Tumor necrosis factor‐α levels in long‐term marrow cultures from patients with aplastic anemia: modulation by granulocyte‐macrophage colony‐stimulating factor

Abstract

We have previously shown that the levels of hematopoietic progenitors in long-term marrow cultures (LTMC) from patients with aplastic anemia (AA) are drastically reduced, as compared to normal LTMC. We have also reported that when LTMC from AA patients are supplemented with recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) there is an increase in colony-forming cell (CFC) levels. However, such a stimulation is only transient and it is followed by an inhibition in CFC growth. Based on these observations, in the present study we have tested the hypothesis that the levels of tumor necrosis factor-a (TNF-a), an inhibitor of hematopoiesis, are increased in AA LTMC and that such levels are further increased after rhGM-CSF has been added to the cultures for several weeks. Accordingly, we have determined the levels of TNF-a in the supernatant of LTMC established from normal (n = 8) and AA (n = 6) bone marrow and in AA LTMC supplemented with rhGM-CSF (n = 6). At the time of culture initiation, TNF-a levels were below detection in all the samples analyzed. After 5 weeks of culture, TNF-a levels in normal LTMC were very low, with a median of 7.3 pg/mL. In contrast, AA LTMC contained higher levels of TNF-a (median of 49.6 pg/mL). In keeping with our hypothesis, addition of rhGM-CSF to AA LTMC resulted in a signi®cant further increase of TNF-a levels (median of 135.4 pg/mL). Our results demonstrate an inverse correlation between reduced hematopoiesis in AA LTMC and increased levels of TNF-a in this culture system. Based on the results presented here, together with previous reports indicating that TNF-a is a potent inducer of apoptosis in hematopoietic progenitor cells, it seems reasonable to suggest that TNF-a is implicated in the pathophysiology of AA. Am.

Altered Expression of Hematopoiesis Regulatory Molecules in Lipopolysaccharide-Induced Bone Marrow Mesenchymal Stem Cells of Patients with Aplastic Anemia

“…It is an important member of the hematopoietic cytokine family secreted by stromal and other cell types. Similar to our observation, elevated levels of G-CSF transcripts have been reported in BM stromal cells and their culture supernatants [ 21 , 22 ]. On the one hand, increased expression of G-CSF is considered to represent a compensatory supraphysiological response of BM-MSCs to boost reduced hematopoiesis in AA.…”

An intrinsic thyrotropin-mediated pathway of TNF-α production by bone marrow cells

“…Moreover, excessive levels of BM TNF-␣ are believed to be linked to hematopoietic failure of allogeneic BM transplantation, 17 and to be involved in the pathogenesis of aplastic anemia, particularly when combined with granulocyte-macrophage colony-stimulating factor (GM-CSF). 18 Developmentally, TNF-␣ has been reported to have stimulatory effects in interleukin 3 (IL-3)-and GM-CSF-supplemented cultures of human CD34 ϩ hematopoietic progenitor cells (HPCs) during short-term culture, 19 and to have inhibitory effects on long-term HPC cultures. 20 Other studies indicate that the inhibitory activity of TNF-␣ is mediated through the p55 TNFR and that this occurs primarily for the more mature HPC populations, whereas TNF-␣-mediated inhibitory effects are associated with the p75 TNFR on early HPCs.…”

Myelodysplasia‐associated autoimmunity: clinical and pathophysiologic concepts

“…Myelodysplastic syndrome shares some of the features of acquired AA, a disease with an established autoimmune pedigree. Both in AA and MDS, plasma TNFα and IFN‐γ levels are high and T‐cell‐mediated myelosuppression occurs [66,67]. Abnormal CD4 : CD8 ratios, increased activated cytotoxic T cells, as demonstrated by a higher percentage of CD8+ CD28– and CD8+ CD28–CD57+ cells, and skewing of the TCR VB CDR3 patterns have been detected in both diseases suggesting an autoimmune T‐cell‐mediated myelosuppression in both [43,68].…”