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Ex-vivo Organ Perfusion: Why don't organs live in vitro for long?



Hello again!


Sano, an engineer who develops perfusion devices every day, may someday seriously think to himself "I wonder if I can invent a device that can culture organs in bottles, like those that have appeared in science fiction movies for a very long time."


"Why can't organs live when they're outside of the body?" he might ask.


Have you ever thought of that?


Well, ladies and gentlemen, I believe that "making the best use of" and the "making" of organs, in vitro, is one of the ultimate goals of organ research, including regenerative medicine. In order to successfully achieve such goals, it is essential that long-term perfusion must be utilized in vitro, over a long period of time, and bioreactors that can make use of the organs are also required.


The previous article explains this in greater detail, so please feel free to refer to it.


Article: What is a bioreactor? Manufacturers explain everything from cell culture to regenerative medicine


One issue that requires further investigation is how perfusion liquid can be made to spread to the entire organ, even though it will eventually hit the problem when perfusing for a long period of time. In this article, I'll discuss this issue in depth.




Table of contents

  1. Gravity also applies to organs.

  2. Outside the body, it is difficult to spread organs "evenly"

  3. When the blood circulation is poor...

  4. The research

  5. Original purpose

  6. Summary



Gravity also applies to organs.


Even in humans, people who are bedridden for a long period of time develop pressure ulcers and bedsores.


The same is true for organs when they are taken out of the body.


If you are reading this article and have removed organs yourself, you’ll obviously have an image in mind when asked what the state of a removed organ looks like. If not, then imagine a piece of meat that has not been cut by a butcher’s knife at the local butchers, and you can start to imagine it, at least... The organs are basically soft and if you put them on an even surface, they will spread. The weight of the entire organ is applied to the bottom of the surface.


At this stage, it is difficult for blood to reach the bottom part of the organ (where weight is applied), and because of that it reaches the so-called ischemia state.




Outside the body, it is difficult to spread organs "evenly"



In short, it is surprisingly very difficult to evenly circulate blood to the entire organ that has been removed from the body.


In actuality, in vitro organ culture the part where blood does not reach is necrotic, capillaries are torn, and this appears in the form of ‘leakage’.


No matter how much perfusion liquid is flowing from the artery, it leaks and does not return from the vein.




When the blood circulation is poor...



What do you do when your blood circulation is poor or when stiffness occurs in your muscles (stiff shoulders, etc.)?

A good massage usually does the trick…

But what happens if you massage an organ that has been taken out of the body: will the blood circulation within it also improve?


I decided to do some research to find out.




The research



The study perfused the small intestine of rats and the femoral skeletal muscles of rats, comparing them in two separate groups: those that had nothing done to them and those that got massaged.

The massage was performed by pressurization, as well as by putting the organs in a sealed space which had gas injected into it, intermittently. We created a system that can be pressurized while perfusion occurs.

And the perfusion state obviously improved in the group where both the small intestine and the muscle were intermittently pressurized.


In the small intestine, diluted blood was shed, but if nothing additional was done to it, the blood would retreat to the bottom of the small intestine due to gravity. The upper part hardly circulated any blood, but when intermittent pressurization was performed, the blood was firmly circulating at the top.


In the muscles, if nothing was done to them, the return of blood from the vein decreases from around the start of perfusion (around 2-3 days), with leakage occurring from the outside of the vein. But when pressurized intermittently, they successfully obtained a return from the vein for 14 days.


In addition, we measured tissue activity (ATP) and looked at the tissue images in sections, but it became apparent that intermittently pressurized muscles were better.



Original purpose



In fact, in order to solve the problem of leakage, that initially occurred when perfusioning organs in vitro, should we apply pressure like in vivo? At first, I applied a certain pressure, but nothing changed . So why not pressurize intermittently(?), I thought, and went on to do the research, together with developing the equipment needed to do so.


Summary

To summarize the results, I found that:


In long-term perfusion, the question of how to stop a leak needs to be addressed, as well as how to spread perfusion liquid evenly throughout the process


Pressurizing intermittently improves the condition of perfusion.


As a result, perfusion conditions improved in the small intestine and skeletal muscle.


I can therefore conclude that if want to perform long-term perfusion, we will need to find solutions to the problems of how to spread perfusion liquid to the whole organ, as well as how to stop leakage.


Thank you for reading to the end.


Do you have any ideas about whether you would attempt to do this kind of perfusion after reading the contents of this article?


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