Tissue Engineering Essay, Research Paper
Benefits of Tissue Engineering Every day thousands of people of all ages are admitted to hospitals because of the malfunction of some vital organ. Due to the shortage of transplantable organs, many of these people will die. In perhaps the most dramatic example, the American Heart Association reports only 2,300 of the 40,000 Americans who needed a new heart in 1997 got one. Lifesaving livers and kidneys likewise are scarce, as skin is for burn victims and others with wounds that fail to heal. Imagine a day when people with liver failure can be cured with implanted “neo-organs” made of liver cells and plastic fibers or when insulin-dependent diabetics can forget their frequent insulin injections because they have semisynthetic replacement pancreases. Sound like science fiction? Not to scientists working in tissue engineering, a field of science that is barely a decade old. Over the past ten years, tissue engineering has evolved from a jumble of different disciplines to a biotechnology field in its own right. A marriage of chemical engineering and cell biology, with input from genetics and surgery, tissue engineering combines living cells, biochemicals, and synthetic materials into implants that can function in the human body. Tissue engineering involves the use of cells and the extracellular components, either natural or synthetic, to develop implantable parts for the restoration, maintenance, or replacement of function (Introduction, 1). In one scenario, a tissue engineer injects a given molecule, such as a growth factor, into a wound or organ that requires regeneration. These molecules cause the patient s own cells to migrate into the wound site, turn into the right type of cell and regenerate the tissue. In the second procedure, the patient receives cells that have been harvested and incorporated into three-dimensional scaffolds of biodegradable polymers. The entire structure of cells and scaffolding is transplanted into the wound site, where the cells replicate and reorganize to form new tissue. At the same time the artificial polymers breakdown, leaving a completely natural final product in the body a neo organ. Tissue engineering may revolutionize the treatment of patients who need vital structures; it is a potential solution to the lack of transplantable organs.One impact that doctors argue is that tissue engineering will have a helpful impact on promoting the healing of wounds and repairing damaged organs by using growth factors. Scientists, like Dr. Eaglstein, M.D., chairman of the department of dermatology at the University of Miami School of Medicine, are anxious to see what tissue engineering is going to do for the six million patients with chronic wounds wounds that won t heal. These wounds that cannot heal properly include: burns, pressure sores, typically found on the buttocks and hip areas among people confined to bed or a wheelchair; diabetic ulcers, usually found on a foot or toe and often a result of constant rubbing not detected by the patient because of a loss of feeling in the foot or toe; and venus ulcers, usually occurring on the leg and caused by a lack of organized blood flow back to the heart. (Mother Nature, 1). US nursing homes suggest that 20% of patients suffer from pressure sores (decubitus ulcers), and it s estimated that treatment costs $3 billion. The cost of treatment per year for diabetic ulcers are $16-21 billion and that the costs of amputation are $1.5 billion (MDL, 2). Fibrogen, a research company in treating wounds with growth factors, estimates that 800,000 patients in the U.S. are hospitalized annually with severe bone fractures. Many of these fractures do not mend properly requiring supplemental procedures, such as bone grafts, and other fractures are non-responsive to any effort. These wounds are clearly a major economic problem. Physicians are now looking to tissue engineering as a way to cut cost; time, pain and repair damaged tissue where yesterday s technology could not. Various clinical trials are under way to test different bone growth promoters to regenerate bony tissue. One method, developed by Creative BioMolecules, show that BMP-7 (bone morphogenetic proteins), a growth factor, does heal a severe leg fractures. In one case a leg fracture, which did not heal after nine months, was introduced to BMP-7. The patient whose leg was encouraged by the growth factor healed just as well as a person who received a surgical graft (Scientific, 3). Limited joint mobility and poor cosmetic outcome are two of the major drawbacks associated with current therapeutic approaches to the repair of burn wounds. Tissue engineered LifeCell is a cell-seeded allogenic skin replacement for burn victims. It is made of human dermal collagen seeded with allogenic fibroblasts. The material is an alternative to painful skingrafts and skin taken from cadavers. As for the chronic wounds there are many syntactic materials now ready to be used, such as Dermagraft (manufactured by Advanced Tissue Sciences). Results from a recent clinical study examining Graftskin (a skin substitute) treated venous stasis ulcers show that at 90 days post-treatment, 70% of Graftskin-treated patients were completely healed, compared to 28% successful healings used by previous methods, such as skin grafts. There is little doubt that tissue engineered approaches to wound repair will present significant therapeutic benefits when compared to existing treatments. Tissue engineered materials will increased potential for healing of recalcitrant lesions, reduce wound scarring, and reduce treatment costs and hospital stay. Tissue engineering may well revolutionize medicine over the next ten to 15 years, reshaping the $40-billion-a-year medical implant industry just as biotech is transforming the drug business (MDL, 1-5).Another argument is that through tissue engineering mechanical organs and prosthetics can replaced by lab grown organs. As the human life span increases there is a need to prolong the productivity of our organs. The aging process rarely takes the same toll on all our parts, and often a critical organ like the heart gives out long before others do. Besides growing old, accidents, disease and cancer can destroy organs and other body parts. The best hope in such cases is to replace the decayed part with an organ transplant or mechanical prosthetic. But prosthetics pose many obstacles. For example, the device must be compatible in size to that of a natural organ. The size becomes a constraint because the device must be able to required to perform the function desired. These devices also need to be compact and receive as little attention as possible from the public so that the patients can feel normal. Another hopeful application of tissue engineering is the creation of kidneys to replace dialysis machines. Normal functional kidneys regulate the chemical balance of blood; they prevent build up of toxins. But more than 20,000 Americans are dependent on machines to process their blood for them. Dialysis is the artificial way remove waste and excess fluids from the body. Patients have to spend up to four hours three times a week at clinics hooked up to dialysis machines (Dialysis, 1-6). Scientists hope to one day create synthetic kidneys to replace the need of dialysis. This would free up the time a patient has to spend getting their blood cleaned by a machine. It would be a perfect cure to kidney failure. Tissue engineering is also a potential answer for accident victims. In an industrial accident Raul Mercia lost his thumb tip. Physicians from UMASS Medical School harvested samples of Mercia s bone cells and used them to regenerate the patient s thumb segment. Dr. Shufflebarger, of UMass, said, doctors carved medically sterile coral into the shape of the original thumb bone to serve as a scaffolding to support the engineered cells. The cells, suspended in an inert gel, were then seeded onto the coral and are expected to grow to form new functional bone (Surgeons, 1). The technique was pioneered by the chairman of the department of anesthesiology at the University of Massachusetts Medical Center, Charles A. Vacanti, who already has grown an ear from human cartilage cells. He also has grown tracheas, ligaments, tendons and bone. The potential clinical applications of Vacanti s tissue engineering technology are being considered for breast surgery. He is attempting to use tissue from the legs or buttocks to grow new breast tissue, to replace that removed in mastectomies or lumpectomies. Vacanti proposes to take a biopsy of the patient’s tissue, isolate cells from this biopsy and multiply these cells outside the body. The woman’s own cells would then be returned to her in a biodegradable polymer matrix. Back in the body, cell growth and the deterioration of the matrix would lead to the formation of completely new, natural tissue (Scientific, 6). This process would create only a soft-tissue mass, not the complex system of numerous cell types that makes up a true breast. Nevertheless, it could provide an alternative to current breast prostheses or implants. All these different applications would not only work better than today s mechanical organs and prosthetics but they would also provide their users with new confidence in their appearance. Through tissue engineering patients can gain new limbs and organs which will make them feel and appear more whole.
The third argument is that tissue engineers hope patients in need of organs with neo-organs grown from their own or someone else s cells. The U.S. Health and Human Services Department estimated that 4,000 people die each year awaiting organ transplants. In today s world, 30,000 people die from liver failure. The need to find an abundant supply of organs is dire. But the ability to stockpile a library of pre-grown organs is not a far away dream any more.Recently Dr. Anthony Atala of the Harvard Medical School and his team grew fully functioning bladders, which were then successfully transplanted into dogs. The bladder consists of three layers — a muscle layer, a matrix, and a layer on the inside made up of special urothelial cells. The doctors took small amounts of bladder tissue from the six dogs and then multiplied in an incubator. To make a whole bladder structure from sheets of tissue, the team designed a bladder-shaped polymer matrix mold that would biodegrade in the body over time. On that scaffolding they constructed a “bladder sandwich,” seeding the polymer matrix with successive layers of muscle cells on one side and urothelial cells on the other. The final organs were then placed into the original dogs. And after 11 months, these bladders were filling, emptying, and stretching elastically like a normal bladder. These same techniques are hoped to be applied to human bladders for the 400 million people worldwide suffer from bladder disease, internationally (Lab,1-3). Dr. Laura Niklason of Duke University and her team of researchers achieved another advancement in tissue engineering. Working with pig cells they have grown living arteries.Niklason took a sample of smooth muscle cells from a neck artery in the pig and then bathed it in cell nutrients and oxygen. The cells multiplied and grew on a polymer tube that acts as a scaffold for the growing artery and later would dissolve. After only ten weeks smooth muscle cells had replaced the tube, which was later lined with endothelial cells to complete the artery. The arteries created were then placed back into the original pig donors; their bodies accepted them without any problems. Many patients with narrowed heart arteries undergo heart-bypass surgery, in which a portion of a healthy blood vessel often a leg vein is implanted into the heart-artery network so blood can detour around a blockage. If these transplanted veins form their own blockages, however, patients must go through bypass again. Ultimately, if these arteries work for patients with more severe disease, the vessels may play a larger role in bypass surgery. Even when patients own vessels can be used, Niklason explained, a leg vein is not the optimal substitute for a heart artery (Researchers, 1-4). When neo-organs are placed into the original donors whose cells were used to grow the new organs there is no chance for the body to reject it. Both cases show that growing organs from cells is possible. Another recent technique recently discovered to grow organs is by using human stem cells. Stem cells are the foundation of all other cells. By knowing how to manipulate them, doctors can build virtually any other tissue. However, many people feel that using the stem cells is unethical because of where they come from. Stem cells are taken from discarded fetal tissue, miscarriages and abortions. Embryonic stem cells can only be identified and cultured after an embryo has developed for a few cell divisions (ABCNEWS, 1-3). For some this means that a new human being, a new person exists. But for others, embryos are not human beings, just potential ones, and thus have no moral standing. Activists feel that a new demand for fetal tissue and incentives will be caused by research on stem cells. Even if embryo are considered a person, the promises that the therapies from embryonic stem cells hold for those who are paralyzed, burned, dying of liver and pancreas failure, brain injured and suffering from many, many other diseases and injuries must be considered (Sprouting, 1-5). Even though there has been much advancement in the tissue-engineering field, experts feel that their benefits will not be used in today s market for many years. Mikos believes that substitute skins will be available for most medical uses in the next three years. As for the lab grown livers and hearts they are not expected to hit the market for the next two decades (Scientific, 6-8). Tissue engineering is the potential answer to many health problems. This industry may make organ donation unnecessary and prosthetics pointless. Maybe in the future getting a new kidney will be as easy as going to Blockbuster Video and picking out a movie. No one is quit sure of where the future is headed, only that it is coming.