Following is an in-depth exploration of tissue engineering.

Tissue engineering is a method of creating, maintaining or restoring tissues or organs. It is an interdisciplinary field using principles of engineering and life sciences. Typically cells from a biopsy are replicated in great numbers then placed on a scaffold (form) of the body part to be created. The newly created body part is then transplanted into the patient.

The first patients to receive Atala's regenerated organs were seven young children who were transplanted with bladders grown from their own cells. Eight years after their surgery, the children are doing well, and their bladders continue to function normally.

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"Such an approach [tissue engineering] has already been used successfully for the repair and reconstruction of complex tissues such as the trachea, esophagus, and skeletal muscle in animal models and human beings," Professor Macchiarini said.

,,,,,in 2010, a British team assisted by Professor Macchiarini performed a similar operation on a 10-year-old boy, who had been born with a narrow windpipe. In his case the donor trachea was transplanted into his chest as soon as it had been reseeded with stem cells taken from his bone marrow, using his own body as the bioreactor……

....."Guided by appropriate scientific and ethical oversight, [this] could serve as a platform for the engineering of whole organs and other tissues, and might become a viable and practical future therapeutic approach to meet demand after organ failure," he added.

Biomedical engineers have developed lab-grown skeletal muscles that can flex as strongly as the natural-born items, work the way they're supposed to when they're implanted in mice — and even heal themselves if they're hurt.

"The muscle we have made represents an important advance for the field," Duke University's Nenad Bursac said in a news release about the project. "It's the first time engineered muscle has been created that contracts as strongly as native neonatal skeletal muscle."…..

Now the team is looking into whether lab-grown muscles can be used to repair actual muscle injuries and diseases [in humans]. "Can it vascularize, innervate and repair the damaged muscle's function?" Bursac asked. "That is what we will be working on for the next several years."

Achieving vascularization may be the biggest challenge that faces researchers attempting to 3-D print organs, but 3-D printing could also be the very technology to solve this problem. Researchers are harnessing 3-D printers to build tiny, hierarchical networks of blood vessels to supply increasingly complex 3-D–printed organs with blood…..

“For me the holy grail of tissue engineering is to fabricate tissues with their own vascular network,� says Jason Spector, an associate professor of plastic surgery at Weill Cornell Medical College, who is working on printing ears and other tissues. “Once you can make that, everything else is cake.�…..

Numerous other groups are also trying their hand at 3-D printing of vasculature, and should any of them prove successful, it would pave the way for tissue engineering on a grander scale than ever before. Growing and implanting larger swaths of bone or skin may become feasible, and producing more-complex organs like hearts or kidneys might become more realistic. …..

“It’s just a really fun technology,� says Miller. “We’ve made thousands of these structures and every time they print it’s just magic.�…..

3-D printing allows tissue engineers to fabricate more-complex shapes and to more precisely mix materials than does the process of growing organs by seeding cells onto handmade scaffolds.

Anthony Atala—whose artificial bladders, made by growing a patient’s own urothelial and muscle cells on collagen and polyglycolic acid (PGA) scaffolds, are now in clinical trials—says he is working on bioprinting a multitude of tissues and organs, including muscles, bones, tracheas, ears, noses, and kidneys. His goal is to design bioprinters that can print usable engineered tissues at all levels of complexity. Many other researchers are also forging ahead with 3-D printing projects that may reach patients in the near future.