3D printer

Need a new liver, pancreas, or other vital organ?

I'll print one right up for you...that is in about 10 years.

My intern Lakshmi did a great job on her guest piece last week on my lab's blog on the promise of 3D printing in stem cell-based bioengineering including organ and tissue production.

It's an incredibly exciting area of biomedical science.

In theory in the future we could literally have new organs printed by specialized forms of 3D printers (e.g. see the image of a 3D printer at left from Wikipedia) or grown for us to replace old, diseased, or injured organs.

The organs could in principle even be made from our own cells so there would little if any danger of rejection.

The demand for organs for transplant has always far exceeded the supply and it's a tragedy how many folks die waiting for a transplant.

Stem cell-based bioengineering might be a game changer here for hundreds of thousands of patients in coming decades.

But we have a ways to go to make this technology a reality in the clinic. Below are the top 10 hurdles.

  1. Function. Sure, you can print say some muscle off of that cool 3D printer you bought or produce some liver-like product, but does it actually work? Is it truly functional? That's far harder than simply making something that looks like a real tissue. If the organ you printed doesn't function like it is supposed to it is like a fancy looking new car with no engine. Pretty, but useless.
  2. Size matters. Most efforts to bioengineer tissues using 3D printing and other technologies have made tissue end products that are way too small. Scaling up is a huge challenge for a variety of reasons discussed more below.
  3. Contamination. Bioengineering a product to be transplanted into human patients is very different than just making some tissue blog in a lab. Of course we have to start somewhere, but to make a tissue to be used in human patients requires that the product not be contaminated with pathogens, xeno-antigens (e.g. from fetal bovine serum used to grow cells and to keep bioengineered tissues alive), and such. That's much tougher. We need a pure, safe product.
  4. Integration. It's still not enough to churn out a healthy, functional tissue to be used to treat a patient. That lab-produced issue/organ must integrate with the host patient or it will not work right and probably will die. So if you make the tissue outside the patient, you have to find a way to get the host body to meld into the transplanted organ and vice versa. Alternatively, you can try to make the organ de novo in the patient's body, but that poses other challenges.
  5. Vasculature. Organs and tissues are not autonomous. They need nutrients to stay alive and those come from the bloodstream. This point links up with the integration issue in the point above. One of the key things tissues need is a blood supply. This is a huge challenge for bioengineers. Typically when making a tissue or organ in a lab, a bioengineer creates a product that is not vascularized. It's very difficult to get blood vessels into the mix say if you are making a liver in a lab. However, without them the liver will never survive. This also gets back to the size issue. There's a paradox here. Bioengineers need tissues and organs to be made that are big enough to have a meaningful impact on a patient's health, but beyond a certain size, oxygen and other factors cannot diffuse so blood vessels are needed.
  6. Diversity. There is no such thing as an organ or tissue that is entirely composed of only one type of cell. As a result, you cannot just use one type of cell as a lego-like building block to make functional tissues. For example, liver is not just made of hepatocytes. They may be the most common cell in the liver, but there are many others too that perform much need functions. Some organs have dozens of types of cells, while even the need for just a few different cell types present big challenges to engineers.
  7. Immunity. Bioengineers need to find ways to avoid the patient's body rejecting the transplant. Immunosuppressant drugs are an option as with traditional organ transplants, but are less than ideal. Sometimes the body rejects the organ anyone. One exciting option with bioengineered organs is to use the patient's own cells to make them, likely avoiding the immune rejection issue. On the other hand, taking immunosuppressant drugs is an option.
  8. Complex architecture. Most organs and tissues need to be in a certain shape and with a specific organization to work properly. It's not enough to 3D print a homogeneous product. Certain cells need to be in specific places, while other cells need to be somewhere else. Imagine, by analogy, 3D printing a plastic product like a specific part to a machine. All the plastic is the same so it is simple to make. Now imagine you need to print a plastic product that is composed of 10 different kinds of plastic and each kind must be present in only certain places in the product. That is orders of magnitude more difficult and that is the reality of biological products.
  9. Enervation. Ideally, bioengineers would want their lab-produced organs to have nerves as well to fully operate normally and respond to signals in the body. Generating nerves inside of tissues and having them integrate with the host is even more difficult than blood vessels. The expression "that takes some nerve!" takes on a whole new meaning here.
  10. Cost. To make functional organs via 3D printing and other bioengineering approaches will be very labor intensive and expensive. The first true engineered organs may cost millions of dollars each. At the same time serious organ disease and organ failure cost billions if not trillions of dollars in healthcare costs and untold suffering....so even if lab-grown organs are expensive, they may be relatively less expensive than one might imagine. And once they are made, over the subsequent years the costs will come down dramatically.

I'm confident that tissue engineers can overcome these problems in the coming decades. I'm not sure that all organs can be grown from stem cells in a lab, but I believe that in a few decades that there will be some organs available that truly work to help patients either by replacing faulty organs or supplementing their functions.

This piece was originally posted at ipscell.com by me.