Identification of MDM2 as a novel gene marker and key regulator of radiation-induced osteoblast damage

Introduction: Bone injury is a common side effect and a long-term response in radiotherapy-induced osteoblast damage, often characterized by reduced osteoblast proliferation and differentiation. Despite its clinical relevance, studies on radiation-induced bone injury are limited, and the molecular mechanisms underlying ionizing radiation (IR)-induced osteoblast damage remain largely unclear. Objectives: This study aimed to establish a radiation-induced osteoblast injury model, screen and identify related factors involved in the radiation injury of osteoblasts. Methods: The optimal IR damage conditions were first determined by measuring cell proliferation, cycle, apoptosis, and differentiation and mineralization abilities in a radiation-induced osteoblast injury model. Subsequently, differentially expressed genes were screened through RNA sequencing of radiation-damaged MC3T3-E1 cells. Results: Mouse double minute 2 homolog (MDM2) was the most significantly upregulated gene post-IR treatment, suggesting its key role in responses to IR. Meanwhile, cell apoptosis, cell cycle regulation, and several pathways, including the phosphoinositide 3-kinase/protein kinase B signaling pathway and signaling pathways involved in the cell cycle, were enriched. Furthermore, the role of MDM2 in radiation-induced osteoblast proliferation, differentiation, and DNA damage was investigated, followed by the identification of key pathway alterations under conditions of MDM2 knockdown and IR treatment. Conclusion: MDM2 knockdown alleviated IR damage in MC3T3-E1 cells by promoting cell proliferation, reducing cell cycle arrest and apoptosis rates, and reversing osteoblast differentiation. These effects may be due to the alleviation of DNA damage.