Haematologica. 2017 Oct 27. pii: haematol.2017.172726. doi: 10.3324/haematol.2017.172726. [Epub ahead of print]

Erythropoietin inhibits osteoblast function in myelodysplastic syndromes via the canonical Wnt pathway.

Balaian E¹, Wobus M¹, Weidner H¹, Baschant U², Stiehler M³, Ehninger G¹, Bornhäuser M¹, Hofbauer LC³, Rauner M², Platzbecker U⁴.

Abstract

The effects of erythropoietin on osteoblasts and bone formation are controversially discussed. Since patients with myelodysplastic syndromes often display excessively high erythropoietin level, we aimed to analyze the effect of erythropoietin on osteoblast function in myelodysplastic syndromes and define the role of Wnt signaling in this process. Expression of osteoblast-specific genes and subsequent osteoblasts mineralization was increased in mesenchymal stromal cells from healthy young donors by in vitro erythropoietin treatment. However, erythropoietin failed to increase osteoblasts mineralization in old healthy donors and patients with myelodysplasia, whereas the basal differentiation potential of the latter was already significantly reduced compared to age-matched controls (p<0.01). This was accompanied by a significantly reduced expression of genes of the canonical Wnt pathway. Treatment of these cells with erythropoietin further inhibited the canonical Wnt pathway. Exposure of murine cells (C2C12) to erythropoietin also demonstrated a dose-dependent inhibition of TCF/LEF promoter activity (max. at 500 IU/ml, -2.8-fold, p<0.01). The decreased differentiation capacity of erythropoietin-pretreated mesenchymal stromal cells from patients with myelodysplasia could be restored by activating the Wnt pathway using lithium chloride or parathyroid hormone. Its hematopoiesis-supporting capacity was reduced, while reactivation of the canonical Wnt pathway in mesenchymal stromal cells could reverse this effect. Thus, these data demonstrate that erythropoietin modulates components of the osteo-hematopoietic niche in a context-dependent manner being anabolic in young, but catabolic in mature bone cells. Targeting the Wnt pathway in patients with myelodysplastic syndromes may be an appealing strategy to promote the functional capacity of the osteo-hematopoietic niche.