The effect of hyperbaric oxygen therapy on bone macroscopy, composition and biomechanical properties after ionizing radiation injury

BACKGROUND: Radiotherapy used in tumor treatment compromises vascularization of bone tissue. Hyperbaric oxygenation (HBO) increases oxygen availability and improves vascularization, minimizing the deleterious effects of ionizing radiation (IR). Therefore, the aim of this study was to evaluate HBO therapy effect on bone macroscopy, composition and biomechanical properties after IR damage. METHODS: Twenty male Wistar rats weighing 300 ± 20 g (10 weeks of age) were submitted to IR (30 Gy) to the left leg, where the right leg was not irradiated. After 30 days, ten animals were submitted to HBO therapy, which was performed daily for 1 week at 250 kPa for 90-min sessions. All animals were euthanized 37 days after irradiation and the tibia were separated into four groups (n = 10): from animals without HBO - right tibia Non-irradiated (noIRnoHBO) and left tibia Irradiated (IRnoHBO); and from animals with HBO - right tibiae Non-irradiated (noIRHBO) and left tibia Irradiated (IRHBO). The length (proximal-distal) and thickness (anteroposterior and mediolateral) of the tibiae were measured. Biomechanical analysis evaluated flexural strength and stiffness. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) was used to calculate the amide I ratio, crystallinity index, and matrix to mineral ratios. RESULTS: In the macroscopic and ATR-FTIR analysis, the IRnoHBO showed lower values of length, thickness and amide I ratio, crystallinity index and matrix to mineral ratios compared to noIRnoHBO (p < 0.03). IRnoHBO showed no statistical difference compared to IRHBO for these analyses (p > 0.05). Biomechanics analysis showed that the IRnoHBO group had lower values of flexural strength and stiffness compared to noIRnoHBO and IRHBO groups (p < 0.04). In addition, the noIRHBO group showed higher value of flexural strength when compared to noIRnoHBO and IRHBO groups (p < 0.02). CONCLUSIONS: The present study concluded that IR arrests bone development, decreases the collagen maturation and mineral deposition process, thus reducing the flexural strength and stiffness bone mechanical parameters. Moreover, HBO therapy minimizes deleterious effects of irradiation on flexural strength and the bone stiffness analysis.