientists in a number of studies conducted around the world.
The successful stimulation of the body's own adult stem cells extends far beyond the cardiovascular realm, however, and has already been applied to a wide range of therapies that require much more than mere angiogenesis. In fact, even in humans, a number of sources have documented the natural ability of the body's own adult stem cells to repair damaged tissue, even without external stimulation. For example, in human children prior to the age of approximately 10 years, the regrowth of entire fingertips that have been lost in accidents has been reported, as long as the wound is not deliberately sealed with a skin flap, which, unfortunately, is the usual de facto emergency treatment that is administered to such accidents, and which reliably prevents the natural regrowth of the finger by the artificial physical barrier that it creates. Without such physical barriers, however, and with a more enlightened medical approach, regrowth of digits is not uncommon in humanns. A particularly remarkable demonstration of such regeneration involved the case of Lee Spievack who, in his 60s, accidentally sliced off the end of one of his fingers in the propeller of a hobby shop airplane, after which he was treated with a powder that was applied directly to the injured area. Within four weeks, the missing half-inch of his finger completely regrew, including not only the flesh and blood vessels but also the bone and nail. The powder contained a proprietary extracellular matrix compound which stimulated and cooperated with the man's own endogenous adult stem cells in regrowing his missing finger. Likewise, the U.S. Army has already been applying adult stem cell technology to the regrowth of limbs for wounded soldiers returning from Iraq and Afghanistan. (Please see the related news articles on this website, entitled, "Grow Your Own Replacement Parts" and "Growing Miracles", dated February 6th and February 7th of 2008, respectively, each originally reported by CBS Evening News).
Regardless of the species, and across all species, the physiological body of each organism has a natural and strong genetic tendency to heal itself; even in humans, our very DNA is programmed to repair the cellular damage that results from the various injuries and illnesses of life. Regardless of the specific type of medical therapy that is used for any particular ailment, the greatest medical successes will result from those therapies that harness, to the fullest possible extent, the body's own natural healing abilities. In the realm of stem cells and regenerative medicine, we are thus far only barely able to glimpse the tip of the iceberg.
As Dr. Marc Ruel, a cardiac surgeon at the University of Ottawa Heart Institute, puts it, "We know it's going to work. We are living proof of it. Nature proves this concept every day."