Foreign media: 3D technology or in the future can "print" human organs

It is one of the primary goals of regenerative medicine to build human organs from scratch, as in the case of manufacturing a component, a crash and no risk of rejection, foreign media said. Now scientists are focusing on 3D printing. With the development of science and technology, human life is growing longer, and the result is that human organs have never worked so long, according to a September article in the Spanish Journal of Fun. In the European Union, 9 people die every day while awaiting transplants.

"The number of patients needing organ transplants has doubled in the last 10 years," said Anthony Atala, director of the School of Regenerative Medicine at Veckforest University in the United States. While more and more organ donors are still unable to meet the growing demand. "The most promising method at the moment is to replicate human organs, but this is a common practice in dental hospitals."

Atala has spent more than 30 years in this area of research. In the past it has been a relatively simple muscle and blood vessel, but in early 2014 Atala announced a leap-forward study: 4 Laboratory artificial vaginal transplants have been successful. Today, after 8 years of implantation, 4 patients with congenital diseases can finally enjoy a normal sex life.

In order to create human organs from scratch, scientists first need to be able to become any human tissue stem cells, the article said. Until recently, the only way to get stem cells from human embryos was to raise ethical arguments. But now we can get stem cells without creating embryos.

For example, the process is like a time machine. After culturing a patient's cell sample in the laboratory, the process of maturation was reversed through external intervention. The cells are "rejuvenated", reversing the stem cells that can breed new embryos. But how do new tissues or organs form?

The answer is: formed by the support of the growth bracket. The scaffold is made of porous polymers, a biocompatible and biodegradable scaffold that allows cells to continue to grow and form different tissues until an ideal organ shape is obtained. "It works like a prosthetic limb," says Atala. If you enter information obtained through X-ray photography and scanning, the 3D printer can accurately replicate the patient's organs. ”

The second step is to thinly cover the cells of the patient in advance. Finally, cells in the growing process need to reach maturity in a bioreactor. Intelligent bioreactor can simulate the environmental conditions in human body. Artificial organs will continue to grow until they are implanted in the human body until they are perfectly similar to the innate organs.

For those who are waiting to donate their organs, being fortunate enough to donate a liver or kidney is a new birth. However, even if the donor's heart is transplanted, the recipient may suffer from rejection. "If you take advantage of the patient's own cells, there is no such problem," says Atala. ”

Another advantage of artificial organs is that they greatly shorten the waiting time. Thanks to this, patients can transplant artificial organs early in the disease, which is relatively healthy and easier to recover from after surgery.

The manufacture of scaffolds with biocompatibility is a subject that is still in the process of research and development. Whether the artificial organs can be transplanted successfully, the timing and control is the key. Because if the stent is degraded early, it will be too delicate to support cells to form the ideal organ shape. Similarly, if the stent is degraded too slowly, the area of the implanted artificial organs and the surrounding tissues will form scars that affect the normal functioning of future artificial organs.

One way to solve the problem is to reclaim the donor organ that does not match the receptor and to make it cellular. A study group at the University of the Goethe-Institut in Sweden in 2012 first successfully transplanted a venous vessel using a biological scaffold, which was made from a body's blood vessels.

As with all organizations, the process is to use the removal agent to cell the donor's organs. This leaves only the protein structure that determines the shape of the tissue. Experts point out that, from a theoretical point of view, this reasoning is unassailable because there are superfluous organs that can be reused as scaffolds. The School of Regenerative Medicine at Veckforest University has confirmed that the theory can be applied to pigs ' kidneys.

In any case, the best alternative to avoiding the potential problems of polymer stents is to create organs without stents, so that 3D printing technology attracts everyone's attention. Organovo, the American biotech company, has put the printed liver tissue into the market.

The paper says the process requires a sophisticated analysis of the organization's institutions and translates it into code that the printer can identify. Organovo's experts use the body's cells, living cells in the petri dish, or cell strains to make the bio ink in the cartridge. Liver samples continued to proliferate, die and be replaced by living tissue during their 1.5-month survival period. They help to test the toxicity and efficacy of drugs before they are put into clinical trials.

Atala and its research team are also developing 3D printing technology at the School of Regenerative medicine at Veckforest University. In addition to trying to make biological scaffolds using cells rather than polymers through 3D technology, Atala also hopes to develop micro-organs. "We want to be able to print out the heart, lungs and liver proportionally and replace the animals in the lab," he said. These artificial organs are equipped with chips and can be used to survive with a blood substitute. ”

"We plan to create a complete organ in the future," said Keith Melfi, executive director of Organovo company. He added: "However, we prefer to be able to produce smaller organizations." For example, we can use the cells of the patient to print out patches to repair the heart of the infarct, which avoids rejection. ”

A new study by the University of Iowa in the United States suggests other uses for mini organs. For example, the pancreas is made up of two kinds of cells, but only 2% of the insulin-secreting function. Selecting useful cells to produce tissue can provide insulin to diabetics without having to produce a complete pancreas. In addition, micro-organs can also enable the body to have new functions. For example, if you create an organ that generates electricity, you don't need to have a battery in your pacemaker.

If you insist on printing a fully living organ of the same size as the natural one, the biggest challenge is to create an effective vascular system. In the human body, the blood flowing through the meridians, arteries and capillaries undertakes the role of conveying nutrients and cleaning waste. But in man-made organizations, these mechanisms do not exist. So there's no way to print a cell layer that's thicker than a few microns. "Our vaginal and tracheal transplants have been successful because they are delicate enough without the need for blood vessels to penetrate," says Atala. ”

Some man-made tissues, such as the Organovo company's liver tissue samples, have embryonic forms of angiogenesis, but it is not realistic to make complex vascular networks at the same time.

Experts at the School of Regenerative medicine at Veckforest University are working on the development of artificial vascular systems. "We now have two options: using vascular endothelial cells to make small blood vessels, or using oxygen-producing materials to make stents," says Atala. ”

The Harvard Institute of Biotechnology has the world's highest-definition 3D printer, capable of producing micro-tissue, including human capillaries.

While printing blood vessels, the researchers doped living cells and extracellular matrix into a particular biological material. Ordinary biomaterials harden when cooled, and this particular polymer melts gradually as temperatures drop, releasing non-productive cells and extracellular matrix. After the formation of artificial vascular tissue, these cells can stay in the original tissue position, and useless surplus material will be sucked out.

The researchers used the technique to create tissue from 3 of cells and complete vascular systems. In addition, they cultured vascular endothelial cells on the nascent vascular network to cover blood vessels.

This is a feasible and fast method, but also save the cost. The University of Pennsylvania has developed a similar technology that, while less efficient and more accurate than Harvard's, uses carbohydrates instead of special biomaterials. In other words, use sugars as ink for the 3D printer. The technology was inspired by the fine structure of the marshmallow, the researchers said. As a result, excess material can be removed with water.

In addition, researchers have been inspired by the world's first self-replicating printer. This 3D printer, called RepRap, is free and open source for everything from software to hardware, and anyone can make a printer like this and then use it to print out parts that are exactly the same as the printer.

There is still a long way to go before the challenges of the vascular system are breached. The next challenge is that many of the cells in the man-made tissue cannot survive the printing process. Therefore, it will take some time for the distance to integrate the printing technology into the daily life. But let us not forget that, more than 10 years ago, the pioneer of digital 3D Printing said that the future 3D printers capable of printing organs would be as common as the electronic microscope that was born in the 1930s.

(Responsible editor: Mengyishan)