Yes, stem cells can be collected from blood, a procedure known as peripheral blood stem cell donation (PBSC). Stem cells are specialized, undifferentiated cells capable of developing into many different cell types, serving as the body’s repair system. Although stem cells are traditionally associated with bone marrow, a small number naturally circulate in the bloodstream. This allows for a non-surgical collection procedure, providing a viable alternative to the more invasive bone marrow harvest.
Hematopoietic Stem Cells: The Blood-Based Resource
The specific cells collected from the blood are Hematopoietic Stem Cells (HSCs), which are the source for all mature blood cells. HSCs reside primarily within the bone marrow, where they continuously perform hematopoiesis, or blood formation. These cells are multipotent, meaning they can differentiate into every type of cell found in the blood.
This includes red blood cells, white blood cells that form the immune system, and platelets necessary for clotting. A small fraction of these HSCs naturally enters the general circulation, forming the population referred to as peripheral blood stem cells. Collecting this circulating population provides the necessary cellular material for transplantation and other therapies.
How Stem Cells Are Moved Into the Bloodstream
The natural concentration of HSCs in the peripheral blood is too low for a successful collection, so the number of cells must be increased. This process, called mobilization, stimulates the bone marrow to release a higher volume of stem cells into the bloodstream. The most common method uses Granulocyte Colony-Stimulating Factor (G-CSF), a synthetic protein.
G-CSF is administered via daily subcutaneous injections for four to five days before collection. This growth factor increases the production of white blood cells and disrupts the cellular anchors holding HSCs in the marrow. This disruption forces a significant number of HSCs to move into the circulating peripheral blood where they can be collected.
This intentional release creates a temporary, harvestable concentration of stem cells. The mobilization phase can cause temporary side effects, most commonly flu-like symptoms, headaches, and mild to moderate bone pain due to the increased bone marrow activity.
The Apheresis Collection Procedure
Once the peripheral blood stem cell count is high enough, collection occurs using a non-surgical procedure called apheresis. The process is similar to donating plasma and is typically performed in an outpatient setting. The donor’s blood is drawn from a vein and flows into a specialized machine called a cell separator.
Inside the cell separator, the blood is spun in a centrifuge, separating components based on density. The machine isolates the layer containing the white blood cells and suspended HSCs, collecting them in a sterile bag. The remaining blood components, including red blood cells and plasma, are returned to the donor through a vein in the other arm.
The entire procedure usually takes between three to six hours per session. The process may need to be repeated on one or two consecutive days to collect the target number of stem cells.
Primary Medical Uses of Blood Stem Cells
The collected peripheral blood stem cells are used primarily in hematopoietic stem cell transplantation (HSCT). This procedure treats patients with blood cancers, such as leukemia, lymphoma, and multiple myeloma, or other blood disorders. High-dose chemotherapy and radiation destroy cancer cells but also destroy the patient’s bone marrow and immune system.
The healthy stem cells are then infused into the patient to rescue the blood-forming system. These transplanted HSCs travel to the bone marrow, where they engraft and restore the ability to produce new, healthy blood cells. Using peripheral blood stem cells is often preferred over traditional bone marrow harvest because it allows for faster recovery of the patient’s blood counts and yields a greater number of stem cells.