The Role of Other Hemopoietic Growth Factors and the Marrow Microenvironment in Megakaryocytopoiesis

The recent identification, purification, and cloning of thrombopoietin (TPO), a lineage-specific regulator of platelet production, is the culmination of several decades of research dealing with the regulation of megakaryocytopoiesis (1–5) . Although endogenous TPO plays a pivotal role in promoting the proliferation and maturation of megakaryocytc progenitor cells and megakaryocytes, a considerable amount of data exists that indicates that other growth factors are also capable of altering this finely regulated biological process (6,7) . These non-TPO regulatory factors are capable not only of promoting megakaryocytc proliferation and maturation, but also of downregulating these cellular processes (6,7). These growth factors might play an important role in the physiological regulation of megakaryocytopoiesis and may be instrumental in the pathogenesis of a number of clinical syndromes (8–12) . In addition, recombinant forms of these growth factors have considerable potential in the treatment of clinical disorders of thrombopoiesis (7) . These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.