The Primary Study of CD90(+)CD34(-)and Sca-1(+) Stem Cells Mobilized by EPO Plus G-CSF in Mice

Erythropoietin in bone homeostasis-Implications for efficacious anemia therapy

Bone homeostasis and hematopoiesis are irrevocably linked in the hypoxic environment of the bone marrow. Erythropoietin (Epo) regulates erythropoiesis by binding to its receptor, Epor, on erythroid progenitor cells. The continuous process of bone remodeling is achieved by the finely balanced activity of osteoblasts in bone synthesis and osteoclasts in bone resorption. Both osteoblasts and osteoclasts express functional Epors, but the underlying mechanism of Epo‐Epor signaling in bone homeostasis is incompletely understood. Two recent publications have provided new insights into the contribution of endogenous Epo to bone homeostasis. Suresh et al examined Epo‐Epor signaling in osteoblasts in bone formation in mice and Deshet‐Unger et al investigated osteoclastogenesis arising from transdifferentiation of B cells. Both groups also studied bone loss in mice caused by exogenous human recombinant EPO‐stimulated erythropoiesis. They found that either deletion of Epor in osteoblasts or conditional knockdown of Epor in B cells attenuates EPO‐driven bone loss. These findings have direct clinical implications because patients on long‐term treatment for anemia may have an increased risk of bone fractures. Phase 3 trials of small molecule inhibitors of the PHD enzymes (hypoxia inducible factor‐prolyl hydroxylase inhibitors [HIF‐PHIs]), such as Roxadustat, have shown improved iron metabolism and increased circulating Epo levels in a titratable manner, avoiding the supraphysiologic increases that often accompany intravenous EPO therapy. The new evidence presented by Suresh and Deshet‐Unger and their colleagues on the effects of EPO‐stimulated erythropoiesis on bone homeostasis seems likely to stimulate discussion on the relative merits and safety of EPO and HIF‐PHIs.

Vascular Wall as Source of Stem Cells Able to Differentiate into Endothelial Cells

The traditional view of the vascular biology is changed by the discovery of vascular progenitor cells in bone marrow or peripheral blood Further complexity is due to the findings that the vessel walls harbor progenitor and stem cells, called vascular wall-resident vascular stem cells (VW-VSCs), able to differentiate to mature vascular wall cells. These immature stem/progenitor cell populations and multipotent mesenchymal lineage participate in postnatal neovascularization and vascular wall remodeling. Further studies are necessary to deepen the knowledge on characterization and biology of VW-VSCs, in particular of endothelial progenitor cells (EPCs) in order to improve their use in clinical settings for regenerative approaches.

Pleiotropic effects of Erythropoietin. Influence of Erythropoietin on processes of mesenchymal stem cells differentiation

Structure and synthesis of Erythropoietin: Erythropoietin (EPO) is a glycoprotein hormone.

Recombinant Erythropoietin (Epoetin): Human recombinant erythropoietin is characterised as a factor which stimulates differentiation and proliferation of erythroid precursor cells, and as a tissue protective factor.

Anti-ischemic effects of recombinant Erythropoietin: Erythropoietin is one of the most perspective humoral agents which are involved in the preconditioning phenomenon.

Erythropoietin receptors and signal transduction pathways: Erythropoietin effects on cells through their interconnection with erythropoietin receptors, which triggers complex intracellular signal cascades, such as JAK2/STAT signaling pathway, phosphatidylinositol 3-kinase (PI3K), protein kinase C, mitogen-activated protein kinase (MAPK), and nuclear factor (NF)-κB signaling pathways.

Mechanisms of the effect of Erythropoietin on hematopoietic and non-hematopoietic cells and tissues: In addition to regulation of haemopoiesis, erythropoietin mediates bone formation as it has an effect on hematopoietic stem cells and osteoblastic niche, and this illustrates connection between the processes of haematopoiesis and osteopoiesis which take place in the red bone marrow.

The effect of Erythropoietin on mesenchymal stem cells and process of bone tissue formation: Erythropoietin promotes mesenchymal stem cells proliferation, migration and differentiation in osteogenic direction. The evidence of which is expression of bone phenotype by cells under the influence of EPO, including activation of bone specific transcription factors Runx2, osteocalcin and bone sialoprotein.

Conclusion: Erythropoietin has a pleiotropic effect on various types of cells and tissues. But the mechanisms which are involved in the process of bone tissue restoration via erythropoietin are still poorly understood.

Modulation of stem cell differentiation with biomaterials

Differentiation of stem cells can be controlled with interactions with microenvironments of the stem cells. The interactions contain various signals including soluble growth factor signal, cell adhesion signal, and mechanical signal, which can modulate differentiation of stem cells. Biomaterials can provide these types of signals to induce desirable cellular differentiation. Biomaterials can deliver soluble growth factors locally to stem cells at a controlled rate for a long period. Stem cell adhesion to specific adhesion molecules presented by biomaterials can induce specific differentiation. Mechanical signals can be delivered to stem cells seeded onto biomaterial scaffolds. These approaches would be invaluable for direction of stem cell differentiation and in vivo tissue regeneration using stem cells.

Effect of Recombinant Human Erythropoietin On the Stemness of Bone Marrow-derived Mesenchymal Stem Cells in vitro

The purpose of this study was to investigate the effects of the recombinant human erythropoietin (rhEPO) on proliferative and multi-differentiation potential of the bone marrow-derived mesenchymal stem cells (MSCs). The MSCs were isolated primarily from bone marrow of adult rat and purified at increasing passage. A purified population of MSCs can be obtained about 2 weeks after the initiation of culture. After three passages (P3-MSCs), bone marrow-derived adherent cells were identified, then different concentrations of rhEPO (0.1, 1, 5, 10, 100 U/ml) was added into the Passage-3 cells which had been identified. The expression of the surface markers in adherent cells was detected by the flow cytometry. The mRNA levels of transcription factors OCT4, SOX2, Nanog and TERT were measured by reverse transcription-polymerase chain reaction (RT-PCR). The results showed that CD29 and CD90 were positive in MSCs, but not CD33, CD44 and CD45, and the cells could differentiate into multiple lineages such as osteocytes and adipocytes. The expression of OCT4, SOX2, TERT, Nanog mRNA were up-regulated by the treatment of EPO. The effect of EPO was the most obvious when its concentration was 5U/mL after 12h. we conclude that MSCs can not only perserve characteristics of stem cells but also maintain its multi-lineage differentiation potential after appropriate treatment of EPO.