Tales of Regenerative Medicine

What is Tissue Engineering?

In 1993, a physician and an engineer in the United States proposed the new concept of "Tissue Engineering". They explained it as "drawing upon a skillful blend of life sciences and engineering to create substitutes for organs and tissue that have lost their functions". "Tissue engineering" meant a way of using engineering or industrial technology to create material that could substitute for the tissues of the human body. (In Japan, Japanese kanji characters are sometimes used to represent tissue engineering instead of a Japanized pronunciation of the English words.) Let's look at tissue engineering in a little more detail.

Artificial organs are man-made organs such as an artificial heart or artificial kidney. Although not as complex as artificial organs, artificial tissue like artificial skin and bone has also come into use in treatment. Although their applications are limited, such artificial organs have gradually come into practical use thanks to the efforts of many people. What, then, is tissue engineering? How does it differ from artificial organs? The author of the quote cited at the beginning of this chapter was U.S. physician Joseph Vacanti, who was a pediatric gastrointestinal surgeon. The engineer that was the coauthor of the concept was Robert Langer, a researcher whose specialty was materials technology. The exciting thing about the concept of tissue engineering that they conceived was that it proposed using living cells to create artificial organs and tissue.

In previous chapters, we talked about how our bodies are made up of 60 trillion cells. We also discussed that some of these cells were called stem cells which possessed the ability to increase themselves. We also stated that the cells in our bodies are actually embedded in a structure made from a substance called matrix.
The two scientists introduced above thought that it should be possible to artificially increase a patient's cells and then create body tissue and organs by skillfully combining those cells with matrix produced in a factory. Skin, mucous membranes, bones, and cartilage all have cells that are characteristic of each. Moreover, they have matrices made of suitable material. Of course, in our bodies, the cells themselves create the matrix, but the scientists thought it should be possible to restore lost tissue and organs by preparing artificial matrix and combining it skillfully with living cells. This is the basic idea behind tissue engineering.

To be sure, technologies for greatly increasing the number of cells from our bodies have been developed with advances in biology and other sciences. Moreover, our knowledge about the matrix materials that give structure to the body has rapidly increased as we have learned more about body mechanisms and fine structure. That being the case, we should be able to increase the living component of the body (the cells) by means of technologies that multiply cells, and then use engineering technology to create the matrix part. By skillfully combining these, we would then create artificial organs and artificial tissue with functions and structure never seen before.
The concept of tissue engineering proposed by the two scientists called for adding to this combination of cells and matrix something with the effect of exerting effective action on the body (This is called a physiologically active substance), to artificially create organs and tissues from these 3 elements: "cells", "matrix", and "physiologically active substance". Compared to artificial organs and tissue that were simply manufactured as industrial products, this would contain living cells and could be expected to have various functions. It could be expected to have something of the various effects created by cells. The cells themselves would adhere to it, and perhaps it would function smoothly as if it had been there all along.