In this blog post, we will look at the principles of how stem cells and tissue engineering combine to regenerate damaged cartilage and how the actual treatment process is carried out.
These days, you can see advertisements for cartilage stem cell therapy on the streets. Some people may have wondered if stem cell research is a field that is no longer in vogue, and they may have been puzzled as to how cartilage can be treated using stem cells. However, stem cells are still being actively researched by many scientists, and they are attracting particular attention in the field of regenerating artificial organs such as skin and cartilage. Long-term regeneration, which was once considered a technology of the distant future, is now gradually becoming a reality through stem cells. In some areas, it has already advanced to the point where it can be applied to actual clinical treatment beyond the research stage. Let’s take a closer look at cartilage regeneration, one of the stem cell treatments that is currently being applied in practice.
First, let’s take a look at how stem cells are used in artificial organ regeneration. Stem cells are a key element of tissue engineering, a discipline that aims to artificially create living tissue in an in vitro environment. Tissue engineering deals with everything related to the body, including bones, skin, and internal organs, and can be divided into three main elements: scaffold, stem cell, and growth factor. Tissue engineering is a cutting-edge discipline that creates human organs, so it may seem complex and daunting, but in reality, the key is to ensure that these three elements are properly fulfilled. So, how do these elements combine to form human organs?
Tissues are formed by the aggregation of numerous cells with specific functions. This is why the cells that exist in tissues that perform different functions, such as bones, skin, and cartilage, have different shapes and functions. What is interesting is that these cells, which have different shapes and different roles, actually share the same origin. In other words, the root of these cells is stem cells. Since stem cells have the potential to differentiate into various cells, tissue engineering uses them to differentiate into the desired cells to create specific tissues. The key issue here is how to differentiate stem cells into the desired cells. To make this easier to understand, let’s imagine that a stem cell is a baby and we are raising this baby to be a child who loves books.
The first thing we need to raise a baby is a space to grow. Cells also need a space to grow naturally, and the human body is the original environment for this. However, since stem cells must be cultured in an artificial in vitro environment, a similar space must be created for these cells to feel as if they are in their original environment. This space is called a scaffold. Importantly, the environment in which cells grow varies from tissue to tissue. For example, cartilage cells grow in a hard environment attached to bone, while skin cells grow in relatively soft muscle tissue. Therefore, when raising a baby, you should create an environment that is suitable for the growth of specific cells, just as you would decorate a room with many books.
So, if you provide a special room, will the baby grow up to be a child who loves books? No, it won’t. There is one more thing that is needed here. It is external stimuli, or inducers. Just as a parent guides a baby to read a book, cells also need growth factors to provide direction. Growth factors are actually hormones that guide the direction of stem cells when they differentiate into specific cells in the human body. When growth factors are injected together in an in vitro environment, stem cells recognize them and differentiate into specific cells.
Now, let’s get back to cartilage regeneration therapy. Cartilage is a flexible tissue that reduces friction and acts as a buffer between bones. Cartilage is composed of chondrocytes and the matrix they produce, which is a flexible gel containing water, collagen, and hyaluronic acid. Cartilage wears out gradually with repeated use, and many people suffer from knee cartilage pain as they age. Why does cartilage only wear out while skin and bone regenerate when damaged? This is because cartilage has no blood vessels. When skin or bone is damaged, stem cells in the bone marrow migrate through blood vessels to form new tissue at the damaged site. However, cartilage without blood vessels cannot undergo this regeneration process, and cartilage ages as we get older. To solve this problem, scientists have developed a method for cartilage regeneration using stem cells.
First, stem cells are collected from the bone marrow. Stem cells grown from bone marrow have the ability to differentiate into bone, skin, and cartilage. The stem cells are cultured on a support suitable for the growth of chondrocytes, and growth factors are injected to induce the stem cells to differentiate into chondrocytes. These chondrocytes secrete substances such as collagen and hyaluronic acid to form a matrix, and when the formed chondrocytes and matrix are transplanted into the body, cartilage can be regenerated as if it were the original tissue.
We have now learned about the process of tissue regeneration using stem cells. This field is actively being researched because it can be regenerated without an immune response using the body’s own stem cells, and it is expected that regeneration of more complex organs beyond cartilage will soon be possible.
