Preclinical Study of Pain Neuropeptide Expression in Murine Sensory Neurons Induced by Irradiated Osteoclasts in the Context of Stereotactic Body Radiation Therapy.

Stereotactic body radiation therapy (SBRT) for lung tumors near the chest wall often causes significant chest wall pain (CWP), negatively impacting patients' quality of life. The mechanisms behind SBRT-induced CWP remain unclear and may involve multiple factors. We investigated crosstalk between radiation-activated osteoclasts and sensory neurons, focusing on osteoclast-derived factors in CWP. Using murine pre-osteoclast cell line Raw264.7, we induced differentiation with Receptor Activator of Nuclear Factor kappa-beta Ligand (RANKL), followed by 10 Gy gamma-irradiation. Conditioned media (C.M) from irradiated osteoclasts was used to treat sensory neuronal cultures from mouse dorsal root ganglia. Neuronal cultures were also exposed to 10 Gy radiation, with and without osteoclast co-culture. Osteoclast markers and pain-associated neuropeptides were analyzed using RT-qPCR and histochemical staining. Osteoclasts differentiation and activity were inhibited using osteoprotegerin (OPG) and risedronate. High-dose radiation significantly increased the size of tartrate-resistant-acid-phosphatase (TRAP)-positive osteoclasts (1.36-fold) and activity biomarkers (, 1.35-fold, , 1.76-fold). Neurons treated with C.M from irradiated osteoclasts showed ~1.5-fold increase in (calcitonin gene-related peptide) and (substance P) expression, which was mitigated by osteoclast inhibitors. These findings suggest that radiation enhances osteoclast activity and promotes pain signaling. Osteoclast inhibitors may represent a therapeutic strategy to reduce CWP and improve quality of life.