Dissertation

Erythropoiesis: Injury and recovery

Peslak, Scott Alan

2012

Overview

Erythropoiesis is a robust process of cellular expansion and maturation that is required to maintain the massive steady-state red blood cell mass. However, anemia is common following clastogenic injury such as total body irradiation (TBI), suggesting that erythroid progenitors and precursors may be highly sensitive targets of radiation. Here, we explore the endogenous injury and recovery processes of the erythron following 4 Gy TBI of C57BL/6 mice. Functional colony assays were used to analyze erythroid progenitors, including day 7 burst-forming units (d7 BFU-E) and more mature d3 BFU-E and colony-forming units (CFU-E), and imaging flow cytometry was utilized to quantify erythroblast precursors, consisting of immature proerythroblasts and progressively more mature basophilic, polychromatophilic, and orthochromatic erythroblasts. We find that essentially all bone marrow and splenic erythroid progenitors and precursors are lost within two days following 4 Gy TBI. Phenotypic CFU-E and proerythroblasts in the bone marrow exhibit preferential apoptotic loss immediately following sublethal irradiation, revealing a functional transition at the proerythroblast to basophilic erythroblast maturational stages characterized by a shift from a pro-apoptotic to an anti-apoptotic phenotype. Following this initial loss, erythroid recovery is characterized by specific expansion of late-stage erythroid progenitors (d3 BFU-E and CFU-E) in the bone marrow that is dependent on endogenous erythropoietin (EPO) induction. This robust progenitor expansion is followed by a wave of maturing erythroid precursors in the bone marrow and their transient emergence in the bloodstream before re-initiation of extramedullary erythropoiesis in the spleen. Furthermore, we find that bone marrow macrophages, which constitute the erythroid precursor microenvironmental niche, are relatively radioresistant and form robust erythroblast islands post-4 Gy TBI during erythroid precursor recovery. We conclude that sublethal radiation serves as a model of endogenous stress erythropoiesis that is characterized by specific injury to the extravascular erythron, initial expansion and maturation of EPO-responsive late-stage progenitors exclusively in the bone marrow, and subsequent reseeding of extramedullary sites. This model will facilitate the study of mechanisms regulating erythropoiesis in bone marrow and extramedullary sites as well as the functional evaluation of erythroid lineage-directed therapeutics to mitigate cellular injury.

• Publisher: ProQuest Dissertations & Theses
• Subject: Cellular biology / Pathology
• ISBN: 9781267341594, 1267341599