Medical School of Chinese People's Liberation Army (PLA), Beijing, 100853, China.
Department of Stomatology, the First Medical Centre, Chinese PLA General Hospital, Beijing, 100853, China.
Mil Med Res. 2021 Dec 12;8(1):61. doi: 10.1186/s40779-021-00355-y.
The healing of bone defects can be challenging for clinicians to manage, especially after exposure to ionizing radiation. In this regard, radiation therapy and accidental exposure to gamma (γ)-ray radiation have been shown to inhibit bone formation and increase the risk of fractures. Cortical bone-derived stem cells (CBSCs) are reportedly essential for osteogenic lineages, bone maintenance and repair. This study aimed to investigate the effects of melatonin on postradiation CBSCs and bone defect healing.
CBSCs were extracted from C57BL/6 mice and were identified by flow cytometry. Then CBSCs were subjected to 6 Gy γ-ray radiation followed by treatment with various concentrations of melatonin. The effects of exogenous melatonin on the self-renewal and osteogenic capacity of postradiation CBSCs in vitro were analyzed. The underlying mechanisms involved in genomic stability, apoptosis and oxidative stress-related signaling were further analyzed by Western blotting, flow cytometry and immunofluorescence assays. Moreover, postradiation femoral defect models were established and treated with Matrigel and melatonin. The effects of melatonin on postradiation bone healing in vivo were evaluated by micro-CT and pathological analysis.
The decrease in radiation-induced self-renewal and osteogenic capacity were partially reversed in postradiation CBSCs treated with melatonin (P < 0.05). Melatonin maintained genomic stability, reduced postradiation CBSC apoptosis and intracellular oxidative stress, and enhanced expression of antioxidant-related enzymes (P < 0.05). Western blotting validated the anti-inflammatory effects of melatonin by downregulating interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) levels via the extracellular regulated kinase (ERK)/nuclear factor erythroid 2-related factor 2 (NRF2)/heme oxygenase-1 (HO-1) signaling pathway. Melatonin was also found to exhibit antioxidant effects via NRF2 signaling. In vivo experiments demonstrated that the newly formed bone in the melatonin plus Matrigel group had higher trabecular bone volume per tissue volume (BV/TV) and bone mineral density values with lower IL-6 and TNF-α levels than in the irradiation and the Matrigel groups (P < 0.05).
This study suggested that melatonin could protect CBSCs against γ-ray radiation and assist in the healing of postradiation bone defects.
骨缺损的愈合对临床医生来说是一个挑战，尤其是在接触电离辐射后。在这方面，放射治疗和意外接触伽马（γ）射线已被证明会抑制骨形成并增加骨折的风险。皮质骨源性干细胞（CBSCs）被报道对成骨谱系、骨维持和修复至关重要。本研究旨在探讨褪黑素对放射后 CBSCs 和骨缺损愈合的影响。
从 C57BL/6 小鼠中提取 CBSCs，并通过流式细胞术进行鉴定。然后，将 CBSCs 进行 6Gyγ 射线照射，再用不同浓度的褪黑素处理。分析外源性褪黑素对体外放射后 CBSCs 自我更新和成骨能力的影响。通过 Western blot、流式细胞术和免疫荧光法进一步分析涉及基因组稳定性、细胞凋亡和氧化应激相关信号的潜在机制。此外，建立放射后股骨缺损模型，并使用 Matrigel 和褪黑素进行治疗。通过 micro-CT 和病理分析评估褪黑素对体内放射后骨愈合的影响。
褪黑素处理部分逆转了放射诱导的 CBSCs 自我更新和成骨能力的下降（P<0.05）。褪黑素维持基因组稳定性，减少放射后 CBSC 凋亡和细胞内氧化应激，并增强抗氧化相关酶的表达（P<0.05）。Western blot 通过下调细胞外调节激酶（ERK）/核因子红细胞 2 相关因子 2（NRF2）/血红素加氧酶-1（HO-1）信号通路，验证了褪黑素的抗炎作用，降低了白细胞介素 6（IL-6）和肿瘤坏死因子 alpha（TNF-α）的水平。还发现褪黑素通过 NRF2 信号发挥抗氧化作用。体内实验表明，褪黑素加 Matrigel 组的新形成骨具有更高的组织体积骨体积比（BV/TV）和骨密度值，且白细胞介素 6 和肿瘤坏死因子 alpha 水平低于照射组和 Matrigel 组（P<0.05）。
本研究表明，褪黑素可以保护 CBSCs 免受γ射线辐射，并有助于放射后骨缺损的愈合。
