22.7 : Role of Hematopoietic Growth Factors

Hematopoietic growth factors are a group of regulatory and signaling molecules that influence the differentiation of hematopoietic stem cells, or HSCs.

Erythropoietin, or EPO, is a hormone produced primarily by the kidneys and is directly involved in producing erythrocytes.

A low blood oxygen level triggers EPO release into the bloodstream, which reaches the bone marrow, stimulating the hematopoietic stem cells to differentiate and mature into erythrocytes for oxygen transport.

Thrombopoietin, or TPO, is the second essential growth factor primarily released by the liver.

TPO works by stimulating the proliferation and maturation of megakaryocytes into platelets to help with blood clotting and wound healing.

Cytokines are small signaling glycoproteins involved in hematopoiesis. Interleukins and colony-stimulating factors, or CSFs, are the two essential classes of cytokines regulating the maturation of different blood cells.

The interleukins can act on specific cell types like interleukin-2, which stimulates T-cell proliferation, or interleukin-3, which works on granulocytes, megakaryocytes, and erythroid precursors.

The granulocyte CSF enhances the growth and maturation of granular leukocytes.