It seems that today, the need for human organs is greater than that for humans themselves! There are over 120,000 people on Organ Transplant Waiting Lists worldwide.
With an ever-increasing demand for human tissues and with pharmaceutical drug research requiring more and more tissues to experiment on, this need for human organs and tissues has never been so great.
At the same time, the shortage of human organs for these purposes is also understandable. After all, not many of us would want to go around without a liver, a kidney or perhaps even a heart, would we? Furthermore, organ transplants have raised some moral and ethical concerns.
Perhaps, this shortage will be overcome and these concerns put to rest forever this year as Organovo, a Bio-printing Company which we wrote about back in July, plans to print fully functional human liver tissue through a 3D printer in 2014.
Organovo, the Successor of Evolution?
Evolution may have been responsible for the creation of human organs in the first place but it seems that soon Organovo will take over this job.
Organovo, a San-Diego based bio-printing company, combines tissue engineering with 3D printing.This company uses a unique 3D printing machine, called NovoGen printer to make viable three dimensional tissues.
In contrast, traditional tissue engineering procedures have focused on two dimensional models of tissues and have several limitations, many of which have been overcome by Organovo.
Using their NovoGen printer, Organovo has recently made liver tissue, 500 microns in thickness, capable of surviving in laboratory conditions for as long as 40 days!
This shatters the company’s previous record of 3 days for bio-printed liver tissue. This tissue will be available for researchers by the end of 2014.
3D Bio-printing, From Cells to Tissues to Organs
So, how does Organovo do in days what evolution took billions of years to do? The process starts with viable liver cells and ends with fully functional liver tissue. This method is based upon an invention by Gabor Forgacs and is summarized by Organovo on its website in the following words:
“Organovo’s Bioprinting Process centers around the identification of key architectural and compositional elements of a target tissue, and the creation of a design that can be utilized by a bioprinter to generate that tissue in the laboratory environment.”
This process consists of several steps:
- The component cells of a tissue and the three dimensional architecture in which they are arranged is identified.
- Tissue architecture identified in step 1 is then recreated on a computer to almost exactly the same as that found naturally in the tissue
- Bio Ink is then created, which involves obtaining appropriate cells e.g. for printing human liver tissue, viable human liver cells will be obtained; aggregating the cells to increase their number and depositing them in a hydrogel. This material then serves as “ink” or more appropriately “bio-ink” for the NovoGen Printer to print tissues.
- The NovoGen Printer, which is actually a highly precise 3D printer, then uses this bio-ink and deposits drop after drop and layer after layer of cells in accordance with the computer generated architecture (in step 2). In this way, the cells are arranged in the same three dimensional pattern as they are naturally found in the liver.
- The deposited cells are then allowed to self-assemble into tissues. They divide, form make junctions with neighbouring cells and also form supporting tissue and blood vessels. In this way they assemble to form a living tissue which is very close to the naturally occurring tissue. In the future, this method can be extended to create whole organs.
Organovo’s Liver Vs Traditional Livers
As already mentioned, Organovo has created a three dimensional liver tissue, in contrast to traditional tissue engineering two dimensional models.
In 2D models, which are only a few microns in thickness, the cells lose their natural arrangement and as a consequence, many normal functions as well. This makes them inappropriate for use in experiments.
However, Organovo’s liver tissue, which is more than 500 microns in thickness (the thickness of five paper sheets stacked on top of one another), retains the natural functions of the liver. Furthermore, traditionally engineered tissues survive at most for a few days while Organovo’s liver tissue remains viable for 40 days!
The difference is most apparent in the arrangement of cells. In traditional two dimensional models, the cells have a haphazard arrangement. In Organovo’s Liver tissue Model, however, the cells retain their beautiful natural architecture with normal blood vessels and cell to cell interactions as shown in the following figure:
Prospects of 3D Liver Tissue
While 500 micron thickness of viable liver tissue is far from a whole liver, nevertheless this is a huge achievement. The prospects of bio-printed liver tissue are detailed below:
- Understanding Liver Diseases: Having fully functional liver tissue at their disposal will allow pathologists to do all kinds of experiments and see for themselves, how liver diseases develop and progress. In addition, they’ll be able to discover what factors can protect from or aggravate liver diseases. This was previously not possible, as 2D liver models didn’t provide an adequate representation of liver.
- Development of New Drugs and Treatments: Development of new drugs is becoming increasingly costly. As many as one billion dollars can be spent on research and testing of a single drug. With Organovo’s 3D liver, the testing of drugs for liver diseases will be greatly facilitated. The development of drugs for other diseases will also benefit, since the liver plays a central role in the blood concentration and action of many drugs.
- Liver Transplants: Organovo’s ultimate goal is to print whole livers for transplants in patients of terminal liver diseases like hepatitis. Furthermore, as these livers will be made using patients’ own cells, there will no risk of rejection, which is the single biggest concern in transplant surgeries today. Once this goal is achieved for liver, Organovo will progress to other organs like heart, and kidneys.
A World of 3D Printed Livers
Mr. Joe was diagnosed of terminal hepatitis. It seemed to him that his life was at an end, as he had heard that it normally takes months for transplants to become available and even after the transplant, there are minimal chances of survival.
However, Mr. Joe’s doctor wasn’t concerned at all, since he was well aware of Organovo’s 3D printed liver and immediately took out a few of Mr. Joe’s liver cells. By evening he had a new liver for Mr. Joe and transplanted it at night. The next day, Mr. Joe went home happily, his new 3D printed liver functioning even better than his real liver ever had!
Thanks to advances in Tissue Bio-printing such a day may soon arrive. If Organovo’s vision becomes a reality, all of the 120,000 people on the organ transplant waiting lists will get their organs within hours rather than months.
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