title: Type beta transforming growth factor is a potent inhibitor of murine megakaryocytopoiesis in vitro.
abstract: To investigate the potential role of platelets in the inhibition of megakaryocytopoiesis, freeze-thawed extracts of human platelets were added to serumless liquid cultures of murine marrow. When acetylcholinesterase (AchE), a marker of megakaryocytic differentiation in mice, was assayed, a significant inhibition of enzymatic activity was noted in cultures containing the equivalent of greater than 5 X 10(6) solubilized platelets per milliliter. Freeze-thawed extracts of granulocytes had significantly less inhibitory effect than did platelets. Transforming growth factor beta (TGF-beta), a growth factor known to be inhibitory to some cell lineages and to be found at relatively high concentrations in platelets, was then added to liquid marrow cultures. A similar inhibition of AchE activity was detected when cultures were stimulated with mitogen-stimulated conditioned medium. The effect was potent with 50% inhibition of AchE activity observed at 4 pmol TGF-beta/L. To determine if TGF-beta inhibited specifically one aspect of megakaryocytic differentiation, the factor was added to isolated single megakaryocytes in serumless culture induced by interleukin 3 (IL3) to increase in size. The number of megakaryocytes increasing in size in response to IL 3 exposure was reduced from 68% to 20% when both factors were simultaneously added to cultures. Colony assays showed that megakaryocytic and granulocyte-macrophage colony detection was inhibited at picomolar concentrations of the factor. These data suggest that TGF-beta is a potent in vitro inhibitor of the murine megakaryocytic lineage, although its effects are not limited to this lineage.
authors.forename: T
authors.initials: T
authors.lastname: Ishibashi
authors.forename: S L
authors.initials: SL
authors.lastname: Miller
authors.forename: S A
authors.initials: SA
authors.lastname: Burstein
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D003114:Colony-Forming Units Assay; D006133:Growth Substances / Q000494:pharmacology; D006410:Hematopoiesis / Q000187:drug effects; D006801:Humans; D008533:Megakaryocytes / Q000502:physiology*; D051379:Mice; D010455:Peptides / Q000502:physiology*; D015291:Transforming Growth Factors
chemical_list: D006133:Growth Substances; D010455:Peptides; D015291:Transforming Growth Factors; D000110:Acetylcholinesterase