Olive leaf components apigenin 7-glucoside and luteolin 7-glucoside direct human hematopoietic stem cell differentiation towards erythroid lineage

The generation of blood cellular components from hematopoietic stem cells is important for the therapy of a broad spectrum of hematological disorders. In recent years, several lines of evidence suggested that certain nutrients, vitamins and flavonoids may have important roles in controlling the stem cell fate decision by maintaining their self-renewal or stimulating the lineage-specific differentiation. In this study, main olive leaf phytochemicals oleuropein (Olp), apigenin 7-glucoside (Api7G) and luteolin 7-glucoside (Lut7G) were investigated for their potential effects on hematopoietic stem cell differentiation using both phenotypic and molecular analysis. Oleuropein and the combination of the three compounds enhanced the differentiation of CD34+ cells into myelomonocytic cells and lymphocytes progenitors and inhibited the commitment to megakaryocytic and erythroid lineages. Treatment with Lut7G stimulated both the erythroid and the myeloid differentiation, while treatment with Api7G specifically induced the differentiation of CD34+ cells towards the erythroid lineage and inhibited the myeloid differentiation. Erythroid differentiation induced by Api7G and Lut7G treatments was confirmed by the increase in hemoglobin genes expressions (α-hemoglobin, β-hemoglobin and γ-hemoglobin) and erythroid transcription factor GATA1 expression. As revealed by microarray analysis, the mechanisms underlying the erythroid differentiation-inducing effect of Api7G on hematopoietic stem cells involves the activation of JAK/STAT signaling pathway. These findings prove the differentiation-inducing effects of olive leaf compounds on hematopoietic stem cells and highlight their potential use in the ex vivo generation of blood cells.