Effect of X-Ray Irradiation on Proliferation and Differentiation of Osteoblast

Abstract

We exposed the osteoblast-like cell line, MC3T3-E1, to 1-to 10-Gy X-ray. Irradiation at doses of 5-Gy dose or stage, confluence, and post-proliferation stages. The alkaline phosphatase activity, conversely, was increased by irradiation, and the calcium content of irradiated cells was greater than that of nonirradiated. These findings suggest that irradiation induces terminal differentiation and calcification of osteoblasts.

Injectable calcium phosphate scaffold and bone marrow graft for bone reconstruction in irradiated areas: An experimental study in rats

“…These results agree with those of Arnold et al on irradiated bone [23]. Spontaneous bone repair is highly compromised and reduced in irradiated areas and the physiology of bone repair is modified after radiation therapy [21,[24][25][26]. Ionizing radiation delays fracture union, increases the incidence of fibrous union [26], induces osteoradionecrosis [7] and adversely reduces the quality of bone grafts [8].…”

“…Ionizing radiation delays fracture union, increases the incidence of fibrous union [26], induces osteoradionecrosis [7] and adversely reduces the quality of bone grafts [8]. The compromised features of irradiated bone repair are due to the cellular effects of ionizing radiation; osteoblasts and osteoclasts are quantitatively decreased with radiotherapy [24,25]; terminal differentiation of osteoblasts is accelerated [24]. Marrow stroma is also damaged by radiation exposure [27].…”

X-ray radiation at low doses stimulates differentiation and mineralization of mouse calvarial osteoblasts

“…The levels of DNA synthesis were measured by [methyl- 3 H] thymidine deoxyribose (TdR; Amersham Pharmacia Biotech Inc., Piscataway, NJ, USA) incorporation assay. In brief, cells grown in 96-multiwell plates were treated with 1 μCi TdR/well at 3 days post-irradiation and then processed for an additional 12 h incubation.…”

“…Numerous studies have attempted to determine the mechanisms by which irradiation affects bone differentiation and mineralization. Considerable findings have shown that irradiation leads to detrimental effects on cells, as evidenced by decreased viability and/or DNA synthesis in bone-like (3)(4)(5), leukemia (6), and mesenchymal stromal cells (7). Irradiation also results in single or double-stranded DNA breaks and eventually blocks cell cycle progression (6).…”

“…However, there is a great controversy on the actual effects of irradiation on bone, in which irradiation stimulates osteoblast differentiation (5,8). This stimulation appears to be associated with increasing the levels of bone-specific regulatory markers such as alkaline phosphatase (ALP), transforming growth factor-beta 1 (TGF-β1), and runt-related transcription factor 2 (Runx2) (3,8,9). mRNA expression of bone differentiation-related proteins, such as type I collagen (COL I), osteocalcin (OCN), and osteopontin (OPN), is dynamically affected by irradiation, and the resulting effects differ according to the quantity of radiation employed and the times of testing after irradiation (5,10,11).…”