Bone marrow stem cells

Article about the three different types of stem cells found in bone marrow tissue. These are mesenchymal, endothelial and hematopoietic stem cells.

The bone marrow is a rich source of many different types of stem cells. But first let’s begin with what the bone marrow actually is. Wikipedia defines the bone marrow as “the flexible tissue found in the interior of bones” whereas the medical-dictionary defines it as “the soft, fatty, vascular tissue that fills the bone cavities, having a stroma of reticular fibers and cells.”

The bone marrow contains three different types of stem cells:

Mesenchmal stem cells
Hematopoietic stem cells
Endothelial stem cells

Femoral head with the bone marrow exp...

What are mesenchymal stem cells ?

Mesenchymal stem cells are multipotent stem cells (you can read more about potency here), with the ability to transform into the cells that comprise the skeletal tissue. The main skeletal cells are chondrocytes, adipocytes and osteoblasts. The chondrocytes are the cells that form the cartilage tissue, which is the protective layer that covers the bones in our joints. Adipocytes (also known as lipocytes and fat cells), are the cells that compose adiposal tissue, commonly known as fat. Finally, osteoblasts are the the cells that form our bones.

Mesenchymal stem cell applications
As of today there is no FDA-approved treatment involving the use of mesenchymal stem cells. However, many researchers are experimenting on them and due to their ability to transform into skeletal cells, it is believed that they may one day help with the treatment of many conditions involving the loss of skeletal cells, including:

Osteoporosis
Osteoarthritis
Heart failure

There is even a human clinical trial currently running for the treatment of Cerebral Palsy. The company running the trial is called Astrostem

Colony of mesenchymal stem cells

What are endothelial stem cells

Endothelial stem cells are oligopotent stem cells with the capacity to differentiate into the cells that form the endothelium. The endothelium is the thin layer of cells that lines the interior surface of blood vessels and lymphatic vessels. There are two types of endothelial cells. The ones that are in direct contact with blood are called vascular endothelial cells, whereas those that are in direct contact with the lymph are called lymphatic endothelial cells.

Image showing the location of endothelial cells

What are hematopoietic stem cells ?

Hematopoietic stem cells are multipotent stem cells with the capacity to develop into all the cells of the blood and lymphatic system. These cells are the following:

Basophils
Dendritic cells
Eosinophils
Erythrocytes
Macrophages
Megakaryocytes
Monocytes
Neutrophils
Platelets
B-cells
NK-cells
T-cells

T-cell (right), a platelet (center) and a red blood cell (left)

Hematopoietic stem cells applications
For now the only FDA-approved treatment involving hematopoietic stem cells is a therapy called “hematopoietic stem cell transplantation”. Essentially, it is the transplantation of hematopoietic stem cells in a patient that had his own hematopoietic stem cells previously destroyed. The operation has been around for more than 30 years and is usually carried out in cancer victims. Some types of cancers that this treatment is used are the following:

Acute lymphoblastic leukemia
Acute myeloblastic leukemia
Chronic myelogenous leukemia
Hodgkin's disease

A lot of research is currently going on hematopoietic stem cells and it is believed that the may one day be used in the treatment of the following conditions: