Unveiling the secrets of living organ bioprinters: Printing veins with cells

According to Wired magazine, organ transplantation has saved many lives, but this technology also has drawbacks such as insufficient organ sources and difficult-to-avoid rejection reactions. Now, with the development of a bioprinter by Organovo, a US biotechnology company, which can "print" veins using the patient's own cells, these problems will be solved. Perhaps one day, doctors will be able to "print" living organs on demand, including blood vessels and complete organs.

"We are literally printing blood vessels right now," said Ben Shepherd, a senior scientist at Organovo. "We printed quite a few this week and are also learning how to maximize their functionality so that we can print more reliable blood vessels." Most organs in the human body are densely packed with veins, so the ability to print vascular tissue is a key step in obtaining complete organs.

The printed veins are about to begin testing on animals and eventually on humans. If all goes well, in a few years you might be able to replace veins that have gone bad, such as those deteriorating from frequent chemotherapy injections, with “printed” tissue grown from your own cells. Printing entire organs doesn’t just face technical hurdles: The first organ bioprinter will cost hundreds of millions of dollars to develop, test, produce and bring to market, not to mention the difficulties any company will face in getting approval from the U.S. Food and Drug Administration.

"If Organovo can raise enough funding, it has the potential to succeed as the first bioprinting company, but it will take time to prove it," said Dr. Vladimir Mironov, director of the Center for Advanced Tissue Biomanufacturing at the Medical University of South Carolina. Here's a look at the entire bioprinting vein process demonstrated by Organovo.

1. Bioreactor

Sheppard places a bioreactor in an incubator, reacts it with growth media, and removes it a few days later. The bioreactor uses a special chemical cocktail that helps the cells become strong vascular tissue, similar to what happens when the cells grow in the human body.

2. Stem Cells

Sheppard removes the stem cells from the pool of liquid nitrogen. After being cultured, the number of stem cells will increase rapidly and then be injected into the bioprinter. Eventually, these cells can be taken from various parts of the patient's body - fat, bone marrow and skin cells - to make functioning veins. After the stem cells are thawed, they will be cultured in a growth medium. This step allows the stem cells to continue to multiply and grow so that they can be used to form veins. The growth medium also uses special chemicals to make the stem cells grow into the desired type, in this case, blood vessel cells. Once enough cells are made, they can be separated from the growth medium using a centrifuge and compressed into pellets.

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3. Hydrogel Scaffold

The first step in the bioprinting process is to lay down a material called a hydrogel, which acts as a temporary scaffold to support the vein tissue. The custom bioprinter ejects the scaffold structure or cells into a culture dish through two pump heads. The pump heads are mounted on a high-precision robotic assembly instrument to maximize accuracy. In the photo above, the pump head on the right is immersed in a container of hydrogel.

A small container called a bioreactor is used to simulate the vein, and it is prepared before the vein is printed. The bioreactor is a fairly standard part of the biotech system, made from a piece of aluminum that surrounds a plastic container with many ports. These ports are used to pump out chemicals that provide nutrients to the growing vein. Before printing the vein, technicians manually inject several tubes of cultured cells into the print head (similar to a biomass printing cartridge).

4. Vascular Hydrogel Mold

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Technicians place rows of hydrogels in parallel in a petri dish basin, printing granular cell cylinders in the basin. At least one hydrogel cylinder is printed in the middle of the cell to make a small hole in the vein, through which blood will eventually flow in and out.

5. Growing into the vein

Over the next few weeks, the printed veins were placed in another growth medium. Soon, the cells poured out of the hydrogel mold, leaving behind a hollow tube of vascular cells.

6. After special treatment

Next, the printed tubes are placed into a bioreactor, which sprays a specially formulated mixture of proteins, buffers, and other chemicals into the printed veins. This step allows the cells to become functional, reliable veins, maximizing their effectiveness.

7. Printing vein finished product

After a period of time in the bioreactor, the granular cells grow together to form a vein, which can then be implanted into the patient. Because the vein is grown from the patient's own cells, their body is more likely to accept the transplanted vein and not reject it.