In this blog post, we’ll explore the principles behind using stem cells and tissue engineering to regenerate damaged cartilage, as well as how the actual treatment process works.
These days, you often see advertisements for cartilage stem cell treatments on the streets. Some people may wonder if stem cell research is a field past its prime and may be puzzled as to how stem cells can be used to treat cartilage. However, stem cells are still being actively researched by countless scientists and are garnering particular attention in the field of artificial organ regeneration, such as for skin and cartilage. Organ regeneration, once considered a technology of the distant future, is now gradually becoming a reality through stem cells. In some fields, the technology has already progressed beyond the research stage and is now ready for application in actual clinical treatments. So, let’s take a closer look at cartilage regeneration, one of the stem cell therapies currently being applied in practice.
First, let’s explore how stem cells are utilized in artificial organ regeneration. Stem cells are a core element of tissue engineering, a field that aims to artificially generate biological tissues in an in vitro environment. Tissue engineering covers everything related to the human body, including bones, skin, and internal organs, and can be broadly divided into three key elements: scaffolds, stem cells, and growth factors. While tissue engineering may seem complex and formidable as a cutting-edge field focused on creating human organs, the core of the process actually lies in ensuring 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. For this reason, the cells found in tissues that perform different functions—such as bone, skin, and cartilage—differ in both form and function. What is interesting is that these cells, which differ in shape and role, actually share the same origin. In other words, the root of these cells is the stem cell. Since stem cells have the potential to differentiate into various cell types, tissue engineering involves inducing them to differentiate into specific cells to create particular tissues. The key challenge here is how to induce stem cells to differentiate into the desired cell types. To make this easier to understand, let’s use an analogy: imagine a stem cell as a baby and raising that baby to become a child who loves books.
The first thing needed to raise a baby is space to grow. Cells also need a space where they can grow naturally; originally, the inside of the human body provides that environment. However, since stem cells must be cultured in an artificial, in vitro environment, we must create a similar space where these cells can feel as if they are in their natural environment. This space is called a scaffold. The key point is that the environment in which cells grow differs 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, just as we set up a room full of books when raising a baby, we must create an environment suitable for the growth of specific cells.
So, if we simply provide a special room, will the baby grow up to love books? No, that is not the case. There is one more thing needed here: external stimuli, or signaling molecules. Just as parents encourage a baby to read books, cells need growth factors to guide their direction. Growth factors are actually hormones that guide stem cells in the human body to differentiate into specific cell types. When growth factors are introduced into an in vitro environment, stem cells recognize them and differentiate into specific cell types.
Now, let’s return to the topic of cartilage regeneration therapy. Cartilage is a tissue that acts as a cushion between bones, reducing friction and providing elasticity. Cartilage consists of chondrocytes and the matrix they produce; this matrix contains substances such as water, collagen, and hyaluronic acid, giving it an elastic gel-like form.
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 only wears away—but why is that? It is because cartilage lacks blood vessels. When problems arise in the skin or bone, stem cells from the bone marrow travel through blood vessels to form new tissue at the damaged site. However, since cartilage lacks blood vessels, this regenerative process is impossible, leading to cartilage aging as we get older. To address this, scientists have developed methods for cartilage regeneration using stem cells.
First, stem cells are harvested from the bone marrow. Stem cells derived from bone marrow have the ability to differentiate into bone, skin, and cartilage. The harvested stem cells are cultured on a scaffold suitable for cartilage cell growth, and growth factors are added to induce the stem cells to differentiate into cartilage cells. These cartilage cells secrete substances such as collagen and hyaluronic acid to form a matrix. When the resulting cartilage cells and matrix are transplanted into the body, they can regenerate cartilage just like the body’s own tissue.
We have now explored the process of tissue regeneration using stem cells. This field is actively being researched because it allows for regeneration without an immune response by utilizing the body’s own stem cells, and it is expected that, in the near future, the regeneration of organs more complex than cartilage will also become possible.
