Prostaglandin E₂ regulates murine hematopoietic stem/progenitor cells directly via EP4 receptor and indirectly through mesenchymal progenitor cells

Prostaglandin E₂ (PGE₂) regulates hematopoietic stem/progenitor cell (HSPC) activity. However, the receptor(s) responsible for PGE₂ signaling remains unclear. Here, we identified EP4 as a receptor activated by PGE₂ to regulate HSPCs. Knockdown of Ep4 in HSPCs reduced long-term reconstitution capacity, whereas an EP4-selective agonist induced phosphorylation of GSK3β and β-catenin and enhanced long-term reconstitution capacity. Next, we analyzed the niche-mediated effect of PGE₂ in HSPC regulation. Bone marrow mesenchymal progenitor cells (MPCs) expressed EP receptors, and stimulation ofMPCs with PGE₂ significantly increased their ability to support HSPC colony formation. Among the EP receptor agonists, only an EP4 agonist facilitated the formation of HSPC colonies after the coculture with MPCs. PGE₂ up-regulated the expression of cytokine-, cell adhesion-, extracellular matrix-, and protease-related genes in MPCs. We also examined the function of PGE₂/EP4 signaling in the recovery of the HSPCs after myelosuppression. The administration of PGE₂ or an EP4 agonist facilitated the recovery of HSPCs from 5-fluorouracil (5-FU)-induced myelosuppression, indicating a role for PGE₂/EP4 signaling in this process. Altogether, these data suggest that EP4 is a key receptor for PGE₂-mediated direct and indirect regulation of HSPCs.