School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, GA 30332, USA.
Acta Biomater. 2023 Sep 15;168:277-285. doi: 10.1016/j.actbio.2023.07.009. Epub 2023 Jul 13.
Duchenne muscular dystrophy (DMD) causes patients to suffer from ambulatory disability and cardiorespiratory failure, the latter of which leads to premature death. Due to its role in respiration, the diaphragm is an important muscle for study. A common method for evaluating diaphragm function is ex vivo force testing, which only allows for an end point measurement. In contrast, ultrasound shear wave elastography imaging (US-SWEI) can assess diaphragm function over time; however, US-SWEI studies in dystrophic patients to date have focused on the limbs without preclinical studies. In this work, we used US-SWEI to estimate the shear wave speed (SWS) in diaphragm muscles of healthy (WT) mice, mdx mice, and mdx mice haploinsufficient for utrophin (mdx-utr) at 6 and 12 months of age. Diaphragms were then subjected to ex vivo force testing and histological analysis at 12 months of age. Between 6 and 12 months, a 23.8% increase in SWS was observed in WT mice and a 27.8% increase in mdx mice, although no significant difference was found in mdx-utr mice. Specific force generated by mdx-utr diaphragms was lower than that of WT diaphragms following twitch stimulus. A strong correlation between SWS and collagen deposition was observed, as well as between SWS and muscle fiber size. Together, these data demonstrate the ability of US-SWEI to evaluate dystrophic diaphragm functionality over time and predict the biochemical and morphological make-up of the diaphragm. Additionally, our results highlight the advantage of US-SWEI over ex vivo testing by obtaining longitudinal measurements in the same subject. STATEMENT OF SIGNIFICANCE: In DMD patients, muscles experience cycles of regeneration and degeneration that contribute to chronic inflammation and muscle weakness. This pathology only worsens with time and leads to muscle wasting, including in respiratory and cardiac muscles. Because respiratory failure is a major contributor to premature death in DMD patients, the diaphragm muscle is an important muscle to evaluate and treat over time. Currently, diaphragm function is assessed using ex vivo force testing, a technique that only allows measurement at sacrifice. In contrast, ultrasonography, particularly shear wave elasticity imaging (USSWEI), is a promising tool for longitudinal assessment; however, most US-SWEI in DMD patients aimed for limb muscles only with the absence of preclinical studies. This work broadens the applications of US-SWE imaging by demonstrating its ability to track properties and function of dystrophic diaphragm muscles longitudinally in multiple dystrophic mouse models.
杜氏肌营养不良症（DMD）导致患者出现行走障碍和心肺衰竭，后者导致患者过早死亡。由于膈在呼吸中起作用，因此是研究的重要肌肉。评估膈功能的常用方法是离体力测试，该方法仅允许进行终点测量。相比之下，超声剪切波弹性成像（US-SWEI）可以随时间评估膈功能；但是，迄今为止，针对 DMD 患者的 US-SWEI 研究仅集中在四肢，而没有临床前研究。在这项工作中，我们使用 US-SWEI 来估计 6 个月和 12 个月龄的健康（WT）小鼠、mdx 小鼠和 mdx 小鼠 utrophin 部分不足（mdx-utr）的膈肌中的剪切波速度（SWS）。然后，在 12 个月时对膈进行离体力测试和组织学分析。在 6 至 12 个月之间，WT 小鼠的 SWS 增加了 23.8％，mdx 小鼠的 SWS 增加了 27.8％，而 mdx-utr 小鼠的 SWS 没有显着差异。mdx-utr 膈在抽搐刺激后产生的比 WT 膈产生的特定力低。观察到 SWS 与胶原沉积之间以及 SWS 与肌纤维大小之间存在很强的相关性。这些数据共同证明了 US-SWEI 能够随时间评估 DMD 膈的功能，并预测膈的生化和形态组成。此外，我们的结果通过在同一对象中获得纵向测量值，突出了 US-SWEI 相对于离体测试的优势。 意义声明：在 DMD 患者中，肌肉经历再生和退化的循环，这导致慢性炎症和肌肉无力。随着时间的流逝，这种病理学只会恶化，并导致肌肉消耗，包括呼吸肌和心肌。由于呼吸衰竭是 DMD 患者过早死亡的主要原因，因此膈肌是随时间评估和治疗的重要肌肉。目前，通过离体力测试评估膈功能，该技术仅允许在牺牲时进行测量。相比之下，超声，尤其是剪切波弹性成像（USSWEI），是一种很有前途的纵向评估工具；但是，大多数针对 DMD 患者的 US-SWEI 仅针对肢体肌肉，而没有临床前研究。这项工作通过证明其在多个 DMD 小鼠模型中能够随时间跟踪 DMD 膈肌的特性和功能，拓宽了 US-SWE 成像的应用范围。
