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> An Introduction to Tissue Engineering
This article provides a brief introduction to tissue engineering, the process by which organs can be grown artificially. It covers the problems with organ transplants, the tissue engineering process, and the current successes and problems of the technology.
The current treatment for organ failure is organ transplantation, taking an organ from a living or deceased donor and transplanting it into a patient. However, there are problems with this operation. For one, there are more people waiting for an organ than there are organ donors. Currently, there are over 123,000 people on the waiting list with just under 12,000 donors available. Clearly, supply does not meet demand. Another issue is that not all organs are a match to the patient. Organs need to correspond to a patient’s blood and tissue type in order for the body to even have a chance at accepting it. Even then, that patient may need lifelong immunosuppressive therapy (which can lead to diabetes, hypertension, and renal failure) to keep their immune system from attacking the organ. Because of these complications in organ transplants, an average of 18 people die each day from organ failure. However, scientists are developing a new technology that could meet organ demands and correct the issues of organ transplants: tissue engineering.
What is Tissue Engineering?
Tissue engineering is the process by which an organ or tissue is created from a person’s own stem cells – simple, undifferentiated cells that can develop into various other types, including heart, lung, and blood cells. In order to begin the process, scientists may first scan the patient’s organ in order to create a replacement of the exact size and shape. Next, a three-dimensional scaffold is created to act as a mold for the new cells’ growth. There are two common ways to create the scaffold. The first involves a 3D printer, which generates a scaffold based on an intricate computer model. The other involves putting the original organ through the decellularization process. In this procedure, the organ is submerged in detergent for 3 to 4 days in order to rinse it of all cells, leaving a scaffold made of the organ’s own proteins. Only when the scaffold is ready is it covered in the patient’s donated stem cells and placed in a bioreactor. This machine has the capabilities to provide the correct amount of nutrients, oxygen, and chemicals needed to stimulate the cells’ growth. After a few weeks of growth, the organ is ready for transplantation, and because it is made of the donor’s
own cells, there is no fear of rejection.
Although the field was created in the 1980s, important advancements in tissue engineering have not been made until more recently. For example, in 1999, Dr. Anthony Atala, a physician at the Wake Forest School of Medicine in North Carolina who had been working on growing organs from cells since 1990, grew the first artificial bladder (the long-term success of which was reported in 2006). By 2011, this technology had evolved enough for a Swedish man to be given a replacement windpipe. The most recent and, arguably, most important innovations in tissue engineering involve work with mice. In 2013, scientists used human stem cells to replace failing livers in mice. These “liver buds” continued to grow after transplantation and took on functions of a normal liver, including the jobs of secreting proteins and producing human-specific metabolites. Finally, in 2014, experts reprogrammed mice embryo cells called “fibroblasts” to form and act as a thymus, a small organ central to the immune system.
Such advancements, however, come with drawbacks. Growing artificial organs is a recent technology and, as a result, has not improved enough to create fully functioning versions of advanced organs. One such example, the kidney, is needed by about 80% of those on the waiting list. This solid organ is composed of more complex cell subtypes and more blood vessels compared to a windpipe or bladder. Another difficulty is that different cell types need different chemical and environmental cues and physical forces in order to multiply – many of which are difficult to replicate in a laboratory. Lastly, the process of tissue engineering is expensive, so the vast majority of those in need of the organs are unable to afford it.
Although tissue engineering needs to improve, it has advanced a large amount in a short amount of time. Hopefully, scientists will be able to replicate all organs for a low cost and save more lives.
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