The combination of stem cells and tissue engineering has made cartilage regeneration possible. Stem cells are induced with specific environments and growth factors to differentiate into chondrocytes, which are then transplanted to restore cartilage.
These days, it’s not uncommon to see ads for cartilage stem cell therapy on the street. While some people may wonder if stem cell research is a dying field and wonder how stem cells can be used to treat cartilage, stem cells are still being actively researched by many scientists, especially in the field of artificial organ regeneration, including skin and cartilage. Organ regeneration, once thought to be a technology of the distant future, is now gradually becoming a reality with stem cells. In some areas, it has already advanced beyond the research stage to the point where it is being applied in clinical practice. Let’s take a closer look at cartilage regeneration, one of the stem cell treatments currently in practice.
First, let’s take a look at how stem cells are used in artificial organ regeneration. Stem cells are a key component of tissue engineering, which aims to artificially create living tissue in an in vitro environment. Tissue engineering covers everything related to the body, including bones, skin, and internal organs, and can be divided into three main components: Scaffolds, stem cells, and growth factors. Tissue engineering is a cutting-edge discipline that creates human organs, so it sounds complicated and grandiose, but in reality, it’s all about getting these three elements right. So how do they come together to form a human organ?
Tissue is formed by the aggregation of many cells with specific functions. Because of this, the cells in different tissues that perform different functions, such as bone, skin, and cartilage, have different shapes and functions. What’s interesting is that these differently shaped, differently functioning cells actually share the same origin: stem cells. Stem cells have the potential to differentiate into a variety of cells, so in tissue engineering, we can differentiate them into the desired cells to create a specific tissue. To understand this better, let’s imagine a stem cell as a baby and imagine that you want to grow it into a child who loves books.
The first thing a baby needs to grow is space to grow. Cells also need a place to grow naturally, and naturally, the inside of the human body is that environment. But since we need to grow stem cells in an artificial in vitro environment, we need to create a similar space for them to feel like it’s their natural environment. This space is called a scaffold. Importantly, the environment in which cells grow is different for each tissue. For example, cartilage cells grow in a stiff environment attached to bone, while skin cells grow in relatively soft muscle tissue. So, just as you might decorate a baby’s room with lots of books, you need to create the right environment for specific cells to grow in.
So, if you just provide a special room, will your baby grow up to be a book-loving child? No. There’s one more thing they need. It’s an external stimulus, or inducer. Just like parents encourage their babies to read, cells need growth factors to give them direction. Growth factors are actually hormones that guide stem cells in the body as they differentiate into specific cells. In an in vitro environment, when growth factors are injected together, the stem cells recognize them and differentiate into specific cells.
Now let’s go back to cartilage regeneration therapy. Cartilage is the elastic, friction-reducing, cushioning tissue between bones. Cartilage is made up of chondrocytes and the matrix they produce, which contains water, collagen, hyaluronic acid, and other substances to form an elastic gel. Cartilage gradually wears down with repeated use, and many people suffer from knee cartilage pain as they age. While skin and bone regenerate when damaged, cartilage just wears out. This is because cartilage has no blood vessels. When skin or bone is damaged, stem cells from the bone marrow migrate through the blood vessels to form new tissue at the site of the damage. But without blood vessels, this regenerative process is impossible in cartilage, which is why cartilage ages with age. To solve this problem, scientists have developed a way to regenerate cartilage using stem cells.
First, stem cells are harvested from bone marrow. Stem cells grown in bone marrow have the ability to differentiate into bone, skin, and cartilage. These stem cells are then cultured on a support suitable for chondrocytes to grow, 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 chondrocytes and matrix are then transplanted into the body, they can regenerate cartilage as if it were their own tissue.
So far, we’ve learned about the process of tissue regeneration using stem cells. This is an active area of research because it utilizes the body’s own stem cells to regenerate without an immune response, and it is expected that it will soon be possible to regenerate more complex organs beyond cartilage.
