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Heme oxygenase-1 deletion affects stress erythropoiesis.

Cao YA, Kusy S, Luong R, Wong RJ, Stevenson DK, Contag CH - PLoS ONE (2011)

Bottom Line: Here, we describe the specific effects of HO-1 deficiency on stress erythropoiesis.In the spleens of mice that received hmox(+/-) cells, we show (i) decreases in the proerythroblast, basophilic, and polychromatophilic erythroblast populations; (ii) increases in the insoluble iron levels and decreases in the soluble iron levels; (iii) increased numbers of Mac-1(+)-cells expressing TNF-α; and (iv) decreased levels of CD49d expression in the basophilic and polychromatophilic erythroblast populations.As reflected by effects on secreted and cell surface proteins, HO-1 deletion likely affects stress erythropoiesis through the retention of erythroblasts in the erythroblastic islands of the spleen.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America.

ABSTRACT

Background: Homeostatic erythropoiesis leads to the formation of mature red blood cells under non-stress conditions, and the production of new erythrocytes occurs as the need arises. In response to environmental stimuli, such as bone marrow transplantation, myelosuppression, or anemia, erythroid progenitors proliferate rapidly in a process referred to as stress erythropoiesis. We have previously demonstrated that heme oxygenase-1 (HO-1) deficiency leads to disrupted stress hematopoiesis. Here, we describe the specific effects of HO-1 deficiency on stress erythropoiesis.

Methodology/principal findings: We used a transplant model to induce stress conditions. In irradiated recipients that received hmox(+/-) or hmox(+/+) bone marrow cells, we evaluated (i) the erythrocyte parameters in the peripheral blood; (ii) the staining intensity of CD71-, Ter119-, and CD49d-specific surface markers during erythroblast differentiation; (iii) the patterns of histological iron staining; and (iv) the number of Mac-1(+)-cells expressing TNF-α. In the spleens of mice that received hmox(+/-) cells, we show (i) decreases in the proerythroblast, basophilic, and polychromatophilic erythroblast populations; (ii) increases in the insoluble iron levels and decreases in the soluble iron levels; (iii) increased numbers of Mac-1(+)-cells expressing TNF-α; and (iv) decreased levels of CD49d expression in the basophilic and polychromatophilic erythroblast populations.

Conclusions/significance: As reflected by effects on secreted and cell surface proteins, HO-1 deletion likely affects stress erythropoiesis through the retention of erythroblasts in the erythroblastic islands of the spleen. Thus, HO-1 may serve as a therapeutic target for controlling erythropoiesis, and the dysregulation of HO-1 may be a predisposing condition for hematologic diseases.

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HO-1 participates in proper erythroblast differentiation.(A) Representative FACS profiles of freshly isolated BM cells (left panels) and splenic cells (right panels) from hmox+/+ or hmox+/− BM cell recipients at day 15 post-transplantation are shown. Cells were labeled with PE-conjugated anti-CD71 and PE-Cy7-conjugated anti-Ter119. Dead cells (stained positive with propidium iodide) and enucleated erythrocytes (with low forward scatter) were excluded from the analysis. The regions (from left to right and then from top to bottom) distinctly differentiate four classes of erythroid precursors (from the earlier to the most mature): proerythroblasts (Ter119medCD71high) in region a, basophilic erythroblasts (Ter119highCD71high) in region b, late basophilic and polychromatophilic erythroblasts (Ter119highCD71med) in region c, and orthochromatophilic erythroblasts (Ter119highCD71low) in region d. The engraftment of HO-1-deficient BM cells modifies the FACS profile of the erythroblastic BM and splenic cells. (B) The frequencies of total erythroid precursors found in regions a, b, c and d in the BM and the spleens of hmox+/+ or hmox+/− BM cell recipients are shown. The transplantation of HO-1-deficient BM cells leads to a decrease in the erythroid precursor population. The mean ± SEM is shown for six mice per genotype; *P≤0.05.
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pone-0020634-g002: HO-1 participates in proper erythroblast differentiation.(A) Representative FACS profiles of freshly isolated BM cells (left panels) and splenic cells (right panels) from hmox+/+ or hmox+/− BM cell recipients at day 15 post-transplantation are shown. Cells were labeled with PE-conjugated anti-CD71 and PE-Cy7-conjugated anti-Ter119. Dead cells (stained positive with propidium iodide) and enucleated erythrocytes (with low forward scatter) were excluded from the analysis. The regions (from left to right and then from top to bottom) distinctly differentiate four classes of erythroid precursors (from the earlier to the most mature): proerythroblasts (Ter119medCD71high) in region a, basophilic erythroblasts (Ter119highCD71high) in region b, late basophilic and polychromatophilic erythroblasts (Ter119highCD71med) in region c, and orthochromatophilic erythroblasts (Ter119highCD71low) in region d. The engraftment of HO-1-deficient BM cells modifies the FACS profile of the erythroblastic BM and splenic cells. (B) The frequencies of total erythroid precursors found in regions a, b, c and d in the BM and the spleens of hmox+/+ or hmox+/− BM cell recipients are shown. The transplantation of HO-1-deficient BM cells leads to a decrease in the erythroid precursor population. The mean ± SEM is shown for six mice per genotype; *P≤0.05.

Mentions: The spleen and BM serve as reserves for accelerated hematopoiesis under conditions of hematopoietic stress. Loss of HO-1 did not change the total spleen and BM cellularities (data not shown). To further investigate whether HO-1 deficiency specifically affects stress erythropoiesis, we adopted a flow cytometric assay and analyzed cells from the BM and spleen of transplanted mice. Four classes of erythroid precursors can be identified by the staining intensities (low, medium (med), or high) of specific surface markers upon maturation, as shown in Figure 2 and as previously described [15]. Listed in order of the earliest to the most mature, these precursors are the early proerythroblast (Ter119medCD71high) identified in region a, the basophilic erythroblast (Ter119highCD71high) in region b, the late basophilic and polychromatophilic erythroblast (Ter119highCD71med) in region c, and the orthochromatophilic erythroblast (Ter119highCD71low) in region d.


Heme oxygenase-1 deletion affects stress erythropoiesis.

Cao YA, Kusy S, Luong R, Wong RJ, Stevenson DK, Contag CH - PLoS ONE (2011)

HO-1 participates in proper erythroblast differentiation.(A) Representative FACS profiles of freshly isolated BM cells (left panels) and splenic cells (right panels) from hmox+/+ or hmox+/− BM cell recipients at day 15 post-transplantation are shown. Cells were labeled with PE-conjugated anti-CD71 and PE-Cy7-conjugated anti-Ter119. Dead cells (stained positive with propidium iodide) and enucleated erythrocytes (with low forward scatter) were excluded from the analysis. The regions (from left to right and then from top to bottom) distinctly differentiate four classes of erythroid precursors (from the earlier to the most mature): proerythroblasts (Ter119medCD71high) in region a, basophilic erythroblasts (Ter119highCD71high) in region b, late basophilic and polychromatophilic erythroblasts (Ter119highCD71med) in region c, and orthochromatophilic erythroblasts (Ter119highCD71low) in region d. The engraftment of HO-1-deficient BM cells modifies the FACS profile of the erythroblastic BM and splenic cells. (B) The frequencies of total erythroid precursors found in regions a, b, c and d in the BM and the spleens of hmox+/+ or hmox+/− BM cell recipients are shown. The transplantation of HO-1-deficient BM cells leads to a decrease in the erythroid precursor population. The mean ± SEM is shown for six mice per genotype; *P≤0.05.
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Related In: Results  -  Collection

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pone-0020634-g002: HO-1 participates in proper erythroblast differentiation.(A) Representative FACS profiles of freshly isolated BM cells (left panels) and splenic cells (right panels) from hmox+/+ or hmox+/− BM cell recipients at day 15 post-transplantation are shown. Cells were labeled with PE-conjugated anti-CD71 and PE-Cy7-conjugated anti-Ter119. Dead cells (stained positive with propidium iodide) and enucleated erythrocytes (with low forward scatter) were excluded from the analysis. The regions (from left to right and then from top to bottom) distinctly differentiate four classes of erythroid precursors (from the earlier to the most mature): proerythroblasts (Ter119medCD71high) in region a, basophilic erythroblasts (Ter119highCD71high) in region b, late basophilic and polychromatophilic erythroblasts (Ter119highCD71med) in region c, and orthochromatophilic erythroblasts (Ter119highCD71low) in region d. The engraftment of HO-1-deficient BM cells modifies the FACS profile of the erythroblastic BM and splenic cells. (B) The frequencies of total erythroid precursors found in regions a, b, c and d in the BM and the spleens of hmox+/+ or hmox+/− BM cell recipients are shown. The transplantation of HO-1-deficient BM cells leads to a decrease in the erythroid precursor population. The mean ± SEM is shown for six mice per genotype; *P≤0.05.
Mentions: The spleen and BM serve as reserves for accelerated hematopoiesis under conditions of hematopoietic stress. Loss of HO-1 did not change the total spleen and BM cellularities (data not shown). To further investigate whether HO-1 deficiency specifically affects stress erythropoiesis, we adopted a flow cytometric assay and analyzed cells from the BM and spleen of transplanted mice. Four classes of erythroid precursors can be identified by the staining intensities (low, medium (med), or high) of specific surface markers upon maturation, as shown in Figure 2 and as previously described [15]. Listed in order of the earliest to the most mature, these precursors are the early proerythroblast (Ter119medCD71high) identified in region a, the basophilic erythroblast (Ter119highCD71high) in region b, the late basophilic and polychromatophilic erythroblast (Ter119highCD71med) in region c, and the orthochromatophilic erythroblast (Ter119highCD71low) in region d.

Bottom Line: Here, we describe the specific effects of HO-1 deficiency on stress erythropoiesis.In the spleens of mice that received hmox(+/-) cells, we show (i) decreases in the proerythroblast, basophilic, and polychromatophilic erythroblast populations; (ii) increases in the insoluble iron levels and decreases in the soluble iron levels; (iii) increased numbers of Mac-1(+)-cells expressing TNF-α; and (iv) decreased levels of CD49d expression in the basophilic and polychromatophilic erythroblast populations.As reflected by effects on secreted and cell surface proteins, HO-1 deletion likely affects stress erythropoiesis through the retention of erythroblasts in the erythroblastic islands of the spleen.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America.

ABSTRACT

Background: Homeostatic erythropoiesis leads to the formation of mature red blood cells under non-stress conditions, and the production of new erythrocytes occurs as the need arises. In response to environmental stimuli, such as bone marrow transplantation, myelosuppression, or anemia, erythroid progenitors proliferate rapidly in a process referred to as stress erythropoiesis. We have previously demonstrated that heme oxygenase-1 (HO-1) deficiency leads to disrupted stress hematopoiesis. Here, we describe the specific effects of HO-1 deficiency on stress erythropoiesis.

Methodology/principal findings: We used a transplant model to induce stress conditions. In irradiated recipients that received hmox(+/-) or hmox(+/+) bone marrow cells, we evaluated (i) the erythrocyte parameters in the peripheral blood; (ii) the staining intensity of CD71-, Ter119-, and CD49d-specific surface markers during erythroblast differentiation; (iii) the patterns of histological iron staining; and (iv) the number of Mac-1(+)-cells expressing TNF-α. In the spleens of mice that received hmox(+/-) cells, we show (i) decreases in the proerythroblast, basophilic, and polychromatophilic erythroblast populations; (ii) increases in the insoluble iron levels and decreases in the soluble iron levels; (iii) increased numbers of Mac-1(+)-cells expressing TNF-α; and (iv) decreased levels of CD49d expression in the basophilic and polychromatophilic erythroblast populations.

Conclusions/significance: As reflected by effects on secreted and cell surface proteins, HO-1 deletion likely affects stress erythropoiesis through the retention of erythroblasts in the erythroblastic islands of the spleen. Thus, HO-1 may serve as a therapeutic target for controlling erythropoiesis, and the dysregulation of HO-1 may be a predisposing condition for hematologic diseases.

Show MeSH
Related in: MedlinePlus