Xu Zihan, Li Shengcan, Wan Liyang, Hu Jianzhong, Lu Hongbin, Zhang Tao
Department of Sports Medicine, Xiangya Hospital, Central South University, Changsha, China.
Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Xiangya Hospital, Central South University, Changsha, China.
J Orthop Res. 2023 May;41(5):919-929. doi: 10.1002/jor.25454. Epub 2022 Oct 17.
Low-intensity pulsed ultrasound (LIPUS) has been proven to accelerate the healing of the tendon-bone interface (TBI), and macrophages are considered to play an important regulatory role. This study was designed to explore the polarization of macrophages during treatment of TBI injury with LIPUS. In a rat model of rotator cuff tear, LIPUS or mock sonication (controls) was administered from 1 week postoperatively. The supraspinatus-supraspinatus tendon-humerus complexes were harvested for further evaluation at different time points for measures such as new bone formation, TBI maturity, ultimate failure load and stiffness, and types of macrophages. In vitro, bone marrow-derived macrophages were cultured, and polarization was identified after stimulation with or without LIPUS (the LIPUS or control groups, respectively). Two weeks posttreatment, the LIPUS group showed higher bone volume/total volume ratios and better TBI maturity scores. Six weeks posttreatment, the failure load of the LIPUS group was significantly higher than that of the control group. LIPUS also accelerated initial inflammatory macrophage accumulation and facilitated anti-inflammatory macrophage polarization (M2) in the late period. In the in vitro macrophage polarization model, the LIPUS group showed a higher proportion of M2 macrophages and mRNA expression of anti-inflammatory genes than the control group, while there was no significant difference in the proinflammatory macrophages between the two groups. Our observations revealed that macrophage polarization may be a potential mechanism of LIPUS treatment for TBI repair.
低强度脉冲超声（LIPUS）已被证明可加速肌腱-骨界面（TBI）的愈合，巨噬细胞被认为发挥着重要的调节作用。本研究旨在探讨LIPUS治疗TBI损伤过程中巨噬细胞的极化情况。在大鼠肩袖撕裂模型中，术后1周开始给予LIPUS或假超声处理（对照组）。在不同时间点采集冈上肌-冈上肌腱-肱骨复合体，以评估新骨形成、TBI成熟度、极限破坏载荷和刚度以及巨噬细胞类型等指标。在体外，培养骨髓来源的巨噬细胞，分别用LIPUS或不用LIPUS刺激后鉴定极化情况（分别为LIPUS组或对照组）。治疗2周后，LIPUS组的骨体积/总体积比值更高，TBI成熟度评分更好。治疗6周后，LIPUS组的破坏载荷显著高于对照组。LIPUS还加速了初期炎症巨噬细胞的聚集，并在后期促进了抗炎巨噬细胞极化（M2）。在体外巨噬细胞极化模型中，LIPUS组的M2巨噬细胞比例和抗炎基因的mRNA表达高于对照组，而两组之间促炎巨噬细胞无显著差异。我们的观察结果表明，巨噬细胞极化可能是LIPUS治疗TBI修复的潜在机制。
