Regulation of stress erythropoiesis via splenic erythroid microenvironment development and metabolic programming

Open Access
- Author:
- Hao, Siyang
- Graduate Program:
- Molecular, Cellular and Integrative Biosciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 31, 2019
- Committee Members:
- Robert F. Paulson, Dissertation Advisor/Co-Advisor
Zhi-Chun Lai, Committee Chair/Co-Chair
K. Sandeep Prabhu, Committee Member
Andrew D. Patterson, Committee Member
Xiaojun (Lance) Lian, Outside Member - Keywords:
- stress erythropoiesis
splenic erythroid niche
cellular metabolism
growth-differentiation factor 15
glucocorticoids
Yes-associated protein - Abstract:
- Stress erythropoiesis is a tightly regulated physiological process to rapidly generate new erythrocytes in response to anemic stress. Functional studies focusing on regulatory signaling pathways involved in this process provide new insights into the development of effective treatments for various types of anemias. Application of advanced technologies in transcriptomics, proteomics and metabolomics analyses enable a more comprehensive understanding of key nodes that regulate the proliferation and differentiation of committed erythroid progenitors, promote the establishment of supportive erythroid microenvironment, and govern nutrient availability through metabolic programming. In this dissertation, by using well-established in vivo and in vitro murine stress erythropoiesis models, the function and mechanism of three signals in regulating stress erythropoiesis were investigated in three related projects. The first project aims to address the role of growth-differentiation factor 15 (Gdf15), a member of transforming growth factor-beta (Tgf-), in regulating erythroid recovery from anemic stress. We demonstrate that Gdf15 is required for stress erythropoiesis in vivo and in vitro. In the spleen, Gdf15 promotes the monocyte-derived expansion of the splenic niche, in part by maintaining the hypoxia-dependent expression of the niche signal, bone morphogenetic protein 4 (Bmp4). Lack of Gdf15 signaling results in impaired proliferation of stress erythroid progenitors and production of stress burst forming unit-erythroid cells. While in stress erythroid progenitors, Gdf15 signaling regulates the expression of metabolic enzymes including Pdk1/3 and Gls1, which contribute to the rapid proliferation of stress erythroid progenitors. Collectively, this study reveals the key role of Gdf15 signaling as a comprehensive regulator that coordinates the stress erythroid microenvironment with the metabolic status of progenitors to promote stress erythropoiesis. The second project focuses on a class of anti-inflammatory hormones, glucocorticoids (GCs). We demonstrate that synthesis of GCs by murine adrenal glands is induced prior to the kidney producing EPO in response to phenylhydrazine-induced hemolysis and during the recovery from bone marrow transplant following lethally irradiation suggesting a regulatory role of GCs in recovery from anemic stress. Analysis of monocyte-specific mutation of glucocorticoid receptor (GR) provides new insights into GR-mediated differentiation of monocytes into macrophages. Furthermore, our data suggest a novel role of GC/GR signaling in regulation of metabolic reprograming associated with altered glucose metabolic pathways along erythroid differentiation. In the third project, a novel role of Yes-associated protein (Yap), the downstream transcriptional coactivator of Hippo pathway, in regulating a specialized stress erythroid progenitor population during stress erythropoiesis. Function of Yap has been intensively studied in promoting cell growth, stem cell maintenance, and tissue homeostasis in various types of tissues, but not in erythroid lineage of cells. Our data indicate that in vivo, Yap-mutated erythroid progenitors fail to expand in the spleen upon transplantation to lethally irradiated recipient mice. Additionally, loss of Yap impairs the growth of actively proliferating erythroid progenitors in vitro, which is supported by gene expression profiles showing that transiently amplifying stress erythroid progenitors express high levels of genes associated with Yap activity and genes induced by Yap. Moreover, we demonstrate that Yap promotes the proliferation of stress erythroid progenitors in part by regulating the expression of key glucose- and glutamine-metabolizing enzymes. Taken together, my studies introduce a comprehensive understanding of stress erythropoiesis which is regulated at the level of stress erythroid progenitors regarding controls of cell proliferation and differentiation, and at the level of stress erythroid niche concerning the development and expansion of cells in the splenic microenvironment in concert with regulations mediated by nutrient resources and cellular metabolism.