Effects of dexamethasone on erythroid colony and burst formation from human fetal liver and adult marrow

Polycythemia as the first manifestation of Cushing's disease

A 39-yr-old man presented to our hospital with unexplained erythrocytosis and hypertension. His follow-up for erythrocytosis had begun 2 yr earlier in another hospital and he had been diagnosed with polycythemia rubra vera. On admission to our hospital he was hypertensive (165/95 mmHg) and, except for the presence of moon-like face and facial plethora, his physical examination was normal. His hemoglobin concentration was 19.2 g/dl, and hematocrit was 58.9% with an increased red blood cell mass of 58 ml/kg as measured by radioisotope (Cr51). Blood film, other hematological indices except for elevated leukocyte alkaline phosphatase score, arterial gas analysis, and examination of aspirated bone marrow were all normal. An abdominal ultrasonography showed no evidence of splenomegaly. A diagnosis of probable secondary erythrocytosis was made. Early-morning serum cortisol and 24-h urinary free cortisol concentration as well as serum ACTH were high. Serum cortisol was not suppressed by low-dose dexamethasone, but suppressed by high-dose dexamethasone. Pituitary magnetic resonance imaging showed no lesion. After inferior petrosal sinus sampling suggesting right-central ACTH secretion, the patient underwent transnasal-transsphenoidal pituitary adenomectomy. Both hypercortisolemia and erythrocytosis regressed completely after the adenomectomy. After the operation, the patient's hemoglobin concentration and hematocrit decreased steadily, and 1 month post-adenomectomy his hemoglobin is 14.9 g/dl and hematocrit 44.8%. Thus, Cushing's syndrome should be a routine part of evaluation of unexplained polycythemia.

Dexamethasone facilitates erythropoiesis in murine embryonic stem cells differentiating into hematopoietic cells in vitro

Differentiating embryonic stem (ES) cells are increasingly emerging as an important source of hematopoietic progenitors with a potential to be useful for both basic and clinical research applications. It has been suggested that dexamethasone facilitates differentiation of ES cells towards erythrocytes but the mechanism responsible for sequential expression of genes regulating this process are not well-understood. Therefore, we in vitro induced differentiation of murine ES cells towards erythropoiesis and studied the sequential expression of a set of genes during the process. We hypothesized that dexamethasone-activates its cognate nuclear receptors inducing up-regulation of erythropoietic genes such as GATA-1, Flk-1, Epo-R, and direct ES cells towards erythropoietic differentiation. ES cells were cultured in primary hematopoietic differentiation media containing methyl-cellulose, IMDM, IL-3, IL-6, and SCF to promote embryoid body (EB) formation. Total RNA of day 3, 5, and 9-old EBs was isolated for gene expression studies using RT-PCR. Cells from day 9 EBs were subjected to secondary differentiation using three different cytokines and growth factors combinations: (1) SCF, EPO, dexamethasone, and IGF; (2) SCF, IL-3, IL-6, and TPO; and, (3) SCF IL-3, IL-6, TPO, and EPO. Total RNA from day 12 of secondary differentiated ES cells was isolated to study the gene expression pattern during this process. Our results demonstrate an up-regulation of GATA-1, Flk-1, HoxB-4, Epo-R, and globin genes (alpha-globin, betaH-1 globin, beta-major globin, epsilon -globin, and zeta-globin) in the 9-day-old EBs, whereas, RNA from 5-day-old EBs showed expression of HoxB-4, epsilon-globin, gamma-globin, betaH1-globin, and Flk-1. Three-day-old EBs showed only HoxB-4 and Flk-1 gene expression and lacked expression of all globin genes. These findings indicate that erythropoiesis-specific genes are activated later in the course of differentiation. Gene expression studies on the ES cells of secondary EB origin cultured in media containing dexamethasone showed a down-regulation of GATA-3 and an up-regulation of GATA-1, Flk-1, and Epo-R in comparison to the two other cytokines and growth factor combinations containing media. The secondary differentiation also showed an enhanced production of erythrocytic precursors in dexamethasone containing media in comparison to that in the control media. Our results indicate that dexamethasone can prove to be an effective agent which can be employed to enhance differentiation towards erythrocytic progenitors from ES cells.

HbF reactivation in sibling BFU-E colonies: synergistic interaction of kit ligand with low-dose dexamethasone

Mechanisms underlying fetal hemoglobin (HbF) reactivation in stress erythropoiesis have not been fully elucidated. We suggested that a key role is played by kit ligand (KL). Because glucocorticoids (GCs) mediate stress erythropoiesis, we explored their capacity to potentiate the stimulatory effect of KL on HbF reactivation, as evaluated in unilineage erythropoietic culture of purified adult progenitors (erythroid burst-forming units [BFU-Es]). The GC derivative dexamethasone (Dex) was tested in minibulk cultures at graded dosages within the therapeutical range (10(-6) to 10(-9) M). Dex did not exert significant effects alone, but synergistically it potentiated the action of KL in a dose-dependent fashion. Specifically, Dex induced delayed erythroid maturation coupled with a 2-log increased number of generated erythroblasts and enhanced HbF synthesis up to 85% F cells and 55% gamma-globin content at terminal maturation (ie, in more than 80%-90% mature erythroblasts). Equivalent results were obtained in unicellular erythroid cultures of sibling BFU-Es treated with KL alone or combined with graded amounts of Dex. These results indicate that the stimulatory effect of KL + Dex is related to the modulation of gamma-globin expression rather than to recruitment of BFU-Es with elevated HbF synthetic potential. At the molecular level, Id2 expression is totally suppressed in control erythroid culture but is sustained in KL + Dex culture. Hypothetically, Id2 may mediate the expansion of early erythroid cells, which correlates with HbF reactivation. These studies indicate that GCs play an important role in HbF reactivation. Because Dex acts at dosages used in immunologic disease therapy, KL + Dex administration may be considered to develop preclinical models for beta-hemoglobinopathy treatment.

Fetal hematopoietic stem cell transplantation: a challenge for the twenty-first century

Successful in utero hematopoietic stem cell transplantation will likely represent a major step forward in the management of patients with congenital hematological, metabolic, and immunological disorders. We review the naturally occurring models of hematopoietic chimerism in animals and humans, as well as available experimental animal data and human clinical attempts of fetal transplantation. Data available from naturally occurring models and experimental models of fetal transplantation suggest that this technique should be translatable to the human fetus. However, to date, the success of human fetal hematopoietic stem cell therapy has been limited to fetuses with severe immunologic defects. Evaluation of successful attempts of human transplantation, the ontogeny of fetal immune development, and data available from animals provide insights into innovative approaches to fetal therapy that may bring the reality of successful fetal transplantation closer.

The use of erythropoietin in neonates

Although much information has been accumulated about the clinical use of Epo in preterm infants, many questions remain unanswered. The evolution of clinical practice in the care of extremely ill, preterm infants continues to affect the number of transfusions required during hospitalization. Decreasing phlebotomy losses and instituting standardized transfusion guidelines have both been shown significantly to decrease the transfusion requirements of preterm infants. The administration of Epo likely decreases transfusion need even further; however, the direct impact of each of these actions has not been studied prospectively. It is likely that the combination of instituting rigorous and standardized transfusion guidelines, decreasing phlebotomy losses, and the appropriate use of Epo will have the greatest impact in decreasing transfusion requirements in all preterm and term neonates, regardless of the cause of their anemia.

In vitro effect of dexamethasone phosphate on hematopoietic progenitor cells in preterm infants

The in vitro effect of dexamethasone on the clonal growth of haematopoietic progenitors in preterm infants was investigated. Concentrations of 10(6)M to 10(9)M were associated with a dose dependent inhibition of colony formation, with the most clinically important effects seen on the earliest erythroid and granulocyte-macrophage colonies. Because of the potential clinical implications of these observations, studies are needed to determine the effects of dexamethasone on haematopoiesis in preterm infants.

A randomized, double-blind, placebo-controlled trial of recombinant erythropoietin in treatment of the anemia of bronchopulmonary dysplasia

Because anemia in patients with bronchopulmonary dysplasia is characterized by inappropriately low serum concentrations of erythropoietin but increased in vitro sensitivity of erythroid progenitors to erythropoietin, we speculated that administration of human recombinant erythropoietin would correct this anemia. Fifteen infants with the anemia of bronchopulmonary dysplasia were randomly assigned to receive erythropoietin or placebo subcutaneously for 10 days. Changes in reticulocyte count, hematocrit, blood lactate concentration, neutrophil count, platelet count, heart rate, oxygen requirement, weight gain, and number of transfusions were assessed. In the 10 erythropoietin recipients (99 +/- 12 days of age), hematocrit values increased from 0.325 +/- 0.006 to 0.381 +/- 0.013 (mean +/- SEM; p < 0.005) and reticulocyte counts from 122 +/- 20 to 446 +/- 48 x 10(3)/microliters (p < 0.005); lactate values remained unchanged. In the five placebo recipients (91 +/- 12 days of age), hematocrits and reticulocyte counts remained unchanged, and lactate values increased from 0.73 +/- 0.14 to 1.34 +/- 0.25 mumol/gm (p < 0.05). During the 30 days after the treatment period, one erythropoietin recipient and four placebo recipients were given transfusions. Other measured variables remained unchanged in both groups. We conclude that erythropoietin is effective in treatment of the anemia of bronchopulmonary dysplasia.

Modulation of human erythropoiesis by hydrocortisone in vitro

The effect of hydrocortisone on the formation of erythroid colonies was studied in vitro in cultures of normal human bone marrow in an agar system. A range of concentrations of hydrocortisone (10(-10) to 10(-3) mol/l) showed significant effects on erythroid burst formation, in terms of the number of colonies, on d 10 and 14 of culture. At subphysiological concentrations (10(-10) to 10(-8) mol/l), no effect was seen, but at both physiological (10(-7) mol/l) and pharmacological (10(-6) and 10(-5) mol/l) concentrations stimulation of erythroid burst formation was noted. At 10(-4) mol/l hydrocortisone inhibited erythroid colony formation and 10(-3) mol/l was uniformly lethal. In the concentration range of 10(-7) to 10(-5) mol/l hydrocortisone also appeared to increase erythroid colony size. Thus hydrocortisone (10(-7) to 10(-5) mol/l) stimulates erythroid colony growth and it is suggested that the hormone may play a role in the physiological regulation of human erythropoiesis.

Effect of aminoglutethimide on murine fetal hepatic erythroid colony formation

Pretreatment of pregnant mice with aminoglutethimide phosphate, an inhibitor of glucocorticoid synthesis, increases the content of fetal liver erythroid colony-forming cells (CFU-E), as assessed by the formation of erythroid colonies in vitro by fetal liver cells in plasma clots containing exogenous erythropoietin. In addition, the inability of aminoglutethimide to influence erythroid colony formation in vitro suggests that endogenous glucocorticoids exert a suppressive effect on the number of functional CFU-E in the fetal liver.