In Vitro Study of Ineffective Erythropoiesis in Thalassemia: Diverse Intrinsic Pathophysiological Features of Erythroid Cells Derived from Various Thalassemia Syndromes

Abstract

Defective hemoglobin production and ineffective erythropoiesis contribute to the pathophysiology of thalassemia syndromes. Previous studies in the field of erythropoiesis mainly focused on the severe forms of thalassemia, such as β-thalassemia major, while mechanisms underlying the pathogenesis of other thalassemia syndromes remain largely unexplored. The current study aimed to investigate the intrinsic pathophysiological properties of erythroid cells derived from the most common forms of thalassemia diseases, including α-thalassemia (hemoglobin H and hemoglobin H-Constant Spring diseases) and β-thalassemia (homozygous β0-thalassemia and β0-thalassemia/hemoglobin E diseases), under an identical in vitro erythroid culture system. Cell proliferation capacity, differentiation velocity, cell death, as well as globin synthesis and the expression levels of erythropoiesis modifying factors were determined. Accelerated expansion was found in erythroblast cells derived from all types of thalassemia, with the highest degree in β0-thalassemia/hemoglobin E. Likewise, all types of thalassemia showed limited erythroid cell differentiation, but each of them manifested varying degrees of erythroid maturation arrest corresponding with the clinical severity. Robust induction of HSP70 transcripts, an erythroid maturation-related factor, was found in both α- and β-thalassemia erythroid cells. Increased cell death was distinctly present only in homozygous β0-thalassemia erythroblasts and associated with the up-regulation of pro-apoptotic (Caspase 9, BAD, and MTCH1) genes and down-regulation of the anti-apoptotic BCL-XL gene.

Reticulocyte Antioxidant Enzymes mRNA Levels versus Reticulocyte Maturity Indices in Hereditary Spherocytosis, β-Thalassemia and Sickle Cell Disease

“…It is important to notice that β-thal had a similar reticulocyte maturity profile to HS, but the RPI was significantly lower (Table 1), denoting a noteworthy ineffective erythropoiesis [44][45][46]. The altered erythropoiesis may explain the observed similarity in circulating reticulocyte maturity between HS and β-thal patients, which was simultaneous with very different pattern in mRNA relative levels of the antioxidant enzymes (Figure 1F).…”

“…The β-thal patients showed the lowest mRNA levels among the pathologic groups (Figure 1A-E), presenting CAT, PRX2 and GAPDH mRNA levels similar to those of the control group. In β-thal, erythropoiesis is characterized by an early-stage enhanced erythroblast proliferation, in parallel with limited erythroid differentiation and increased apoptosis during the late stages of erythropoietic development [44][45][46]. It appears that when the erythroblasts are able to differentiate, they give rise to reticulocytes which present an mRNA profile closer to that of healthy individuals than to those of HS or SCD patients.…”