By Michael G. Darwin, Steven B.Harris, M.D. and Sandra Russell, B.A.
The Life Extension Foundation's funding of anti-aging research at 21st Century Medicine laboratories means taking different pathways in the quest to extend the lifespans of people of all ages here, three of the researchers explain their progress to date.
Experimental gerontology seeks to understand how and why living organisms grow old and die. Gerontologists do not yet have a workable paradigm for how and why we age. As a result gerontologic research has been typically far removed from clinical application, while advances in clinical medicine often occur independently of any theoretical understanding of aging.
For example, physicians did not need to understand the inflammatory "cascade" to make very good use of aspirin. Indeed, aspirin was used for nearly a century before anyone began to understand its mechanisms of action. Similarly, today we are using a variety of drugs and nutrients to fight aging and age-associated diseases without fully understanding how aging works.
Right now, the only way to find out if potential anti-aging therapies really work is to conduct lifespan studies in a relevant animal model. There are several barriers to getting this kind of research done. The first is that it takes time, considerable skill and money. The second is that many agents with anti-aging potential cannot be patented, which discourages investment in lifespan studies.
But at the Life Extension Foundation, our major concern is not how much money we can make from funding research, but how vital the research is for anti-aging purposes. To that end, the Foundation is funding long-term lifespan studies in laboratory mice (the Lifespan Project) to determine the effects of various nutrients, hormones and drugs on lifespan, aging and the diseases of aging.
For those who can't wait to find out how to slow the aging process throughout the lifespan, we're also funding a series of studies aimed at achieving rejuvenation, called the Rejuvenation Project, on gaining a partial reversal of the aging and degenerative changes associated with advancing age. Among the agents we plan to investigate in our quest for authentic rejuvenation therapies is growth hormone, which has been proven to have potent anti-aging effects in humans, and has extended the mean lifespan of aging mice in dramatic fashion.
The first study in the Rejuvenation Project is now well underway and is expected to be completed this year. It is called the Genesis Experiment and is a classic example of research that could not be done in a university or industry setting.
For many years it has been known that adult animals (including humans) can be re-populated with missing cell types without which they would otherwise suffer death or disease. Perhaps the most common example of this is the administration of bone marrow via intraperitoneal or intravenous injection to re-populate the marrow of a patient who has undergone chemotherapy and/or radiation treatment for cancer. Similarly, fetal cell transplants have been used to repopulate neuron-depleted areas of the brains of both rats and humans with Parkinson's disease. Fetal neurons also have been used to seed the forebrains of aged animals with cholinergic neurons in an attempt to improve cognitive function.
Two Theories of Aging
Two theories of aging are the immunologic theory of aging and the finite number of cell divisions, or "Hayflick Limit," theory of aging. These two theories are not exclusive of each other. Both state that aging occurs in part or in whole as a result of a decline in the population of young, viable, dividing cells in the body as a whole, or in the immune system in particular.
It would be interesting (and very useful) to know if the administration of "youthful" stem cells, the formative cells that give rise to the various differentiated tissues of the body that comprise our organs and tissues, can extend lifespan in aged animals. For many years, animal fetuses, principally from sheep, have been homogenized into cells and given to treat aging. This "cell therapy" treatment was invented by Swiss physician Dr. Paul Niehans and has been popularized by European physicians such as Hans Schmidt in Germany. Many remarkable claims have been made for this treatment, but there are theoretical and practical reasons to suspect that it does not work.
As originally put forth by Dr. Niehans, the fetal cells from sheep are supposed to "take" and colonize the elderly human host, rejuvenating him in the process. The problem is that even in the same species, each individual is genetically and immunologically unique and such foreign tissues are likely to be rejected. Indeed, even tissues from a brother or sister (unless from an identical twin) are rejected without the use of powerful and dangerous immunosuppressive drugs, such as cyclosporine, which depress immune function.
A more appropriate animal model for cell therapy would be to administer more or less genetically identical fetal tissue to old animals. Such an experiment could answer important questions about how aging occurs, and if rejuvenation of old animals are possible by giving them young stem cells. One way to do this experiment is to use animals that are so inbred that they are nearly identical genetically. In such animals, tissues can be transplanted to any other animal of the same strain without concern about rejection.
The Fischer 344 rat is such an animal. The Fischer 344 has been inbred over hundreds of generations so that all individuals in the strain have histocompatible tissues. Another advantage to the Fischer 344 is that it is a widely used animal in biomedical research (and in gerontology) and thus old animals, or so-called "retired breeders," are readily available at a reasonable cost. Similarly, "timed pregnant" females can be ordered so that histocompatible fetal tissue is available on demand at precisely the right time.
On Sept. 24, 1996, 30 Fischer 344 male rats, 20 months of age (the human equivalent of 60 to 65 years of age) arrived at the facilities of 21st Century Medicine in Southern California. Each animal was placed in a separate cage, and on Sept. 29, the animals were randomly divided into three groups of 10 each. One group (experimental) was given complete tissue samples from fetuses removed from time-pregnant females by intraperitoneal administration.
A Very Good Model
Another group (the control) was given the vehicle solution in which the fetal cells were prepared (Hank's Balanced Salt Solution), in the same manner as the experimental group. A third group (also a control) was given liver and spleen tissue from a non-pregnant female of the same age, as used to provide the complete fetal tissues. The purpose of this last group was to serve as a control on the sterile preparation technique used to generate the fetal tissues. The spleen of adult animals also contains many immune cells, including stem cells.
The mean lifespan of male Fischer 344 rats is about 766 days. Not surprisingly, mortality has been brisk and, four months into the study, only 13 animals remained alive out of the 30 that were present when the study began.
We already have a pretty good idea of the effects of fetal cells administration on mortality and morbidity, but those results will not be revealed until the study is over. More importantly, we have developed what we think is a very good model for rapidly determining if an intervention is effective at reversing the aging process.
These studies are not easy to do. Every aspect of the animals' care must be tightly controlled if the data are to be meaningful. Day-night cycles, temperature, humidity, diet and husbandry must be meticulously attended to. Additionally, the animals must be weighed weekly, and also checked twice daily so that dead animals can be promptly necropsied to determine the cause of death.
Substantial upgrades to the 21st Century Medicine facility were made to carry out the Genesis Experiment, as well other experiments in the Rejuvenation Project, which will follow. These upgrades have paid off handsomely. There have been no significant problems. In fact, things have gone about as well as we could have hoped for. The animals mostly are dying of cancers, with an occasional death from pneumonia or congestive heart failure. The survival curve of the animals closely matches that of the best curves in the literature. Data acquisition and animal husbandry have proceeded smoothly.
Unlike the pilot Genesis Experiment, future studies in the Rejuvenation Project will include more tests. For example, the growth hormone study will probably include laboratory evaluations of blood and more detailed measurement of the animals' physiological response to the treatment. In the Genesis Experiment, the only endpoints have been cause and time of death. Effects of treatment on lean body mass, total body fat, blood chemistries, immune function and other parameters of interest were not determined.
Increasing The Monitoring
However, as other agents and approaches to slowing or reversing aging in the aged adult animal are evaluated, there will be various types of functional and biochemical monitoring. In fact, one of the features built into these experiments will be to increase the frequency and scope of monitoring if a favorable response to treatment is detected. Sentinel animals not included in the core group and used to determine the effect of the treatment on lifespan will be used for blood drawing and other invasive procedures so that the effects of the treatment on lifespan can be separated from "perturbations" induced by laboratory sampling.
One of the most impressive things to all the investigators involved in this experiment has been the rapidity with which these old animals decline and die. When they arrive they are old, but free of overt disease. Very rapidly they begin to experience the sharp increase in mortality that any aged population of mammals experiences. Relatively healthy animals become ill, lose weight and die, all in a matter of weeks to months. Any intervention capable of arresting or reversing this rapid decline will be one well worth investigating further.
The Life Extension Foundation is probably the only organization in the world that will be funding this type of interventive research, which has the potential of benefiting you in the near future, in extending the lifespan of people of all ages, not just members of future generations.
Foundation president and founder Saul Kent is almost 58 years old, and many foundation members are older than he is. They are extremely interested in finding methods to extend their lifespans before it's too late. That's why the Rejuvenation Project will be an integral part of the life extension research funded by the Foundation in the years to come.