The regulation of megakaryocyte and platelet production

Thrombopoietin, a hormone that regulates blood platelet production, is now recognized to be an important in vivo hematopoietic stimulator. In this concise review, the background on thrombopoietin, development of assays, and identification of sources of the hormone are summarized, along with brief descriptions of other controlling factors, sites of thrombopoietin production, results of producing antibodies against the factor, sites of action of thrombopoietin both in vitro and in vivo, and its effect on blood platelet production. Suitable assays and stable sources of thrombopoietin have now been identified and their development will permit production of recombinant material. Once the gene is cloned, it is expected that recombinant thrombopoietin will be invaluable for treating patients with several platelet production problems.