TGF-beta1 drives and accelerates erythroid differentiation in the epo-dependent UT-7 cell line even in the absence of erythropoietin.
OBJECTIVE
TGF-beta1 is a powerful inhibitor of erythropoiesis. However, its mechanisms of action are not fully elucidated yet at the cellular level. In this work we have studied the effects of TGF-beta on UT-7 cell survival, proliferation and differentiation.


METHODS
UT-7 cell line is strictly dependent on growth factors for cell survival, growth, and differentiation. Epo (2 U/mL) induces erythroid differentiation as assessed by up regulation of glycophorin A and the presence of 5%-10% benzidine positive cells (BPC). In contrast, even in the presence of Epo (2 U/mL), GM-CSF (1 ng/mL) inhibits erythroid differentiation.


RESULTS
When UT-7 cells were switched from GM-CSF to Epo, TGF-beta1 (2 ng/mL) induced a rapid (3 days [Epo+TGF-beta1] vs 8 days [Epo]) and marked erythroid differentiation (80% [Epo+TGF-beta1] vs 10% [Epo] BPC) including Hemoglobin A synthesis (HbA/HbF ratio of 1 [Epo] vs 4 [Epo+TGF-beta1]). In the presence of GM-CSF, although to a lesser extent, TGF-beta1 induced erythroid differentiation (40% BPC). This effect was not a consequence of TGF-beta1-induced apoptosis because, in the presence of Epo or GM-CSF, apoptosis occurred only at day 8 or 10, respectively. Moreover, although SCF inhibited apoptotic effect of TGF-beta1, SCF+TGF-beta1+Epo was the best combination to give rise to the highest number of hemoglobinized cells. We further demonstrated that induction of erythroid differentiation by TGF-beta1 was not due to an autocrine loop involving Epo/Epo-R or to a prolongation of the G1 phase of the cell cycle.


CONCLUSIONS
Taken together, these data suggest that TGF-beta1 is an inducer of erythroid differentiation, even stronger than Epo at the cellular level.
Zermati
Y
Y
CNRS UMR 8603 and IFR Necker, Université René Descartes (Paris V), Paris, France.
Varet
B
B
Hermine
O
O
D002454:Cell Differentiation / Q000187:drug effects; D004900:Erythroblasts / Q000187:drug effects* / Q000473:pathology*; D004920:Erythropoiesis / Q000187:drug effects*; D004921:Erythropoietin / Q000494:pharmacology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D016212:Transforming Growth Factor beta; D004921:Erythropoietin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor