The Two Types of Bone Marrow

Bone Marrow Transplantation and Stem Cell Therapies are literally “the heart” of many clinical trials and research efforts. (1) Many people are struggling to survive and cope as they live with chronic diseases, blood disorders, and cancer. As a result, the science community is actively working with biorepositories to acquire quality bone marrow and stem cell samples needed for clinical research. (2)

What Exactly is Bone Marrow? 

Bone marrow is the soft, malleable tissue located in the center of the bone. It is comprised of connective tissues, blood vessels, and capillaries that are responsible for the production of different cell types that create and sustain life. Bone marrow is responsible for generating billions of new blood cells every day. There are two distinct types of bone marrow – yellow marrow and red morrow. On average, most adults have about 2.5kg of bone marrow, half of which consists of the red morrow type. 

Red Bone Marrow (Myeloid Tissue)

Red Bone Marrow is responsible for producing three primary cell types:

• Red Blood Cells (RBCs) - Red blood cells are responsible for carrying oxygen throughout the body. It also carries carbon dioxide away from the tissue and back to the lungs to exhale. Red blood cells have a life span of about 120 days.

• Platelets – Platelets are responsible for preventing excessive bleeding and assist the blood clotting process after injury. Platelets have a life span of about ten days.

• White Blood Cells (WBCs) - White blood cells assist the body in fighting infection. White blood cells have a life span of only a few hours to a few days.

When we are born, our bodies contain all red bone marrow. Later, as we age, it becomes yellow bone marrow. It is found mainly in the medullary cavities (within the flattest bones) of the body: hip bone, breast, skull, vertebrae, ribs, shoulder blades, and in the cancellous material at the ends of the long femur bones and humerus. (3) 

Yellow Bone Marrow

Yellow Bone Marrow is called yellow because of its high concentration of fat cells. It is responsible for aiding in the storage of fats in cells called adipocytes. Yellow bone marrow is responsible for producing cartilage, fat, and bone. In cases of severe blood loss, the yellow bone marrow has the potential to turn back from yellow to red bone marrow. 

Bone Marrow Contains Two Types of Stem Cells

Bone marrow produces two specific types of stem cells, hemopoietic stem cells, and stromal stem cells. These are human cells with the ability to differentiate into other types of cells, making them the building blocks of functional life. Researchers discovered that stem cell-derived therapies are capable of correcting advanced disease, blood disorders, re-growing limbs, and regenerating failing organs. 

Hemopoietic Stem Cells (HSCs)

HSCs are the foundation cells for the production of red blood cells, AND it is capable of renewing itself. HSCs are essentially a multipurpose type cell, they can differentiate themselves, but it also has the power to mobilize away from the bone marrow into the main bloodstream and undergo apoptosis (self-destruction). 

 Mesenchymal (MSCs) or Stromal Stem Cells 

These are cells harvested from adult bone marrow, adipose tissues, neonatal tissues. They make up the connective tissues (the supportive tissues surrounding vital organs). The most common stromal cell types are fibroblasts and pericytes. The highlight of these types of stem cells is their ability to proliferate and their immunosuppression functionality. (4) 

Bone Marrow Diseases and Transplantation

Genetics and other factors can hinder the ability of the bone marrow to function properly. Abnormal functionality of the bone marrow’s ability to create stem cells results in bone marrow disease or disorders that require the need for transplantation and/or advanced treatment. (4) 

Bone marrow diseases are challenging to treat and are, in most cases, assigned a poor prognosis. This is where the bone marrow transplants come into practice. (4) However, one of the biggest challenges is to a bone marrow donor capable of matching the patient in need. (5) 

Did You Know? 

Only 30% of patients requiring a bone marrow transplant have a matching bone marrow donor within their family unit.

The two most important factors in matching a donor to a patient are 1) age and 2) ancestry. 

Bone Marrow Diseases:

• Leukemia - a cancer of the blood where the bone marrow makes abnormal white blood cells

• Aplastic Anemia – A condition in which the bone marrow does make a sufficient amount of red blood cells.

• Myeloproliferative Neoplasms (MPN) - This is a cancerous condition that comes about when the body makes too many red or white blood cells and platelets

• Lymphoma cancer– While not directly affecting the bone marrow, it involves the immune fighting cells o the immune system that resides in the bone marrow, spleen, and other parts of the body.

 Bone Marrow and Stem Cell Research 

Bone marrow and their stem cell producing abilities take center stage when it comes to new drug discoveries and their potential to regenerate and heal the body. Researchers use both types of bone marrow extensively for research purposes to help understand better their diverse mechanisms of actions. The future of bone marrow transplants and solving the mysteries of advanced diseases hinge upon finding ways of harnessing the cell differentiating power of stem cells. (7) 

Using a Biorepository for Long Term Storage for Bone Marrow and Stem Cell Products

In order to facilitate scientific research of bone marrow, the research community depends upon the long-term storage of bio-specimens, bio-fluids, stem cells, and bone marrow. Geneticist understands the sophisticated methods of cryopreservation to maintain the viability of stem cell products for the purpose of research. (7) Our laboratory professionals are also able to handle the logistics of getting the samples delivered in such a way that it doesn’t disturb the integrity of the bio-product. 

References and Further Reading

1. [Online] https://www.nature.com/bmt/.

2. [Online] https://biospecimens.cancer.gov/bestpractices/to/bcpsrd.asp.

3. [Online] https://www.sciencedaily.com/terms/bone_marrow.htm.

4. [Online] https://link.springer.com/article/10.1007/s00018-019-03125-1.

5. [Online] https://www.medicalnewstoday.com/articles/285666.php.

6. [Online] https://www.niddk.nih.gov/health-information/blood-diseases/aplastic-anemia-myelodysplastic-syndromes.

7. [Online] https://bethematch.org/support-the-cause/donate-bone-marrow/join-the-marrow-registry/likelihood-you-will-donate/.

8. [Online] https://publons.com/journal/27172/journal-of-bone-marrow-research.

9. [Online] http://www.hcpro.com/HOM-57532-3631/Rules-Regulations-Guidelines-for-stem-cell-storage-and-collection.html.