Artificial organ

An artificial organ is a man-made device that is implanted or integrated into a human to replace a natural organ, for the purpose of restoring a specific function or a group of related functions so the patient may return to a normal life as soon as possible. The replaced function doesn't necessarily have to be related to life support, but often is.

Implied by this definition is the fact that the device must not be continuously tethered to a stationary power supply, or other stationary resources, such as filters or chemical processing units. (Periodic rapid recharging of batteries, refilling of chemicals, and/or cleaning/replacing of filters, would exclude a device from being called an artificial organ.) Thus a dialysis machine, while a very successful and critically important life support device that completely replaces the duties of a kidney, is not an artificial organ. At this time an efficient, self-contained artificial kidney has not become available.

Reasons

Reasons to construct and install an artificial organ, an extremely expensive process initially, which may entail many years of ongoing maintenance services not needed by a natural organ, might include:

Life support to prevent imminent death while awaiting a transplant (e.g. artificial heart)
Dramatic improvement of the patient's ability for self care (e.g. artificial limb)
Improvement of the patient's ability to interact socially (e.g. cochlear implant)
Cosmetic restoration after cancer surgery or accident

The use of any artificial organ by humans is almost always preceded by extensive experiments with animals. Initial testing in humans is frequently limited to those either already facing death, or who have exhausted every other treatment possibility. (Rarely testing may be done on healthy volunteers who are scheduled for execution pertaining to violent crimes.)

Although not typically thought of as organs, one might also consider replacement bone, and joints thereof, such as hip replacements, in this context.

Organs

Brain

Neurostimulators, including deep brain stimulators, send electrical impulses to the brain in order to relieve Movement disorders, including Parkinson's disease, as well as epilepsy, depression, and other conditions such as increased bladder secretions. Rather than replacing existing neural networks to restore function, these devices often serve by disrupting the output of existing malfunctioning nerve centers to eliminate symptoms.

Cardia and pylorus valves

Artificial cardia and pylorus can be used to fight esophageal cancer, achalasia and gastroesophageal reflux disease. This pertains to gastric repairs, specifically of the valves at either end of the stomach.

Corpora cavernosa

To treat erectile dysfunction, both corpora cavernosa can be irreversibly surgically replaced with manually inflatable penile implants. This is a drastic therapeutic surgery meant only for men who suffer from complete impotence that has resisted all other treatment approaches. An implanted pump in the (groin) or (scrotum) can be manipulated by hand to fill these artificial cylinders, normally sized to be direct replacements for the natural corpora cavernosa, from an implanted reservoir in order to achieve an erection.

Ear

Main article: Cochlear implant

While natural hearing, to the level of musical quality, is not typically achieved, most recipients are pleased, with some finding it useful enough to return to their surgeon with a request to do the other.

Eye

Main article: Visual prosthetic

The most successful function-replacing artificial eye so far is actually an external miniature digital camera with a remote unidirectional electronic interface implanted on the retina, optic nerve, or other related locations inside the brain. The present state of the art yields only very partial functionality, such as recognizing levels of brightness, swatches of color, and/or basic geometric shapes, proving the concept's potential. While the living eye is indeed a camera, it is also much more than that.

Various researchers have demonstrated that the retina performs strategic image preprocessing for the brain. The problem of creating a 100% functional artificial electronic eye is even more complex than what is already obvious. Steadily increasing complexity of the artificial connection to the retina, optic nerve or related brain areas advances, combined with ongoing advances in computer science, is expected to dramatically improve the performance of this technology.

For the person whose damaged or diseased living eye retains some function, other options superior to the electronic eye may be available. ♦

Heart

While considered a success, the use of artificial hearts is limited to patients awaiting transplants whose death is imminent. The current state of the heart devices are unable to reliably sustain life beyond about 18 months.

Artificial pacemakers are electronic devices which can either intermittently augment (defibrillator mode), continuously augment, or completely bypass the natural living cardiac pacemaker as needed, are so successful that they have become commonplace.

Ventricular assist devices are mechanical circulatory devices that partially or completely replace the function of a failing heart, without the removal of the heart itself.

Artificial limbs

Artificial arms and legs, or prosthetics, are intended to restore a degree of normal function to amputees. Mechanical devices that allow amputees to walk again or continue to use two hands have probably been in use since ancient times, the most notable one being the simple peg leg. Surgical procedure for amputation, however, was not largely successful until around 600 B.C. Armorers of the Middle Ages created the first sophisticated prostheses, using strong, heavy, inflexible iron to make limbs that the amputee could scarcely control. Even with the articulated joints invented by Ambroise Paré in the 1500s, the amputee could not flex at will. Artificial hands of the time were quite beautiful and intricate imitations of real hands, but were not exceptionally functional. Upper limbs, developed by Peter Baliff of Berlin in 1812 for below-elbow amputees and Van Peetersen in 1844 for above-elbow amputees, were functional, but still far less than ideal.

The nineteenth century saw a lot of changes, most initiated by amputees themselves. J. E. Hanger, an engineering student, lost his leg in the Civil War. He subsequently designed an artificial leg for himself and in 1861 founded a company to manufacture prosthetic legs. The J. E. Hanger Company is still in existence today. Another amputee named A. A. Winkley developed a slip-socket below-knee device for himself, and with the help of Lowell Jepson, founded the Winkley Company in 1888. They marketed the legs during the National Civil War Veterans Reunion, thereby establishing their company.

Another amputee named D. W. Dorrance invented a terminal device to be used in the place of a hand in 1909. Dorrance, who had lost his right arm in an accident, was unhappy with the prosthetic arms then available. Until his invention, they had consisted of a leather socket and a heavy steel frame, and either had a heavy cosmetic hand in a glove, a rudimentary mechanical hand, or a passive hook incapable of prehension. Dorrance invented a split hook that was anchored to the opposite shoulder and could be opened with a strap across the back and closed by rubber bands. His terminal device (the hook) is still considered to be a major advancement for amputees because it restored their prehension abilities to some extent. Modified hooks are still used today, though they might be hidden by realistic-looking skin.

Liver

Main articles: liver dialysis § Liver dialysis devices and Hepatocyte

HepaLife is developing a bioartificial liver device intended for the treatment of liver failure using stem cells. The artificial liver, currently under development, is designed to serve as a supportive device, either allowing the liver to regenerate upon acute liver failure, or to bridge the patient's liver functions until a transplant is available.^[1] It is only made possible by the fact that it uses real liver cells (hepatocytes), and even then, it is not a permanent substitute for a liver.

On the other hand, Researchers Colin McGucklin, Professor of Regenerative Medicine at Newcastle University, and Nico Forraz, Senior Research Associate and Clinical Sciences Business Manager at Newcastle University, say that pieces of artificial liver could be used to repair livers injured in the next five years. These artificial livers could also be used outside the body in a manner analogous to the dialysis process used to keep alive patients whose kidneys have failed.^[2]

The researchers from Japan found that a mixture of human liver precursor cells (differentiated from human induced pluripotent stem cells (iPSCs)) and two other cell types can spontaneously form three-dimensional structures dubbed “liver buds.” In the mice, these liver buds formed functional connections with natural blood vessels and perform some liver-specific functions such as breaking down drugs in the bloodstream.^[3]

Lungs

With some almost fully functional, artificial lungs promise to be a great success in near future.^[4] An Ann Arbor company MC3 is currently working on this type of medical device.

Pancreas

Main article: Artificial pancreas

For the treatment of diabetes, numerous promising techniques are currently being developed, including some that incorporate donated living tissue housed in special materials to prevent the patient's immune system from killing the foreign live components.

Bladder

Main article: Artificial urinary bladder

The two main methods for replacing bladder function involve either redirecting urine flow or replacing the bladder in situ.^[5] Standard methods for replacing the bladder involve fashioning a bladder-like pouch from intestinal tissue.^[5] An alternative emerging method involves growing a bladder from cells taken from the patient and allowed to grow on a bladder-shaped scaffold.^[6]

Ovaries

Reproductive age patients who develop cancer often receive chemotherapy or radiation therapy which damages oocytes and leads to early menopause. An artificial human ovary has been developed at Brown University^[7] with self-assembled microtissues created using novel 3-D petri dish technology. The artificial ovary will be used for the purpose of in vitro maturation of immature oocytes and the development of a system to study the effect of environmental toxins on folliculogenesis.

Thymus

An implantable machine that performs the function of a thymus does not exist. However, researchers have been able to grow a thymus from reprogrammed fibroblasts. They expressed hope that the approach could one day replace or supplement neonatal thymus transplantation.^[8]

Trachea

Surgeons in Sweden performed the first implantation of a synthetic trachea in July 2011, for a 36-year-old patient who was suffering from cancer. Stem cells taken from the patient's hip were treated with growth factors and incubated on a plastic replica of his natural trachea.^[9]

Beyond restoration

It is also possible to construct and install an artificial organ to give its possessor abilities which are not naturally occurring. Research is proceeding, particularly in areas of vision, memory, and information processing, however this idea is still in its infancy.

Some current research focuses on restoring inoperative short-term memory in accident victims and lost access to long-term memory in dementia patients. Success here would lead to widespread interest in applications for persons whose memory is considered healthy to dramatically enhance their memory far beyond what can be achieved with mnemonic techniques. Given that our understanding of how living memory actually works is incomplete, it is unlikely this scenario will become reality in the near future.

One area of success was achieved in 2002 when a British Scientist, Kevin Warwick, had an array of 100 electrodes fired into his nervous system in order to link his nervous system into the internet. With this in place he carried out a series of experiments including extending his nervous system over the internet to control a robotic hand, a form of extended sensory input and the first direct electronic communication between the nervous systems of two humans.^[10]

Another idea with significant consequences is that of implanting a Language Translator for diplomatic and military applications. While machine translation does exist, it is presently neither good nor small enough to fulfill its promise.

This might also include the existing (and controversial when applied to humans) practice of implanting subcutaneous "chips" (integrated circuits) for identification and location purposes. An example of this is the RFID tags made by VeriChip Corporation.