The expression of embryonic globin mRNA in a severely anemic mouse model induced by treatment with nitrogen-containing bisphosphonate.

Hirotada Otsuka,Jiro Takito,Naoko Nonaka,Nobuaki Yanagisawa,Hideki Yagi,Masanori Nakamura,Yasuo Endo,Satoshi Soeta

doi:10.1186/s12878-016-0041-0

Abstract

BackgroundMammalian erythropoiesis can be divided into two distinct types, primitive and definitive, in which new cells are derived from the yolk sac and hematopoietic stem cells, respectively. Primitive erythropoiesis occurs within a restricted period during embryogenesis. Primitive erythrocytes remain nucleated, and their hemoglobins are different from those in definitive erythrocytes. Embryonic type hemoglobin is expressed in adult animals under genetically abnormal condition, but its later expression has not been reported in genetically normal adult animals, even under anemic conditions. We previously reported that injecting animals with nitrogen-containing bisphosphonate (NBP) decreased erythropoiesis in bone marrow (BM). Here, we induced severe anemia in a mouse model by injecting NBP injection in combination with phenylhydrazine (PHZ), and then we analyzed erythropoiesis and the levels of different types of hemoglobin.MethodsSplenectomized mice were treated with NBP to inhibit erythropoiesis in BM, and with PHZ to induce hemolytic anemia. We analyzed hematopoietic sites and peripheral blood using morphological and molecular biological methods.ResultsCombined treatment of splenectomized mice with NBP and PHZ induced critical anemia compared to treatment with PHZ alone, and numerous nucleated erythrocytes appeared in the peripheral blood. In the BM, immature CD71-positive erythroblasts were increased, and extramedullary erythropoiesis occurred in the liver. Furthermore, embryonic type globin mRNA was detected in both the BM and the liver. In peripheral blood, spots that did not correspond to control hemoglobin were observed in 2D electrophoresis. ChIP analyses showed that KLF1 and KLF2 bind to the promoter regions of β-like globin. Wine-colored capsuled structures were unexpectedly observed in the abdominal cavity, and active erythropoiesis was also observed in these structures.ConclusionThese results indicate that primitive erythropoiesis occurs in adult mice to rescue critical anemia because primitive erythropoiesis does not require macrophages as stroma whereas macrophages play a pivotal role in definitive erythropoiesis even outside the medulla. The cells expressing embryonic hemoglobin in this study were similar to primitive erythrocytes, indicating the possibility that yolk sac-derived primitive erythroid cells may persist into adulthood in mice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12878-016-0041-0) contains supplementary material, which is available to authorized users.

Highlights

Mammalian erythropoiesis can be divided into two distinct types, primitive and definitive, in which new cells are derived from the yolk sac and hematopoietic stem cells, respectively
No changes were observed in hematocrit values and serum EPO levels in animals treated with splenectomy and nitrogen-containing bisphosphonate (NBP) alone compared to the values in the non-treatment group (Fig. 1b)
In splenectomized mice treated with PHZ, a significant reduction in hematocrit values was observed compared to controls and to animals treated with NBP alone (Fig. 1b)

Summary

Introduction

Mammalian erythropoiesis can be divided into two distinct types, primitive and definitive, in which new cells are derived from the yolk sac and hematopoietic stem cells, respectively. Mammalian hematopoiesis occurs in two distinct waves, commonly referred to as primitive and definitive, that originate in the yolk sac and in the fetal liver and bone marrow (BM), respectively [1]. Yolk sac-derived primitive erythroid cells remain nucleated and enucleated terminally in the circulation, whereas definitive erythroid cells produced in the fetal liver are released into circulation after complete maturation [2,3,4,5]. Definitive erythroid cells complete their maturation and enucleation at erythropoietic sites, the fetal liver and BM, where the adult complement of globin chains consists of α1-, α2- β1and β2- are expressed. All of the globin genes in the αand β-globin clusters are expressed in primitive erythroid cells, whereas definitive erythroid cells express only the adult globin genes [8]

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