Engineering Applied to Human Aging to Increased Human Longevity

If only we could sustain our body’s organs and bodily functions as they are at age ten, we could expect to live longer without our bodies deteriorating with age. Scientists are developing an understanding of the nature of human aging in order to begin seriously planning ways to defeat the process. The human body can be compared to complex electronic equipment. An engineering approach to understanding aging of complex electronic and electrical equipment using reliability theory can be applied to understanding aging in humans. In general, engineering technology can be used to increase the life span of humans by slowing down the deterioration of critical body organs.

The remarkable improvement in early life conditions may be attributable to significant increase in human longevity through the process called “technophysio” evolution. Biological species, including humans, have been starting their lives under a highly adverse environment resulting in damage to organs especially when they are vulnerable. Early – life conditions may have significant effects on adult lifespan and on sex disparities in adult health and longevity.

Creation of a human body is far from being perfect and the body deteriorates over time. Electronic equipment like human bodies is also prone to failure and is defect-ridden. By applying the reliability theory of electrical and electronic equipment, the rate at which human bodies fall apart could be reduced to a low level. The engineering approach to understanding aging is based on ideas borrowed from the reliability theory. The reliability of a system refers to its ability to operate without failure according to a specified standard over a long period of time. So, the Reliability theory permits engineers to predict how a system with a specified architecture and level of reliability of its constituent parts will fail over time. In reliability theory, aging is defined through the increased risk of failure. More precisely, something ages if it is more likely to fall apart tomorrow than today.

Fault tree analysis, used in engineering is a top down approach to failure analysis. Starting with a potentially undesirable event called the “top” event; it then determines all possible ways failure can occur. A similar approach can be used to understand human body failure. If the risk of failure does not increase as time passes, then there is no aging in terms of reliability theory. By looking at human aging data, we can find a striking similarity between how living organisms and technical devices age and fail. In both cases, the failure rate follows a curve shaped roughly like a bathtub. The curve consists of three stages, which we call infant mortality, normal working, and aging periods. At the start of a machine’s life, failure rates are high; they then decrease with age. The same is true for most living organisms, including humans; this earliest vulnerability period is called the infant mortality period. Those computers and people that do not fail initially operate quite well for a time; this is the normal working period. Then, the aging period starts, when failure rate follows the exponential trajectory described by the Gompertz’s law of mortality. During the infant mortality period, both the organs and the technology become obsolete but do not age. During the normal working period the organism or machine neither deteriorates nor becomes more powerful, but stays constant and reliable. Finally, aging occurs when the body’s organs and technology deteriorate.

The Gompertz law of mortality in humans is similar to Weibull’s Power Law in civil engineering. Gompertz’s law of mortality says that the logarithm of death rate increases linearly with age. The Weibull’s Power Law used in civil engineering states that the logarithm of failure rates increases linearly with the logarithm of age. Another aging rule, called the compensation law of mortality becomes apparent in studies of the older end of population and mortality converges in later life. Redundancy takes care of three aging rules. First is the compensation rule, older people from different populations die at similar rates even if younger people from those populations have very different death rates. Redundant systems also mimic the way death rates level off in people over 100. The survival patterns of humans at extreme old ages are rather close to these linear dependencies suggesting that death rates, although very high, do not demonstrate further substantial deterioration with age. The failure kinetics of manufactured products also demonstrates the same non-aging patterns at the end of the product “lifespan”. This observation calls for a very general explanation of this apparently paradoxical “no aging at extreme ages” phenomenon.

Early development of living organisms produces an exceptionally high load of initial damage, comparable to the amount suffered during the entire adult life. We are born with a large amount of damage. Even small improvements to the process of early human development, ones that increase the number of initially functional elements, could result in a remarkable fall in mortality and a significant extension of human life. Indeed there is mounting evidence now in support of the idea of the fetal origins of adult degenerative diseases and early-life programming of aging and longevity. Even small progress in optimizing the early developmental processes can potentially result in a remarkable prevention of many diseases in later life, delayed mortality, and significant extension of healthy life span.

The engineering approach to understanding aging of complex electronic and electrical equipment using reliability theory seems to be a promising approach for developing a comprehensive theory of aging and longevity. Technology may actually allow us to significantly retard the pace of the deterioration of organs. Following the graphs of the death rate, one may be able to apply those results to individual body organs to augment their life-spans. As, over time, a computer slows down, our body organs similarly slow down. Just as a computer’s life span can be extended, so can ours with the application of the reliability theory. The reliability theory provides an explanation for many important aging related phenomena and suggests a number of interesting testable predictions. According to the mutation accumulation theory, aging is an inevitable result of the declining force of natural selection with age. We age because our makeup includes irreplaceable but redundant parts, many of which are defective, and we age as each of those parts inevitably malfunctions. Using such a theory can help focus biomedical research on interventions that can slow or control aging.

We could learn to replace our damaged organs, substituting the young and healthy for old and failing. Human life span can be greatly extended by replenishing aging organs with stem cells. Such regenerative medicine and tissue engineering may sound like a science fiction, but a growing number of scientists are taking the first steps to grow tissues and organs to replace failed ones. Research has demonstrated that engineering biological tissues may provide therapeutic alternatives for improving health and quality of life. Scientists are doing research in the areas of Tissue Engineering that focuses on design and fabrication of bio-conductive biomaterials. The goal of these activities is to develop technologies and devices that are applicable for generating functional cartilage tissue substitutes. Tissue engineering is an emerging field that aims to regenerate natural tissues and create new tissues using biological cells, biomaterials, biotechnology, and clinical medicine. The current scope of tissue engineering is primarily experimental but is rapidly expanding as developments occur daily. Laboratories around the world are making progress in building replacement lungs, kidneys, liver and heart tissue. Replacement body parts can be used to expand the human life span. Technology is growing significantly and is focused on devising mechanisms to effectively help human health. Electrical engineers are teaming up with gene jockeys and drug developers to invent new drug – delivery systems that marry electronics and semiconductors to biotechnology. New drugs need a degree of intelligence to get where they must go and to arrive on time, that is where semiconductors come in. The first disorders to be treated with “smart” drug delivery system will include predominantly older adults. The microchip would be implanted in the body and would serve as closed loop system like the engineering close loop systems. Two approaches are just now being tested for feasibility. One features an implantable microchip dotted with tiny drug reservoirs that pop open at the touch of a wireless telemetry button. The other relies on injections of nanometer scale beads of semiconductors that exploit the energy of electrons to kill cancer cells selectively. MicroChips, Inc. in Bedford Massachusetts is working on a 15 millimeter silicon microchip that is made using essentially the same techniques used in producing integrated circuits. Instead of transistors, the device is dotted with 100 tiny reservoirs that are filled with drug. Each reservoir is capped with a thin layer of platinum and titanium. It takes just a 4 volts zap to remove an individually addressable well covering to diffuse the drug. Technology is currently being developed to build intelligent drug delivery systems which can do closed loop sensing and drug administration.

Another method that can be used to expand the human life-span is a slow-release system. Advancis has developed a slow-release dosing system that packages up to four antibiotic-containing pellets into one pill. Once ingested, the pellets separate and release the same medicine in a series of bursts. Advancis claims the technology, called pulsys, because of the pulse-like drug delivery method, more effectively treats infections by repeatedly assaulting bacteria in between doses. In addition, quantum dots, crystals of II and VI cadmium selenide, have been introduced into cancer hunting are encapsulated in a protective coating. Quantum dots are injected into the blood streams which circulate until they find the cancer cell to which the antibodies stick. Infrared light shining on the suspected cancer site penetrates the tissue and causes the quantum dots to radiate photons. The photons pinpoint the cancer cell location and also cause the release of Taxol, which can then attack and kill the cancer cells. The Bioengineering Department at University of California at San Diego is taking the idea of drug targeting to an even finer level. The quantum dots are used for steering compounds to a particular compartment such as the nucleus, where the genes are within a cell, or in energy producing mitochondria. These technologies protect the body organs and slow the process of aging through the preservation of body parts.

Another example of using the technology is in the areas of wireless remote monitoring systems of older people. Companies including General Electric, Hewlett Packard, Honeywell and Intel are teamed up with Center for Aging Services Technology to encourage collaborative aging related technology development. Tiny battery powered sensors called motes are being developed at the University of California. Using wireless sensors to track the routine activities of daily life can greatly help in the diagnosis of neurological disorders such as Parkinson’s or Alzheimer’s disease. Parkinson’s can so far be diagnosed only through behavioral changes, principally changes in gait. Cardio-Net’s system of detection consists of a small three lead ECG monitor worn around the neck, and connected to a PDA device. The ECG monitor sends its data via wireless link to the PDA which evaluates and stores the waveform. A sudden change in data is transmitted over a cellular network to a monitoring center. Again, the technology is being used to extend human life span.

Human body is just one big system that runs by chemical gradient and electrical impulses. So, it should be possible to come up with replacement parts when bodies start to break down. The current efforts are being focused on so-called bio-hybrid or bio-artificial organs, which combine living cells with materials such as silicon and polymers. The hybrid organs get their structure from the inorganic material while relying on living tissue, grown from cadavers, and animals. Bio-hybrids are being tested outside the body and are at least five years away from reaching the market. These organs are being designed as implants. A good portion of the newest innovations involve growing cells in specifically ordered arrays on chips made of semiconductor material. Electrical impulses pattern the cells as they would be in a natural organ and stimulate them appropriately so they develop into needed tissues. Researchers have built tiny systems using semiconductor fabrication techniques to address diseases that are not either marginally treatable or untreatable. Most of the new bio-hybrid research projects target some of the primary disorders of aging: kidney failure, and heart disease. The number one organ needed right now is the kidney. Developers of bio-hybrid kidneys are targeting acute kidney failure first, because those patients are hospitalized and can be treated with a device that functions outside the body. Later, the developers hope to use what they learn to devise implantable devices that might extend lives of those with chronic kidney failure.

An experimental device called Renal Assist Device has been developed in University of Michigan that is now in its second of three phases of clinical trials for use as an adjunct in treating acute kidney failure. This device can be hooked up to a dialysis machine of a patient’s bedside. It is a bio-hybrid device because it contains human proximal renal tubule cells, kidney cells that normally recover useful chemicals from the fluid that remains after the blood has been strained through the kidney’s filters. Other examples of bio-hybrid devices are Liver Assist device and Lung Assist Devices. Although these devices are not yet implantable, they have been made in the labs. The bio-hybrid lung is based on a device that is as thick as a credit card. It is laced with micro-channels containing either air or blood, separated by thin membranes that mimic the alveolar wall. Even though several bio-hybrid organs have been developed, there are real concerns about how feasible these organ replacements will be as treatments for the disorders of aging. If bio-hybrid organs ultimately become widely available, there are also the staggering costs to consider.

In conclusion, the reliability theory suggests that there might be no single underlying aging process. Instead, aging may largely be a property of redundant systems. Such systems can have a network of destructive pathways, each associated with particular manifestations of aging, whether Alzheimer’s or Parkinson’s disease. Metaphorically speaking, our life span is a time bomb with many fuses burning at different speeds. Cutting off only one fuse may be inadequate; we need to take care of them all. Scientists are developing an understanding of the nature of human aging in order to start planning ways to overcome it. Technology is being used by scientist and doctors to understand aging and finding ways to increase the lives of humans by slowing down the deterioration of certain body organs. Engineers and scientists are now using neural networks to determine genetic characteristics for predicting disease outcome and identifying possible gene repair scenario. They are also using communications technology to understand cell signaling. Techniques used in engineering to understand system failures and to design redundancy can be applied in understanding human aging and to come up with ways to increase the length of human life. Doctors hope that a small chip could simply be implanted to deliver drugs at the necessary time. In reality, at our current level of technological sophistication, the immune system and scar-like tissues interfere with these kinds of chip responses making it increasingly difficult to make such technology function properly. Soon, however, it may be possible to turn these ideas and dreams into reality.

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