Saturday, April 19, 2025
4/19/2025
Regulation of hematopoietic stem cells under low oxygen tension - ABSTRACT Hematopoietic stem cells (HSCs) generate all mature blood cells while reproducing themselves in a process, namely self-renewal. Their presence in the bone marrow (BM), mobilized peripheral blood, and cord blood (CB) has allowed their utility in the treatment of both malignant and non-malignant hematopoietic diseases via transplantation. However, the rarity of HSCs and the difficulty of expanding them can be a limitation for their applications. Thus, a better mechanistic understanding of HSC regeneration that might contribute to their homing, engraftment, and self-renewal is vital to improving HSC-based therapies. In the bone marrow, HSCs reside in a microenvironment where the oxygen tension is low (1~5%). Previous work showed that the low oxygen tension (hypoxia) provides a metabolic niche to facilitate HSCs’ functionality in vivo or enhances HSC expansion in vitro. Our recent work from mouse BM cells revealed a significant loss of phenotypical and functional HSCs if harvested in ambient air (normoxia). In contrast, HSCs collected and processed under hypoxia demonstrated higher engraftment and self-repopulating capacity. While these findings are interesting, mechanisms behind this distinction are still poorly understood but have the potential to improve hematopoietic cell transplantation (HCT) and gene therapy. The central goal of this proposal is to understand the signaling and metabolic alterations in HSCs under hypoxic conditions and to explore the potential to manipulate these processes in normoxic conditions to improve HSC functionality. We hypothesize that hypoxia alters the expression of genes involved in regulating lysosomal function, mitochondrial integrity, and iron metabolism to support self-renewal and prevent oxidative damage or differentiation. We have three major aims. In Aim 1, we will determine how hypoxia activates TFE3, a master transcriptional factor for lysosomal biogenesis, to facilitate self-renewal. We will specifically focus on the upstream regulatory elements, such as amino acid availability, and the function of a few TFE3 targeted genes in this process. In Aim 2, we will determine the role of Rho-associated kinase 1 (ROCK1) in regulating mitochondrial fission, a process that is suppressed by hypoxia to prevent oxidative damage in HSCs. In Aim 3, we will explore the role of iron metabolism in driving oxidative damage and differentiation of HSCs, and how a hypoxic environment prevents these processes. In this aim, we are particularly interested in exploring iron chelator as a potential treatment to improve HCT.
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