How to implement tissue engineering
Tissue engineering is the idea that it is possible to create high-performance artificial organs and tissue by combining the 3 elements of "living cells", "matrix", and "physiologically active substances". Well then, what kinds of issues need to be resolved in order to actually realize tissue engineering? This time, we would like to consider this question.
As one might expect, it is the cells that play the leading role in tissue engineering to increase cells. Technology for greatly and successfully increasing our bodies' cells must be created. For that, we first need a method for greatly increasing cells. Our bodies are made up of 60 trillion cells to begin with. Even if we only want to make a very small amount of tissue, we will need at least several hundred million cells. Tissue engineering cannot be realized unless it is possible to greatly increase cells outside of the body. The most ordinary of the existing methods of culturing cells is to inoculate a plastic culture plate with the cells and fill it with liquid culture medium. This will work to increase the cells. If you look at the medium under a microscope, it will appear as though amoeba-like single-cell organisms have rapidly proliferated. The environment may be different from inside the body, but there is no doubt about it: the cells have increased.
But there is a reason why I said we need technology for "successfully increasing" the body's cells. Even if we are able to increase cells greatly, it will mean nothing if the cells will not work as they did when they were inside the body. If they don't, they are just cells that were forced to increase unnaturally on plastic. As we saw in the 3rd chapter, not all cells retain the ability to differentiate. In many cases, the cells will lose this function at the stage where they are greatly multiplied. We call this "dedifferentiation", and the fact is that some cells do not turn out as we wish.
Technology for greatly increasing cells and the ability to maintain differentiability depend entirely on the method of culturing the cells. It is not the case that this kind of ideal cell culturing can be achieved for all types of cells with the technology that we currently possess. Improvements in culture media, the development of different types of culture plates, and the creation of ideal culturing technology will be very important.
Of course, technology for developing matrices is also important. Matrices that have a harmful effect on the body cannot be used. It is also best if artificial matrix of the kind made in a factory will disappear soon after it is transplanted and be replaced by natural matrix produced by the surrounding cells. At the present point in time, this requirement cannot be completely satisfied, but many research studies are being conducted in the hopes of creating matrices that are ideal for each type of tissue.
It would seem as if we could create splendid artificial organs and tissue if we could combine ideally cultured cells with ideally produced matrices, but in truth, one final hurdle remains. That is the requirement that the cells arrange themselves in an orderly fashion. The cells in our bodies line up in a very regular manner. Judging from the appearance of skin, bones, or cartilage, one might think that the cells are arranged quite randomly, but organs like the liver and kidneys consist of a wide variety of cells that are arranged very neatly in a preplanned order. An organ is an orderly array of hundreds of millions of cells or more.
Unfortunately, we do not presently have technology for getting cells to line up in an orderly manner. We can only rely upon their inherent autonomy to align them appropriately once they are in the body. We now know that skin or bone can be transplanted in a piecemeal manner without many problems. However, this is not the case with more complex organs. Steady sober research on these more mundane topics is indispensable to the development of tissue engineering.