Laboratory for Neuropathology, Department of Neurology, Ghent University, 9000 Ghent, Belgium.
Ghent-Fertility and Stem cell Team (G-FaST), Department of Human Structure and Repair, Ghent University, 9000 Ghent, Belgium.
Front Biosci (Schol Ed). 2022 Jul 15;14(3):19. doi: 10.31083/j.fbs1403019.
Stress-inducible heat shock protein 70 (HSP70) is both a protective chaperone involved in protein homeostasis and an immune regulator. In both capacities, HSP70 has been implicated in muscle disorders, yet with fragmented and differing results. In this study we aimed to compare results obtained in the mouse model for the severest form of muscular dystrophy (MD) equivalent to Duchenne MD, termed the mdx mouse, with results obtained in human MD.
Skeletal muscle and serum samples were obtained from 11 healthy controls, 11 fully characterized patients diagnosed with Becker MD and limb girdle MD (LGMD), and six muscle disease controls. In addition, muscle extracts were prepared from tibialis anterior of mdx and control mice at ages 4, 8 and 12 weeks. The HSP70 levels were quantified using RT-PCR, western blotting and protein arrays, and localized in muscle tissue sections using double immunofluorescence.
We found selective and significant 2.2-fold upregulation of HSP70 protein in mdx tibialis muscle at the earliest disease phase only. In LGMD and Becker MD patients, HSP70 protein levels were not significantly different from those of healthy muscle and serum. HSP70 was localized to regenerating muscle fibers both in mouse and human MD skeletal muscle tissues. Toll-like receptor (TLR) 2 and TLR4 expression was moderately increased on the sarcolemma in MD muscle, yet protein levels were not significantly different from normal controls.
HSP70 upregulation in MD appears disease stage-dependent, marking the phase of most active muscle regeneration in the mdx mouse. We postulate that well-timed supportive therapeutic interventions with HSP70 agonists could potentially improve muscle tissue's regenerative capacities in MD, attenuating loss of muscle mass while we await gene therapies to become more widely available.
应激诱导热休克蛋白 70（HSP70）既是参与蛋白质动态平衡的保护性伴侣分子，也是一种免疫调节剂。在这两种功能中，HSP70 都与肌肉疾病有关，但结果却各不相同。在这项研究中，我们旨在比较最严重形式的肌肉营养不良（MD）的小鼠模型（与杜氏 MD 相当的 mdx 小鼠）和人类 MD 中获得的结果。
从 11 名健康对照者、11 名经充分特征鉴定的诊断为 Becker MD 和肢带 MD（LGMD）的患者以及 6 名肌肉疾病对照者中获得骨骼肌和血清样本。此外，还从 4、8 和 12 周龄的 mdx 和对照小鼠的比目鱼肌中制备肌肉提取物。使用 RT-PCR、western blot 和蛋白质芯片定量 HSP70 水平，并使用双免疫荧光在肌肉组织切片中定位 HSP70。
我们发现，仅在最早的疾病阶段，mdx 比目鱼肌中的 HSP70 蛋白选择性和显著上调了 2.2 倍。在 LGMD 和 Becker MD 患者中，HSP70 蛋白水平与健康肌肉和血清无显著差异。在人类和小鼠 MD 骨骼肌组织中，HSP70 定位于再生的肌纤维。MD 肌肉的肌膜上 TLR2 和 TLR4 的表达适度增加，但蛋白水平与正常对照无显著差异。
MD 中的 HSP70 上调似乎与疾病阶段有关，标志着 mdx 小鼠中最活跃的肌肉再生阶段。我们推测，在等待基因治疗更广泛应用的同时，适时进行 HSP70 激动剂的支持性治疗干预，可能会改善 MD 肌肉组织的再生能力，减轻肌肉质量的损失。
