Recombinant Human Interleukin-11 Directly Promotes Megakaryocytopoiesis In Vitro

Abstract

We have investigated the mechanism of action of the thrombopoietic cytokine, recombinant human interleukin-11 (rhIL-11), on megakaryocytopoiesis in vitro. We have shown that rhIL-11–induced murine and human megakaryocytopoiesis are not mediated by thrombopoietin (Tpo). Murine megakaryocytes (MKs) were produced from bone marrow (BM) mononuclear cells cultured with rhIL-11, IL-3, and a combination of the two cytokines. Conditioned media (CM) were collected and assayed for the presence of biologically active Tpo. Tpo activity was not detected in any of the CMs tested. Next, human BM CD34+ cells were cultured in serum-free fibrin clot medium with rhIL-11, IL-3, or rhIL-11 plus IL-3 and an antibody that neutralizes human Tpo activity. No inhibition of either burst-forming unit-MK– or colony-forming unit-MK–derived colony formation was observed. The antibody did partially inhibit steel factor-induced MK-colony formation, suggesting that the actions of this cytokine are mediated, in part, by Tpo. We determined that MKs can be direct targets of rhIL-11 by showing the expression of functional IL-11 receptor on these cells. Total RNA was prepared from cultured human BM CD41+CD14− cells (MKs) and IL-11 receptor α chain mRNA was detected in the MKs by reverse transcription-polymerase chain reaction. Analysis of single-sorted CD41+CD14− cells confirmed that the observed IL-11 receptor expression was not due to contaminating CD41− cells in the pool. The presence of rhIL-11 receptor α chain protein in the cells was established by Western blot analysis. After a short exposure of purified BM MKs to rhIL-11, enhanced phosphorylation of both its signal transduction subunit, gp130, and the transcription factor, STAT3 was detected, showing a direct activation of receptor signaling by the cytokine. Consistent with the lack of effect of rhIL-11 on platelets in vivo, IL-11 receptor α chain mRNA and protein were not detected in isolated human platelets. These data indicate that rhIL-11 acts directly on MKs and MK progenitors but not on platelets.

Review article: pharmacological approaches for the treatment of thrombocytopenia in patients with chronic liver disease and hepatitis C infection

“…When IL-11 receptors are stimulated by ligand binding (Figure 2a), they undergo phosphorylation and activate the STAT3 transcription factor. 54 IL-11 promotes megakaryocyte maturation, stimulates platelet production in normal animals, and can enhance haematopoietic recovery following myelosuppression. In mice, IL-11 increased megakaryocyte ploidy in the bone marrow and megakaryocyte colony-forming units (CFUs) in the spleen.…”

“…10,[55][56][57][58] Interestingly, the IL-11 receptor is not present on platelets. 54 Clinically, recombinant human IL-11 (rhIL-11; oprelvekin) has been successful in some patients. In a phase I study in advanced breast cancer patients treated with myelosuppressive chemotherapy, treatment with rhIL-11 produced dose-dependent increases in bone marrow progenitor cells, megakaryocytes and mean platelet counts.…”

Platelet growth factors: potential impact on transfusion medicine

“…It is encoded by a single gene on chromosome 19 and is normally produced in bone marrow stromal cells. Receptors for IL‐11 are found on a large number of cell types, including osteoblasts, osteoclasts, intestinal crypt cells, oral mucosa cells, B‐lymphocytes, and megakaryocytes, but not in platelets 23–25 …”

“…IL‐11. Although IL‐11 was initially found to stimulate proliferation of an IL‐6‐dependent murine plasmacytoma line, 23–25 subsequent work showed that it had a wide range of activities, often in combination with other hematopoietic growth factors. IL‐11 promoted the growth of immunoglobulin‐secreting B cells in vitro.…”

Regulatory effects of interleukin-11 during acute lung inflammatory injury

“…Interleukin-11 (IL-11) was originally identified as a stromal cell product that stimulated proliferation of IL-6-dependent plasmacytoma cells [1]. Subsequent studies have demonstrated that IL-11 has effects similar to IL-6, including megakaryocyte proliferation [2] and induction of acute phase response proteins [3]. Functional similarities between IL-6 and IL-11 can be explained by the fact that signal transduction for both of these cytokines is mediated through the transmembrane glycoprotein 130 (gp130) receptor component, which is common to both IL-6 and IL-11 receptor complexes [4,5].…”