Pilot investigation on the dose-dependent impact of irradiation on primary human alveolar osteoblasts in vitro

Abstract

Radiotherapy of head and neck squamous cell carcinoma can lead to long-term complications like osteoradionecrosis, resulting in severe impairment of the jawbone. Current standard procedures require a 6-month wait after irradiation before dental reconstruction can begin. A comprehensive characterization of the irradiation-induced molecular and functional changes in bone cells could allow the development of novel strategies for an earlier successful dental reconstruction in patients treated by radiotherapy. The impact of ionizing radiation on the bone-forming alveolar osteoblasts remains however elusive, as previous studies have relied on animal-based models and fetal or animal-derived cell lines. This study presents the first in vitro data obtained from primary human alveolar osteoblasts. Primary human alveolar osteoblasts were isolated from healthy donors and expanded. After X-ray irradiation with 2, 6 and 10 Gy, cells were cultivated under osteogenic conditions and analyzed regarding their proliferation, mineralization, and expression of marker genes and proteins. Proliferation of osteoblasts decreased in a dose-dependent manner. While cells recovered from irradiation with 2 Gy, application of 6 and 10 Gy doses not only led to a permanent impairment of proliferation, but also resulted in altered cell morphology and a disturbed structure of the extracellular matrix as demonstrated by immunostaining of collagen I and fibronectin. Following irradiation with any of the examined doses, a decrease of marker gene expression levels was observed for most of the investigated genes, revealing interindividual differences. Primary human alveolar osteoblasts presented a considerably changed phenotype after irradiation, depending on the dose administered. Mechanisms for these findings need to be further investigated. This could facilitate improved patient care by re-evaluating current standard procedures and investigating faster and safer reconstruction concepts, thus improving quality of life and social integrity.

The effects of high-dose radiation therapy on bone: a scoping review

“…Szymczyk et al [ 9 ] showed that the decrease in cell proliferation was due to cell death induction by the radiation caused by G2 cell cycle arrest and the resulting enhanced sensitivity to apoptotic factors. Amler et al [ 11 ] isolated human alveolar osteoblasts and expanded them into cell lines. These cell lines were irradiated with single fractions of 2, 6, or 10 Gy.…”

“…Multiple studies show that higher doses of RT decrease osteoblast function and viability [7][8][9][10][11]. For example, Matsumura et al [7] exposed the osteoblast-like cell line, MC3T3-E1, to doses of 1, 5, and the mineralized matrix of the bone.…”

High-specificity protection against radiation-induced bone loss by a pulsed electromagnetic field

“…Osteoblasts are highly sensitive to ionizing radiation. The growth, survival, and functional maturation of osteoblasts are markedly suppressed when the bone is exposed to radiation ( 14 , 15 ). Osteoblasts are also much more vulnerable to ionizing radiation than undifferentiated mesenchymal stem cells ( 16 ).…”