Interleukin-6 and its receptor are expressed by human megakaryocytes: in vitro effects on proliferation and endoreplication.
Interleukin-6 (IL-6) is a pleiotropic cytokine that plays an important role in the megakaryocytic differentiation. Recently, we have observed that IL-6 is synthesized by several human cell lines with megakaryocytic features. In this study, we have investigated whether a similar phenomenon occurs during normal megakaryocytic differentiation. Human megakaryocytes (MK) were obtained by culturing normal marrow in liquid culture with aplastic plasma (AP). First, an IL-6 secretion in bone marrow culture enriched in MK as well as in purified MK populations was demonstrated by a biologic assay. Second, IL-6 mRNA was detected in a purified population of MK by the polymerase chain reaction and dot blot analysis. IL-6 mRNA and protein were undetectable in platelets. Third, in situ hybridization procedure demonstrated the presence of IL-6 mRNA in individual immature MK. Fourth, IL-6 protein was detected in MK at the unicellular level by an immunoalkaline phosphatase technique using a monoclonal antibody against IL-6. Furthermore, the presence of IL-6 receptor (IL-6-R) on MK was demonstrated by in situ hybridization using an IL-6-R probe and in situ autoradiography after binding with [125I]-labeled recombinant IL-6. The IL-6 endogenously produced in liquid cultures containing normal human plasma or AP was subsequently neutralized. This resulted in a 50% decrease of the MK growth with a minor shift in the ploidy distribution toward lower values. In semisolid cultures the addition of anti-IL-6 antibodies led to a 42% decrease in colony number in cultures stimulated by IL-3 but not in other conditions of culture. These results suggest that normal human megakaryocytopoiesis might be regulated in part by an IL-6 autocrine loop.
Navarro
S
S
INSERM U91, Hôpital Henri Mondor, Créteil, France.
Debili
N
N
Le Couedic
J P
JP
Klein
B
B
Breton-Gorius
J
J
Doly
J
J
Vainchenker
W
W
D000911:Antibodies, Monoclonal; D001345:Autoradiography; D001854:Bone Marrow Cells; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics / Q000473:pathology; D015870:Gene Expression; D006801:Humans; D015151:Immunoblotting; D015850:Interleukin-6 / Q000235:genetics / Q000502:physiology*; D008533:Megakaryocytes / Q000473:pathology / Q000648:ultrastructure*; D009693:Nucleic Acid Hybridization; D011003:Ploidies; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011971:Receptors, Immunologic / Q000235:genetics / Q000502:physiology*; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology
D000911:Antibodies, Monoclonal; D015850:Interleukin-6; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins