Summary
Highlights
Adult stem cells are unique, unspecialized, and self-renewing cells primarily produced in the bone marrow. A small number circulate the body, aiding in normal repair and defense.
Stromal cells and osteoblasts in the bone marrow produce SDF1, a chemotactic protein that attracts stem cells. Endothelial cells also release SDF1, creating a gradient that interacts with CXCR4 on stem cells, holding them within the bone marrow and preventing their release into the peripheral blood.
To collect adult stem cells, they must be prompted to enter the peripheral blood using Granulocyte Colony Stimulating Factor (GCSF). GCSF activates enzymes like neutrophil elastase, cathepsin G, and MMP9, which cleave SDF1 and inhibit its interaction with CXCR4. Additionally, CD26 protein on some stem cells also cleaves SDF1.
When the SDF1-CXCR4 interaction is blocked, stem cells are no longer confined to the bone marrow and can move into the peripheral blood. Once circulating, these stem cells can be harvested through a process called apheresis.