Regenerative medicine
Regenerative medicine is a field focused on repairing or replacing tissues and organs damaged by disease, injury, or congenital conditions. It encompasses a range of approaches, including organ transplantation, artificial organs, and bioengineered tissues created from stem cells. As the demand for donor organs has outpaced supply, researchers have explored innovative methods to manufacture substitutes, such as growing replacement bladders using a patient’s own cells and biodegradable scaffolding. This technique leverages the extracellular matrix, which supports cell structure and function, to cultivate new tissues.
Stem cells, which can differentiate into various cell types, play a vital role in this area, although their use can be controversial due to ethical concerns surrounding their sources. Advances in regenerative medicine also include the potential use of animal tissues for human applications and 3D printing technologies that promise customizable organ creation. With ongoing research and development, regenerative medicine holds the potential to treat a wide array of conditions, including chronic diseases and injuries, significantly improving patient outcomes and quality of life.
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Regenerative medicine
Regenerative medicine refers to procedures that replace tissues or organs that have been damaged by disease or injury or that are malfunctioning due to congenital conditions. In its broadest definition, regenerative medicine refers to replacing organs or tissue with transplanted substitutes. These can be organic replacements from donors, artificial organs, or medical devices such as artificial heart valves. However, some experts prefer to limit the term regenerative medicine to bioengineered tissues and materials that are grown or formed in laboratories or within the body from organic material such as stem cells. New breakthroughs in this type of medicine could help eliminate loss of life caused by a shortage of donor organs and create new ways to replace body parts for which transplants are not a reliable option.
Background
In its most general form, regenerative medicine is more than a century old. The first successful human-to-human transplant was performed on December 7, 1905, when Austrian ophthalmologist Eduard Zirm successfully transplanted a cornea from an eleven-year-old boy to a forty-three-year-old man.
The first successful kidney transplant in 1954 opened the door for more organ transplants as physicians applied the techniques learned from that operation to other organ surgeries. In the following decade, physicians were able to complete successful transplants of pancreases, kidneys, livers, and hearts. By the 1980s, single- and double-lung transplants, dual heart/lung transplants, and living donor liver and lung transplants were possible.
The improved ability to transplant organs created a problem, however. As physicians gained the ability to treat more conditions with transplants, the demand for donor organs increased but the supply did not keep pace. By the early part of the twenty-first century, physicians were performing about half a million transplants in the United States alone. At any given time, nearly 110,000 people are on a transplant waiting list, and many die before replacement organs become available.
To help counter this problem, researchers began looking for ways to manufacture substitutes for human donor organs. The earliest efforts in the 1990s were with human bladders. Using cells from the patient, researchers found a way to grow replacement bladders. They did this by taking muscle and tissue samples from the patient's bladder and growing them in a laboratory until they reproduced enough cells to begin forming a new organ.
The researchers placed the cells on a bladder-shaped form made of biodegradable materials. Once the cells covered the form, it was implanted in the patient and stitched to the malfunctioning bladder. As the new bladder integrated into the body, the biodegradable scaffold on which it was formed was absorbed, and the newly created bladder was left in its place. This was successfully accomplished for the first time in 1999. Following this success, researchers began work on finding ways to grow other types of tissue and organs.
Overview
Bladders grown from patient cells are examples of tissue engineering and biomaterial. This relatively new technique has been used to generate many types of organs and tissues, and it has the potential to produce many others. This is possible because of a part of the cell known as the extracellular matrix, or ECM. The ECM is not part of the functioning cell but serves as a support system. It helps provide structure for cells and anchors them together. The ECM also helps cells find their correct places when the organism in which they are located is growing or repairing itself, and it sends out signals that tell cells when to reproduce, what kind of cell to become, and when it is time for individual cells to die. Researchers have found ways to use these properties of the ECM to grow new cells and even new organs. They are also working on additional ways to apply what they know to growing new types of organs.
Another way new body parts can be grown involves stem cells. Stem cells are known as undifferentiated cells. This means that they are capable of becoming different types of cells depending on what signals they receive during their formation and growth. Stem cells are sometimes harvested from young embryos; this practice can be controversial, as many of these embryos are the result of unwanted in vitro fertilization attempts or aborted pregnancies. Stem cells can also be found in adult bodies, and they can be reprogrammed to become other types of tissue. For example, skin cells can be reprogrammed to grow other types of tissue.
Physicians have also used animal tissue to replace human tissue. A product known as small intestine submucosa, or SIS, is derived from pig intestines. It is used for wound treatments, and it can replace some ligaments in the human body. Similarly, goat stem cells have been used to help repair damaged knee cartilage. Additional efforts are underway to find ways to use animal tissue to help replace or repair human body parts.
Other techniques are being researched as well. Scientists have successfully grown a human ear using human cells over a scaffold carved from an apple slice. This technique both replaces more expensive bioengineered scaffolding material and makes nearly any body part replicable since fruits such as apples can be easily shaped. Researchers have also found ways to put a liquid tissue matrix into an ink cartridge for an inkjet printer. With three-dimensional printing techniques, researchers hope to be able to design and print organs that can be customized to any shape or size.
The field of regenerative medicine is growing almost daily. It may eventually be possible to replace nearly any organ that has become diseased or damaged. Researchers are also working on techniques that would allow a physician to implant replacement cells into an aging or worn out organ to allow it to regenerate to its full function. There is increased interest in using the technology of regenerative medicine to help those who suffer disfiguring burns or lose limbs as the result of war or terrorism. Researchers are also searching for ways to use regenerative medicine to put an end to chronic health conditions such as diabetes, kidney disease, and heart disease.
Bibliography
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