dimanche 13 avril 2014

Bioprinting, Part 1: The Promise and the Pitfalls

A lire sur: http://www.technewsworld.com/edpick/80198.html

The technical side of printing small-volume organs "may be achieved within the next two years," said Kevin Healy, chair of the department of bioengineering at the University of California at Berkeley. However, the ability to develop vascularization of such organs is at least five years away. "The harder problem is to figure out what cells to use to avoid immune rejection."
's long been the dream of humans to be able to regenerate body parts. Scientists have been researching this possibility for years, but the subject is complex, and they are just beginning to get to a glimmer of understanding as to what's required.
"There are different layers of complexity in developing tissue-engineered products, so the easiest thing is to make it something that's one single type of cell and is a flat sheet," Charlie Whelan, healthcare and life science director of consulting atFrost & Sullivan, told TechNewsWorld.
Hospitals do grow single sheets of epithelial cells for use in patching burns and wounds or to wrap around organs, but that's a far cry from human skin, which is "multilayer, complex, has different types of cells, and is vascular," Whelan continued.

Step Aside, Gutenberg

In the meantime, the advent of 3D printers has opened up fresh possibilities.
Researchers at Edinburgh's Herriott-Watt University reportedly have invented a printer that creates living embryonic cells, according to LiveScience.
Bioengineers and physicians at Cornell University and Weill Cornell Medical College, respectively, have jointly created an artificial ear using 3D printing.
Researchers in China's Hangzhou Dianzi University claim to have developed a biomaterial 3D printer they call "Regenovo" that they say can print out small amounts of human tissues.
The U.S. National Aeronautics and Space Administration last year awarded US$100,000 for research into 3D printing of biomaterials.

All the Organs That Are Fit to Print

Many of the companies offering 3D biomaterial printers restrict themselves to printing out dental materials and bones.
Regenhu goes further. Its line of BioInk biomaterials can be used with its BioFactory bioprinters to create 3D constructs of cells and proteins, and complex models of organs for automated in-vitro assays for clinical diagnostics and drug discovery, and to create in-vitro models of human diseases.
The idea is to conduct biochemical tests on 3D tissues printed from a patient's own cells rather than on the patient, explained Jordan Miller, assistant professor of bioengineering at Rice University. "Right now, animal models can't fully predict drug toxicity and function in humans."
3D printing of skin will be readily translated to clinical use, but "3D printing of other tissues may take longer for clinical and commercial translation due to the fact that many other tissues have more complex structures," Roger Narayan, Ph.D., M.D., a professor in the joint biomedical engineering department at North Carolina State University and the University of North Carolina at Chapel Hill, told TechNewsWorld.
Narayan led a team from both universities and Laser Zentrum Hannover in research that discovered Vitamin B2, or riboflavin, can be used in 3D printing to create nontoxic medical implants.

Hope for the Hurt

Nearly 2 million people in the U.S. have lost at least one limb, according to the Amputee Coalition. About 185,000 amputations are conducted in the U.S. each year. Rejection of transplanted organs is the main problem for patients undergoing this procedure.
Bioengineered tissues may reduce the danger of tissue rejection following surgery, offer a higher rate of healing, and improve patients' chances of survival, Narayan said.
"The Department of Defense has committed significant resources over the years to the use of tissue engineering for treatment of traumatic injuries," Narayan continued. "3D printing-based and other tissue-engineering technologies will have a high impact on the treatment of traumatic injuries, as well as tissue loss associated with cancer and tissue degeneration."

The Blood Is the Life

Providing bioprinted organs a network of blood vessels so they can thrive has proved to be a major problem.
"Everyone in our field is trying to solve the vascularization challenge," Rice University's Miller told TechNewsWorld.
What about Regenovo, then?
"I would ... caution [against] taking the Regenovo report too far, and I wouldn't consider it all done," Miller remarked. "They admit they are still 10-20 years away from [developing] whole organs."

Other Issues With Bioprinting

The technical side of printing small-volume organs "may be achieved within the next two years," Kevin Healy, chair of the department of bioengineering at theUniversity of California at Berkeley, told TechNewsWorld. However, the ability to develop vascularization of such organs is at least five years away.
"The harder problem is to figure out what cells to use to avoid immune rejection," Healy continued.
Once this has been solved, researchers have to get donor cells and learn how to differentiate donor stem cells to the appropriate cells for the specific organ being printed.
"We know how to do this for a number of cell types, but, for a number of other cells like hepatocytes (liver cells), this is much more difficult," Healy pointed out.
Then there is the problem of nerve regeneration. Bioengineered products will require nerves, but "nerve regeneration is more difficult than blood vessel, soft tissue or hard tissue regeneration," Narayan said.

A Long Time A-Coming

"Parts of the body which require human cells to perform biomechanical functions, such as the liver or kidney, are still several decades away from reaching human patients," Miller said. "We are still in the feasibility stage -- not sure how to keep cells alive at high cell density and adequate size needed to match human organs."
A 3D structure will require nearly 1 billion functioning cells to approximate the function of a liver or kidney, and "there are dozens of cell types in these organs," Miller pointed out. "We are typically only looking at one or two cell types being put into a 3D printed structure."
It takes some time to grow enough cells from a biopsy to build something the size of a human organ, so the prospect of treating acute injuries with 3D printing is currently remote, Miller said. However, some researchers are looking at 3D printing a patient's cells and tissue directly into a wound in the operating room, though this would require having a "large stock" of these cells available in deep freeze.

Regeneration Is a No-Grow Zone

As for the dream of human limb and organ regeneration, forget about it.
"The cascade of signals and gene regulation which lets a newt regrow an entire limb was recently shown to not be present in the human genome," Miller observed. "So, for human limb replacements, we are probably going to need to think about reconstruction rather than stimulation of regrowth." 
"I worry about how well patients understand the risks associated with these new technologies," said the Baker Institute's Kirstin Matthews. Most patients in clinical trials believe that the intervention has a chance to help them, even though that typically is not the case. For 3D-printed technologies, "there will most likely be a lot of failure" before scientists get it right.
Nearly 120,000 people in the United States are on the waiting list for an organ transplant that may save their lives, according to the American Transplant Foundation.
"In the short term, we need many more people to register to be a potential organ donor," Jordan Miller, assistant professor of bioengineering at Rice University, told TechNewsWorld.
However, donor organs require immunosuppressive therapies, which can limit the recipient's quality of life, so over the long term, the medical community is "extremely excited about focused research funding to help progress 3D-printed organoids and organs for treating human patients."
The present thinking is that it will take decades to clear up the many technical problems that still have to be resolved before 3D-printed organs can be used for transplants. However, given that improvements in technology tend to follow a logarithmic rather than a linear pattern, the wait might be shorter.

What's the Right Thing to Do?

Research into using 3D printers to create human organs has given rise to a variety of moral and ethical questions.
The issue will trigger a major debate on ethics and regulation,Gartner has predicted, possibly sparking calls to ban the use of 3D printing for human and nonhuman use by 2016.

The Haves and the Have-Nots

Money, or the lack of it, will give rise to what might perhaps be the most pressing ethical concern.
Some of the new products could become cheaper and more accessible alternatives to current technology, but other products, such as functioning organs, which will be extremely complex to build or print, "will likely be only accessible to those willing to pay for personalized treatments," Kirstin Matthews, Fellow in Science and Technology Policy at Rice University's Baker Institute, told TechNewsWorld.
Patients who don't have the money "will be left on the organ transplant waiting lists," Matthews suggested, although that will depend on how much coverage the Affordable Care Act will provide.
If the new technology is more expensive [than existing treatments], it likely will not be added to healthcare coverage and therefore will be available only to the elite, Matthews said. "This will continue to expand the access divide between the haves and the have nots."

Biology vs. Technology

The cost of healthcare will lead to "a race between biology and technology," predicted Charlie Whelan, healthcare and life science director of consulting at Frost & Sullivan.
"Just because something works in the lab doesn't mean it will work in the marketplace, especially with the cost of healthcare," Whelan told TechNewsWorld.
An associated problem will be related to triage -- deciding, in essence, who deserves to receive the new technological treatments.
"We'll be in a situation where we'll have to decide whether, for example, we'll give an artificial kidney to an 80-year-old, who only has a few years to live and also needs an artificial heart," Whelan mused. "We have these thorny questions that I don't think we've had the need to deal with just yet because the technology isn't there."
However, this "hard economic calculus" already is being practiced when it comes to organ replacement therapy now, Whelan pointed out, so perhaps current best practices can be extended when the new technology finally is ready to use.

Being First Is Not Always Best

Another issue of concern is that the first patients to undergo transplants with 3D-printed organs will of necessity be desperate -- and because their doctors are breaking new ground, they will serve as guinea pigs.
"I worry about how well patients understand the risks associated with these new technologies," Rice University's Matthews said.
Most patients in clinical trials believe that the intervention has a chance to help them, even though that typically is not the case, Matthews remarked. For 3D-printed technologies, "there will most likely be a lot of failure before scientists discover the right methods, cells, techniques. Patients will have unreasonable expectations and might in fact be worse off after trying a new technology."

Rules and Regulations

There already are guidelines to handle patients being exposed to new medical technologies.
Hospital oversight boards would regulate donor issues, cells and tissue for informed consent, Kevin E. Healy, who chairs the department of bioengineering at UC Berkeley, told TechNewsWorld.
A magazine covering ethics in biology, engineering and medicine already exists.
The Biomedical Engineering Society approved a code of ethics back in 2004.
"Medical consent laws and medical ethics have come a long way since the days of Henrietta Lacks," Rice University's Miller said. "The FDA has strict safety and efficacy standards for implants made from a patient's own cells."

Beauties and Beasts

There might exist areas in which regulations and ethics may be ignored: illicit clinics catering to athletes and people seeking body modification for personal satisfaction or to gain an edge for themselves.
"It does not seem unreasonable to presume that individuals will try to find ways to enhance themselves with 3D printing if they can get an advantage," fretted Rice University's Matthews.
"Some athletes already assume significant risks to increase their performance on the field using illegal substances with serious side effects," she continued. "Others might seek enhancements to help achieve their ideal of beauty."
The federal government might not get involved in regulating cosmetic efforts, Matthews suggested. For athletes, organizing bodies such as the NCAA and NFL likely would be involved.

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