Custom human organs: do I need to print a new heart?

All cells in our body have the same DNA, inherited from our parents. And yet they are not all the same. Why are heart cells different from lung cells? How do they know the role they have to play?

Science was born out of unresolved questions and these were some of those raised by the scientists who started the first tissue engineering labs. And soon they found the answers.

The origin of each of us results from two cells, coming from our father and our mother. These cells, by uniting and dividing, give rise to stem cells which, in turn, can generate a complete human being. This human being is made up of different cells, with different functions, grouped into tissues, which in turn form the organs.

What happens in embryonic development so that different organs are formed from genetically identical cells? Well, as cells divide and differentiate, signals are produced that cause not all cells to express all genes. So the cells of the heart, despite having the same DNA as those of the lungs, express certain genes that tell them to contract and beat, and those that cause the lung cells to take in oxygen are silenced.

mend broken hearts

With all of this information on the table, in 2006 Professor Shinya Yamanaka, Nobel Prize in Medicine, considered the following: If a stem cell, receiving external signals, is able to differentiate into an adult cell, the process can be reversed? Take an adult cell, add signals to it and turn it into a stem cell? He tried it and the answer was yes: there are “master” stem cells from which cells of any tissue can be obtained.

On the other hand, our body is constantly taking damage and needs to repair itself. There are organs capable of doing this, such as skin and bones. Instead, there are others with functions so advanced and complex that their specialized cells have lost the ability to divide and regenerate after damage. A representative example would be the heart.

Currently, heart disease is the leading cause of death worldwide. We all know someone who has had a heart attack. What happens in a heart attack is that the cells in an area of ​​the heart die, they cannot perform their function, and the heart is not able to recover that damaged area.

The current treatment? The transplant. But even in Spain, which is a world leader in the field of organ transplants, there are not enough hearts to cover the demand. In addition, the patient receives medication for life to prevent the transplanted heart from being rejected by the immune system.

The good news is that, thanks to Professor Yamanaka’s discovery, we can obtain heart cells in the laboratory. Moreover, if the starting cells are obtained from the patient who suffers from the heart disease (from his skin, for example), the problem of rejection is avoided.

Cells are not enough: we need scaffolding

At the end of the 20th century, strategies began to be proposed consisting in filling the areas of the heart that had lost them following a heart attack with heart cells. But the heart is too complex an organ and cannot be rebuilt with cells alone: ​​the structure and the scaffolding where they are located are just as important.

This scaffold is called the “extracellular matrix” and apart from providing structure it also has other fundamental functions such as providing the necessary mechanical properties of stiffness, elasticity and toughness. This is what makes bones hard and can perform the function of a bone, the heart is more elastic and allows cells to beat, etc.

In the case of the heart, not only the characteristics of this matrix are important, but also its organization in space, which increases its complexity.

Over the past twenty years, materials capable of mimicking the extracellular matrix, called “biomaterials”, have been developed. 3D printing technology is also being developed. If with a 3D printer we can make almost any object in our homes, why not try it with an organ?

3D bioprinters, in addition to the manufacture of organs for transplants, represent a great advance for personalized medicine. If a heart is made with a patient’s own cells, treatments or combinations of drugs could be tested on the organ before administering them to the patient. It sounds like science fiction, but it’s already hitting the labs.

(c) Conversation / María Pérez Araluce (University of Navarre) / image: 123rf


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