Molecular Aspects of Bone Resorption in β-Thalassemia Major

Abstract

β-thalassemia is the most common single gene disorder worldwide, in which hemoglobin β-chain production is decreased. Today, the life expectancy of thalassemic patients is increased because of a variety of treatment methods; however treatment related complications have also increased. The most common side effect is osteoporosis, which usually occurs in early adulthood as a consequence of increased bone resorption. Increased bone resorption mainly results from factors such as delayed puberty, diabetes mellitus, hypothyroidism, ineffective hematopoiesis as well as hyperplasia of the bone marrow, parathyroid gland dysfunction, toxic effect of iron on osteoblasts, growth hormone (GH) and insulin-like growth factor-1 (IGF-1) deficiency. These factors disrupt the balance between osteoblasts and osteoclasts by interfering with various molecular mechanisms and result in decreased bone density. Given the high prevalence of osteopenia and osteoporosis in thalassemic patients and complexity of their development process, the goal of this review is to evaluate the molecular aspects involved in osteopenia and osteoporosis in thalassemic patients, which may be useful for therapeutic purposes.

Keywords: Bone Marrow; Bone Resorption; Osteoblasts; Osteoclasts; β-thalassemia.

Fig.1

Important molecules involved in bone resorption in thalassemia. TGF-β; Transforming growth factor-beta, SOST; Sclerostin, DKK-1; Dickkopf, BMP2; Bone morphogenetic protein-2, GH; Growth hormone, IGF-1; Insulin-like growth factor-1, Wnt; Wingless related protein, LRP5; Low density lipoprotein (LDL)-related protein 5, OPG; Osteoprotegrin, RANKL; Activator of NF-κB receptor ligand, TNF-α; Tumor necrotic factor-alpha, IL-6; Interlukin-6, IL-1α; Interlukin-1 alpha and COLIA1; Collagen type I alpha 1 gene.