Prolyl hydroxylase domain enzyme (PHD) inhibitors are effective in the treatment of chronic kidney disease (CKD)associated anemia by stabilizing hypoxia inducible factor (HIF), thereby increasing erythropoietin and consequently erythropoiesis. However, concern for CKD progression needs to be addressed in clinical trials. Although preclinical studies showed an anti-inflammatory effect in kidney disease models, the effect of PHD inhibitors on kidney fibrosis was inconsistent probably because the effects of HIF are cell type and context dependent. The major kidney erythropoietin-producing cells are pericytes that produce erythropoietin through HIF-2a-dependent gene transcription. The concern for the impact of HIF in pericytes on kidney fibrosis arises from the fact that pericytes are the major precursor cells of myofibroblasts in CKD. Since cells expressing Gli1 fulfill the morphologic and anatomic criteria for pericytes, we induced Gli1 þ cellspecific HIF stabilization or knockout to study the impact of HIF in pericytes on kidney pathology of mice with or without fibrotic injury induced by unilateral ureteral obstruction. Compared with the littermate controls, mice with pericyte-specific HIF stabilization due to von Hippel-Lindau protein or PHD2 knockout showed increased serum erythropoietin and polycythemia rather than a discernible difference in kidney fibrosis. Compared with Gli1 þ pericytes sorted from littermate controls, Gli1 þ pericytes sorted from PHD2 knockout mice showed increased erythropoietin gene expression rather than discernible changes in Col1a1 or Acta2 expression. Furthermore, pericyte-specific knockout of HIF-1a or HIF-2a did not affect kidney fibrosis. Thus, our study supports the absence of negative effects of PHD inhibitors on kidney fibrosis of mice despite HIF stabilization in pericytes.
Objective Macrophages are known to assist erythropoiesis. However, the effect of macrophage specific Vhl knockout on erythropoiesis is unclear. Methods We generated Tg(Csf1r-Cre/Esr1);VhlF/F mice to achieve inducible macrophage-specific Vhl knockout. Tg(Csf1r-Cre/Esr1);ROSA26CAG-tdTomato/+ was also generated to examine the knockout efficiency. Erythropoiesis was determined by analyses of complete blood count (CBC), spleen weight, and cell surface expression of TER-119 and CD71 in the bone marrow and spleen. Based on FSC-A and surface CD71 expression, we defined three different red blood cell (RBC) maturation stages as erythroblast, reticulocyte, and mature RBC. Stress erythropoiesis was induced by administration of recombinant human erythropoietin (rhEPO) 4U/gBW subcutaneously thrice per week for 6 doses. Results Tamoxifen administration in Tg(Csf1r-Cre/Esr1);ROSA26CAG-tdTomato/+ mice resulted in expression of tdTomato in CD11b(+)F4/80(+) cells in the spleen (79%) and peripheral blood mononuclear cell (PBMC) (48%). In steady state erythropoiesis, tamoxifen administration in Tg(Csf1r-Cre/Esr1);VhlF/F mice did not result in changes of CBC, spleen weight, ratio of TER-119(+) cells in live cells, or RBC maturation stages in the spleen and bone marrow. In stress erythropoiesis, administration of rhEPO resulted in polycythemia. However, no significant changes in Hct, ratio of TER-119(+) cells in live cells, or RBC maturation stages could be observed between Tg(Csf1r-Cre/Esr1);VhlF/F and littermate control mice after tamoxifen administration. Conclusion Macrophage specific knockout of Vhl in mice did not have significant effects on steady state erythropoiesis and rhEPO induced stress erythropoiesis.
Background and Aims Hypoxia-inducible factor prolyl hydroxylase inhibitor (HIF-PHI) activates HIF in renal pericytes and fibroblasts to promote erythropoietin production and erythropoiesis. However, the effects of HIF stabilization in the erythroid lineage are not clear. We aim to study the effects of erythroid lineage-specific stabilization of HIF on erythropoiesis by preclinical models. Method EporGFP-Cre/+;VhlF/F mice were used to achieve erythroid lineage-specific stabilization of HIF. Surface expression of TER-119, CD44, and forward scatter (FSC) were used to define erythroblast, reticulocyte, and red blood cell in the bone marrow. Expression of propidium iodide and surface annexin V were used to define apoptosis. Stress erythropoiesis was induced by subcutaneous administration of phenylhydrazine. Results Compared with littermate VhlF/F mice, EporGFP-Cre/+;VhlF/F mice had decreased hematocrit, decreased percentage of erythroblasts in the bone marrow, and increased apoptosis of erythroblasts in the bone marrow under steady state. These phenotypes of defective erythropoiesis were normalized in mice harboring concomitant Vhl, Hif1a, and Hif2a deletion (EporGFP-Cre/+;VhlF/F;Hif1aF/F;Hif2aF/Fmice). Although macrophages in the bone marrow also express Epor, macrophage-specific Vhl deletion in either Tg(Csf1r-CreESR1);VhlF/F or Lyz2Cre/+;VhlF/F mice did not result in defective erythropoiesis. During stress erythropoiesis, compared with littermate VhlF/F mice, EporGFP-Cre/+;VhlF/F mice had similar hematocrit, lower percentage of erythroblast in the bone marrow, and increased percentage of erythroblast in the spleen. Conclusion Vhl deletion in erythroid progenitor cells impairs erythropoiesis in murine bone marrow in the steady state. The phenotypes of defective erythropoiesis were partially reversed during stress erythropoiesis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.