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Platelet factor 4 inhibits human megakaryocytopoiesis in vitro
Z C Han1, L Sensébe, J F Abgrall
1Department of Hematology, Augustin Morvan Hospital, Brest University School of Medicine, France.
Abstract:
Platelet factor 4 (PF4) is a multifunctional protein specific to platelets, synthesized in megakaryocytes and stored in alpha granules. This report of our work shows that PF4 potently inhibits human megakaryocyte colony formation in vitro. Colony formation by megakaryocyte progenitor cells from normal bone marrows was studied using the plasma clot culture system and indirect immunoperoxidase staining. Nonadherent mononuclear cells were co-cultured with various concentrations (0 to 20 micrograms/mL) of highly purified human PF4. Statistically significant inhibition of three classes of megakaryocyte progenitor cells, the mixed colony forming unit-megakaryocytes (mCFU-MK), the burst forming unit-megakaryocytes (BFU-MK), and the colony forming unit-megakaryocytes (CFU-MK), was seen at a PF4 concentration of 2.5 micrograms/mL or greater. PF4 had no effect on erythroid (BFU-E) and granulocyte/macrophage (CFU-GM) colony formation except at high concentration (5 micrograms/mL for BFU-E and 10 micrograms/mL for CFU-GM). When a concentration of 5 micrograms/mL PF4 was added at various time points during marrow culture, a reduction of megakaryocyte colony formation also occurred. In the presence of PF4 2.5 micrograms or 5 micrograms/mL, the percentage of mature type of colonies was found to be decreased compared with cultures with no added PF4. These data demonstrate that PF4 inhibits both proliferation and maturation of megakaryocyte progenitor cells in vitro and suggest that PF4 may play a role in autoregulating human megakaryocytopoiesis.
Insights
Platelet factor 4 (PF4) significantly inhibits megakaryocyte progenitor cell proliferation and maturation in vitro. These findings suggest PF4 plays a role in regulating human megakaryocytopoiesis.
Area of Science:
- Hematology
- Cell Biology
- Molecular Medicine
Background:
- Platelet factor 4 (PF4) is a protein synthesized by megakaryocytes and stored in platelet alpha granules.
- PF4 is known to have diverse biological functions beyond hemostasis.
Purpose of the Study:
- To investigate the effect of PF4 on human megakaryocyte progenitor cell colony formation in vitro.
- To determine if PF4 influences the proliferation and maturation of megakaryocyte progenitor cells.
Main Methods:
- Human bone marrow mononuclear cells were cultured with varying concentrations of purified human PF4.
- Megakaryocyte progenitor cells (mCFU-MK, BFU-MK, CFU-MK) were assessed using plasma clot culture and indirect immunoperoxidase staining.
- Erythroid (BFU-E) and granulocyte/macrophage (CFU-GM) progenitor cells were also evaluated.
Main Results:
- PF4 significantly inhibited mCFU-MK, BFU-MK, and CFU-MK formation at concentrations of 2.5 µg/mL and above.
- PF4 demonstrated minimal impact on BFU-E and CFU-GM colony formation except at higher concentrations.
- Addition of PF4 during culture reduced megakaryocyte colony formation and decreased the percentage of mature colonies.
Conclusions:
- PF4 potently inhibits both the proliferation and maturation of human megakaryocyte progenitor cells in vitro.
- These results suggest a potential role for PF4 in the autoregulation of human megakaryocytopoiesis.