The Broad Spectrum of Cytokine Gene Expression by Myoid Cells from the Human Marrow Microenvironment

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Abstract
Nontransformed stromal colony-derived cell lines (CDCLs) consist of a pure stromal cell population that differentiates following a vascular smooth muscle cell repertoire, and whose in vivo counterpart is that of myoid cells found in adult and fetal human bone marrow cords. We studied the cytokine expression by reverse-transcriptase polymerase chain reaction (RT-PCR) from pooled fast-growing clones from 10 different bone marrow samples. RT-PCR indicated that 30 cytokines (out of 42 studied) were expressed by CDCLs (20 after medium renewal and hydrocortisone renewal, three after addition of interleukin 1β (IL-1β) and seven in only part of the CDCL layers examined). The cytokines expressed comprised mediators known to be involved in the maintenance of early and late hematopoiesis (IL-1α and IL-β, IL-6, IL-7, IL-8, IL-11 and IL-13; colony-stimulating factors, thrombopoietin, erythropoietin, stem cell factor, flt 3-ligand, hepatocyte cell growth factor, tumor necrosis factor α, leukemia inhibitory factor, transforming growth factors β1 and β3; and macrophage inflammatory protein 1α), angiogenic factors (fibroblast growth factors 1 and 2, vascular endothelial growth factor) and mediators whose usual target (and source) is the connective tissue-forming cells (platelet-derived growth factor A, epidermal growth factor, transforming growth factors α and β2, oncostatin M and insulin-like growth factor 1), or neuronal cells (nerve growth factor). The cytokines not expressed were lymphokines (IL-2, IL-3, IL-4, IL-5, IL-9, IL-10, and IL-12 and interferon γ) or mediators synthesized by macrophages (inhibin, activin, platelet-derived growth factor B, and IL-1 receptor antagonist). This study complements the description of the phenotype of the myoid cells, confirming that these cells are the marrow connective tissue-forming cells; moreover, this work suggests that stromal control of hematopoiesis is multifactorial and that myoid cells are involved in the control of marrow angiogenesis and innervation.