Mild traumatic brain injury (mTBI) is a common consequence of head injury but there are no recognized interventions to promote recovery of the brain. We previously showed that photobiomodulation (PBM) significantly reduced the number of apoptotic cells in adult rat hippocampal organotypic slice cultures. In this study, we first optimized PBM delivery parameters for use in mTBI, conducting cadaveric studies to calibrate 660 and 810 nm lasers for transcutaneous delivery of PBM to the cortical surface. We then used an in vivo weight drop mTBI model in adult rats and delivered daily optimized doses of 660, 810 nm, or combined 660/810 nm PBM. Functional recovery was assessed using novel object recognition (NOR) and beam balance tests, whilst histology and immunohistochemistry were used to assess the mTBI neuropathology. We found that PBM at 810, 660 nm, or 810/660 nm all significantly improved both NOR and beam balance performance, with 810 nm PBM having the greatest effects. Histology demonstrated no overt structural damage in the brain after mTBI, however, immunohistochemistry using brain sections showed significantly reduced activation of both CD11b+ microglia and glial fibrillary acidic protein (GFAP)+ astrocytes at 3 days post‐injury. Significantly reduced cortical localization of the apoptosis marker, cleaved caspase‐3, and modest reductions in extracellular matrix deposition after PBM treatment, limited to choroid plexus and periventricular areas were also observed. Our results demonstrate that 810 nm PBM optimally improved functional outcomes after mTBI, reduced markers associated with apoptosis and astrocyte/microglial activation, and thus may be useful as a potential regenerative therapy.

中文翻译：

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光生物调节可改善轻度创伤性脑损伤后的功能恢复


轻度创伤性脑损伤 （mTBI） 是头部受伤的常见后果，但没有公认的干预措施可以促进大脑恢复。我们之前表明，光生物调节 （PBM） 显着降低了成年大鼠海马器官型切片培养物中凋亡细胞的数量。在这项研究中，我们首先优化了用于 mTBI 的 PBM 递送参数，进行尸体研究以校准 660 和 810 nm 激光，以便将 PBM 经皮递送到皮质表面。然后，我们在成年大鼠中使用体内体重下降 mTBI 模型，并提供 660、810 nm 或联合 660/810 nm PBM 的每日优化剂量。使用新物体识别 （NOR） 和光束平衡测试评估功能恢复，同时使用组织学和免疫组化评估 mTBI 神经病理学。我们发现 810 、 660 nm 或 810/660 nm 的 PBM 都显着改善了 NOR 和光束平衡性能，其中 810 nm PBM 的效果最大。组织学显示 mTBI 后大脑没有明显的结构损伤，然而，使用脑切片的免疫组织化学显示 CD11b + 小胶质细胞和神经胶质纤维酸性蛋白 （GFAP）+ 星形胶质细胞的激活在受伤后 3 天显着减少。还观察到 PBM 处理后细胞凋亡标志物、裂解的 caspase-3 的皮质定位显着降低和细胞外基质沉积的适度减少，仅限于脉络丛和脑室周围区域。我们的结果表明，810 nm PBM 最佳地改善了 mTBI 后的功能结果，减少了与细胞凋亡和星形胶质细胞/小胶质细胞活化相关的标志物，因此可能作为一种潜在的再生疗法。