Bioprinting instead of donors?

Irina Tereshkova, Rosnauka

The technology of three–dimensional printing of organs - what seemed like something out of the realm of fiction yesterday, is now actively developing all over the world. Will we live to see the time when it will be possible to transplant a kidney or liver printed on a 3D bioprinter,"Rosnauka.ru " I found out from the specialists.

More recently, opponents of the idea of bioprinting argued that a human organ is an extremely complex mechanism, and it cannot be printed. Residents of Skolkovo, Russian scientists from the Laboratory of Biotechnological Research "3D Bioprinting Solutions", turned fantastic ideas into reality. They managed to print an entire organ on the first domestic bioprinter (experts call it an "organ construct") – the thyroid gland of a rodent. So far, no one in the world has been able to do this, despite the success of different countries in recreating individual fragments of human organs.

Laboratory specialists are constantly improving the technology of three–dimensional bioprinting, now they have to take an equally important step - to check how the construct will work. He will have a super-complex and responsible mission: to fully take over the main function of the thyroid gland – the production of the hormone thyroxine.

Here and below are photos of ZD Bioprinting Solutions

"We take mice and use radioactive iodine to turn off the function of the thyroid gland. To do this, we inject radioactive iodine into animals. It is known that the thyroid accumulates iodine, and after the injection it enters, first of all, into the thyroid gland. But since it is a radioactive isotope, it affects the gland: the thyroid tissue disintegrates, loses its functionality and ceases to produce enough thyroxine, which is called hypothyroid status," explained Elena Bulanova, head of the Laboratory of Cellular Technologies.

The rodent will be transplanted with a 3D-printed thyroid gland

Now experts have recorded a drop in the level of thyroxine in rodents – this is just the time when you can start transplant operations of the construct. The first conclusions can be made a couple of weeks after transplantation, when it becomes clear how well the thyroid gland takes root and whether the production of thyroxine increases. It will be possible to judge the successful course of the experiment no earlier than in a month and a half. 

"The operation is not very simple – the animals are very weakened after the injection of radioactive iodine. But we still really hope that they will undergo surgery normally, and thyroxine will approach its initial value. If the hormone level rises by 50% or higher, we will consider that this is a successful result," he said.Rosnauka.ru " Executive Director of the Laboratory of Biotechnological Research "3D Bioprinting Solutions" Youssef Hesuani.

The operation is also complicated by the fact that the surgeon will have to work with jeweler's precision in a tiny space: the organ construct itself is no larger than two millimeters in size. The miniature "seed" will be transplanted under the kidney capsule, this place was not chosen by chance: there the construct, already having a network of vessels, will be able to additionally receive new ones (nutrition of the organ construct). In addition, the kidney capsule will protect the tissue and prevent the body from rejecting foreign macromolecules.

How to print with live cells

The bioprinting process is practically the same as 3D printing technology made of plastic or iron, except that live cells are used here. You can print anything – from a pistol, an acoustic guitar and a car to a human organ.

The role of biochernils is performed by tissue spheroids – conglomerates of cells, bio-paper is a special hydrogel. In fact, the whole technology is a chain of strictly sequential actions.

Tissue spheroids, that is, special balls consisting of several hundred to several thousand cells, are obtained manually, the technique is well developed.

"We have a silicone stamp into which the straightened agarose is poured, then it freezes, and we get a negative in which there are 256 small depressions with a non-adhesive bottom to which nothing sticks. A cell suspension is poured there – a solution of cells. Under the influence of gravity, they settle to the bottom of the cells and, since they cannot stick to it, they begin to interact with each other, eventually forming one ball. As a result, 256 tissue spheroids are formed in one mold. Another method assumes that specialists pour the cell suspension into special dies, it also settles on one, forming one tissue spheroid in each cell," she said.Rosnauka.ru " senior researcher of the laboratory Elizaveta Kudan.

This is how tissue spheroids are obtained. After they mature, they can be loaded into a bioprinter and used as ink. 

Ink has a biological structure, it contains components of the extracellular matrix – this is the environment in which cells feel good and do not die. Choosing the optimal composition is an important task for biotechnologists. For example, in a solution of one alginate, which freezes easily and is necessary for the printing process, the cells will not die, but they will not be able to fuse, and the mobile and soft collagen will not allow the solution to thicken to the desired consistency, but it is necessary at the stage of cell fusion.

The domestic FABION bioprinter is subject to all existing methods of bioprinting, it is characterized by combinatoricity and multifunctionality, its important advantage is the polymerization system: there is no contact with cells, the beam affects only the layers of hydrogel – bio–paper.

Printing using spheroids is carried out according to the principle of extrusion, when the viscous consistency is forced through the forming hole: as from a pipette, gel or tissue spheroids are squeezed out of it. At the same time, at the time of extrusion, the hydrogel must be liquid, otherwise it will not be possible to squeeze it out, but at the same time, if it does not harden after hitting the bowl, a rigid shape for spheroids will not work. This is what the laboratory specialists are conjuring up, choosing the right temperature, concentration of components and pH so that everything goes according to the right scenario.

"For example, we have tried different approaches with collagen, it is known that all collagen-based gels harden when temperature and pH change. During the printing process, we do exactly this: we prepare the collagen gel in the cold, it already reaches room temperature in the printer, and at the same time during the printing process we spray sodium bicarbonate on it, which shifts the pH to the alkaline side. If we order some components, then we make collagen for the selection of printing conditions ourselves according to a proven method – from rat tails, which was invented in 1972, and it is still relevant," said Elena Bulanova, head of the Laboratory of Cellular Technologies.

After all the details are observed, the printer prints one layer of the organ, then another, and so gradually a whole organ construct is obtained in layers. Scientists do not set themselves the task of repeating the external outlines to the smallest detail, the main thing is to make sure that the construct can replace all the main functions of the lost organ.

Craftsmen of all trades

Like any new technology, the method of 3D printing of organs combines the achievements of many sciences, which is why the tasks of bioprinting are solved by specialists in multidisciplinary areas.

"Each employee of our laboratory has competencies and knowledge in several areas, we have collected unique ones. These are the piece specialists that we have been looking for all over the country and beyond. Now about 20 people work in the laboratory, including volunteers from the UK and Brazil," said Yulia Smirnova, Marketing Director of the 3D Bioprinting Solutions Biotechnological Research Laboratory.

Why did you choose the thyroid gland?

For such a large-scale scientific experiment, the choice fell on the thyroid gland for a reason. Specialists needed to take an organ that is relatively uncomplicated, does not have a branched duct system for removing the products of its activity, such as, for example, a kidney. 

According to the complexity of printing , all internal organs are divided into four types:

1. Flat organs (skin, cartilage) are the easiest to print, pieces of these organs are like "patches" on the human body.
2. Tubular organs (aorta, vascular bed): it is impossible to grow the entire aorta or vascular bed, only parts of the vessels are printed.
3. Hollow non-tubular organs (bladder, uterus). 
4. Solid organs (kidney, liver) are organs with a vascular bed consisting of several types of cells, for example, a kidney has 24 types of cells. 

The thyroid gland stands alone.

"The first and second groups, in the context of bioprinting, are only fragments of organs, "patches" on the human body, since it is impossible to print completely the skin or the entire vascular bed. To date, some scientists are already doing this, for example, in Japan or Canada. As for the third group, work is underway, but no serious progress has yet been achieved. The fourth group – the most complex organs – is the dream of all scientists. The thyroid gland, in our opinion, is the golden mean: on the one hand, it is an organ with an easily provable function, because it allows you to measure the level of hormones, which indicates the effectiveness of its work, on the other hand, it is not very complex in its structure. This is no longer a "patch", but also not such a complex solid organ as the liver or kidney," said Yusef Hesuani, executive director of the 3D Bioprinting Solutions Laboratory for Biotechnological Research.

By the way, it was the thyroid gland that was transplanted to a person for the first time in the history of transplantology. The laboratory specialists hope that they will be able to repeat this positive experience with an artificially grown construct.

3D printing instead of donors?

Jennifer Lewis from Harvard is working on the creation of a structural and functional unit of the kidney - the nephron, so we can assume that work on the reconstruction of the most complex group of organs has already begun. Well, then there is the seemingly impossible – the transplantation of printed organs to a person.

A well-known technological futurologist, and part-time technical director of Google, Ray Kurzweil, predicted that already in 2031, 3D printers will be installed in all hospitals and organs will be printed for everyone in need. Experts in the field of bioprinting are not so categorical and ask not to hurry: in their opinion, by 2030, technologies will allow printing only the first solid organ, and only some scientists claim that they will be able to do it earlier.

"70-80% of the needs are kidneys, we set ourselves such a hyper–goal. Now the laboratory is working on three-dimensional printing of the thyroid gland, flat and tubular organs, as well as on the modification of the printer. At the same time, what we are doing today may be useful to us for solving more complex tasks tomorrow. In the future, bioprinting can solve the issue that is open all over the world – the shortage of donor organs, this is its global goal," Youssef Hesuani believes.

You can use bioprinting technologies without waiting for this bright future. Printed three-dimensional biostructures are already helping pharmaceutical companies to test new drugs. Cells in a three-dimensional structure make it possible to achieve greater accuracy of research and save effort, time and money at the preclinical testing stage.

Bioprinting is also beginning to be used in areas not related to medicine, for example, in the world of fashion and gastronomy. Experts promise that it will soon be possible to create a steak or fur for a fur coat using 3D technologies. The first such experiments, which, by the way, are very supportive of the "greens", already exist.

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23.07.2015