Mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into bone, muscle, tendon, cartilage, and fat cells. They are primarily found in the bone marrow, and their main function is the production and repair of skeletal tissues. MSCs have great potential in the field of regenerative medicine, and could one day be used as treatments for bone and cartilage injuries, ischemic heart disease, and inflammatory conditions.
What is a Mesenchymal Stem Cell?
Mesenchymal stem cells (MSCs) are adult stem cells found in the bone marrow, fat tissue, and umbilical cord. They are multipotent and can differentiate into a variety of different cell types including bone, muscle, tendon, cartilage, and fat cells.
Location of Mesenchymal Stem Cells
Mesenchymal stem cells are traditionally located in the bone marrow. However, they are also found in fat tissue, blood, and umbilical cords.
Function of Mesenchymal Stem Cells
Mesenchymal stem cells give rise to a variety of cell types, including muscle, bone, tendon, cartilage, and fat cells. Therefore, they play a central role in the growth and repair of skeletal tissues.
In the event of tissue damage, MSCs migrate through blood vessel walls to reach the site of the injury. Once there, they can differentiate into specialized cells that are used to repair and regenerate damaged tissues. They also secrete cytokines chemokines and growth factors that help with tissue repair.
Differentiation of Mesenchymal Stem Cells
Mesenchymal stem cells are multipotent stem cells and can differentiate into chondrocytes, osteoblasts, adipocytes, myocytes, and tenocytes.
Chondrogenesis is the formation of cartilage tissue, which is important for the repair of skeletal tissues.
MSCs differentiate into chondrocytes, which are the specialized cells responsible for cartilage formation. Chondrocytes secrete molecules (such as collagen) that form the cartilage extracellular matrix, which connects and supports the tissues of the musculoskeletal system.
Mesenchymal stem cells play a central role in bone fracture repair by differentiating into osteoblasts. Osteoblasts are specialized cells responsible for the formation of new bone tissue and secrete molecules that contribute to the bone matrix.
MSCs can also differentiate to form adipocytes (AKA fat cells). Adipocytes are the primary component of adipose tissue, so they are vital for the formation of new fat tissue.
Myoblasts play a central role in myogenesis, or muscle formation. When a muscle is damaged, MCSs migrate to the site of the injury where they differentiate to form myoblasts. The myoblasts may fuse to damaged myofibers in the muscles, or fuse together to form myotubes. The myotubes will eventually mature and form new muscle fibers.
Tenogenesis is the formation of tendon tissue and is initiated when MSCs differentiate to form tenocytes. Tenocytes are specialized cells that secret collagen molecules, which aggregate to form collagen fibrils. A group of collagen fibrils forms a collagen bundle, a group of collagen bundles forms a fascicle, and a group of fascicles forms a tendon.
Mesenchymal Stem Cells and Inflammation
MSCs also function as immunosuppressive cells with strong anti-inflammatory functions. By releasing cytokines and chemokines, MSCs can suppress almost all the cells of innate and adaptive immune systems. This helps to maintain immune homeostasis and promotes immune tolerance, which helps to prevent unnecessary or excessive activation of the immune system.
Clinical Uses for Mesenchymal Stem Cells
The ability of MCSs to self-renew and differentiate into different types of cells means they have enormous potential in the field of regenerative medicine. MSC therapies are not currently available, but research into their possible applications is ongoing, and they could eventually be used in bone and cartilage repair, heart and blood vessel repair, and as a treatment for a variety of other diseases.
Bone and Cartilage Repair
MSCs can differentiate to form osteoblasts and chondrocytes, both of which are vital for bone and cartilage healing. Therefore, MSCs could be used to treat otherwise hard-to-fix bone and cartilage injuries.
Another potential application of MSCs is cartilage regeneration, which could improve the symptoms of osteoarthritis. Osteoarthritis is a chronic condition in which the cartilage that usually cushions the ends of the bones is worn away. Studies have shown that injecting MSCs into the affected joints of osteoarthritis sufferers leads to increased cartilage thickness and, therefore, a reduction of pain and other symptoms.
Heart and Blood Vessel Repair
Recent studies involving MSCs suggest that these stem cells may also contribute to the formation of new blood vessels (a process known as neovascularization). If MSCs can be used to reconstruct blood vessels in the heart, they could eventually be used to treat ischemic heart disease.
Treatment for Inflammatory Diseases
As immunosuppressive cells, MSCs may also be useful for the treatment of inflammatory diseases such as graft versus host disease (GVHD), sepsis, and irritable bowel syndrome (IBS). However, research in this field is ongoing.
Mesenchymal Stem Cells vs. Haematopoietic Stem Cells
Mesenchymal and hematopoietic stem cells are both found in the bone marrow, but they differentiate into different cell types. Hematopoietic Stem Cells are blood stem cells and give rise to different types of blood cells (including red blood cells, white blood cells, and platelets).