Schmidt Cameron A, Ryan Terence E, Lin Chien-Te, Inigo Melissa M R, Green Tom D, Brault Jeffrey J, Spangenburg Espen E, McClung Joseph M
Department of Physiology, East Carolina University, Greenville, NC; Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC.
Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC; Department of Kinesiology, East Carolina University, Greenville, NC.
J Vasc Surg. 2017 May;65(5):1504-1514.e11. doi: 10.1016/j.jvs.2016.04.041. Epub 2016 Dec 23.
Reduced skeletal muscle mitochondrial function might be a contributing mechanism to the myopathy and activity based limitations that typically plague patients with peripheral arterial disease (PAD). We hypothesized that mitochondrial dysfunction, myofiber atrophy, and muscle contractile deficits are inherently determined by the genetic background of regenerating ischemic mouse skeletal muscle, similar to how patient genetics affect the distribution of disease severity with clinical PAD.
Genetically ischemia protected (C57BL/6) and susceptible (BALB/c) mice underwent either unilateral subacute hind limb ischemia (SLI) or myotoxic injury (cardiotoxin) for 28 days. Limbs were monitored for blood flow and tissue oxygen saturation and tissue was collected for the assessment of histology, muscle contractile force, gene expression, mitochondrial content, and respiratory function.
Despite similar tissue O saturation and mitochondrial content between strains, BALB/c mice suffered persistent ischemic myofiber atrophy (55.3% of C57BL/6) and muscle contractile deficits (approximately 25% of C57BL/6 across multiple stimulation frequencies). SLI also reduced BALB/c mitochondrial respiratory capacity, assessed in either isolated mitochondria (58.3% of C57BL/6 at SLI on day (d)7, 59.1% of C57BL/6 at SLI d28 across multiple conditions) or permeabilized myofibers (38.9% of C57BL/6 at SLI d7; 76.2% of C57BL/6 at SLI d28 across multiple conditions). SLI also resulted in decreased calcium retention capacity (56.0% of C57BL/6) in BALB/c mitochondria. Nonischemic cardiotoxin injury revealed similar recovery of myofiber area, contractile force, mitochondrial respiratory capacity, and calcium retention between strains.
Ischemia-susceptible BALB/c mice suffered persistent muscle atrophy, impaired muscle function, and mitochondrial respiratory deficits during SLI. Interestingly, parental strain susceptibility to myopathy appears specific to regenerative insults including an ischemic component. Our findings indicate that the functional deficits that plague PAD patients could include mitochondrial respiratory deficits genetically inherent to the regenerating muscle myofibers.
骨骼肌线粒体功能降低可能是导致外周动脉疾病（PAD）患者常出现的肌病和基于活动的功能受限的一个促成机制。我们推测，线粒体功能障碍、肌纤维萎缩和肌肉收缩功能缺陷本质上由再生性缺血小鼠骨骼肌的遗传背景决定，这类似于患者遗传学如何影响临床PAD疾病严重程度的分布。
对具有遗传缺血保护作用的（C57BL/6）小鼠和易感性（BALB/c）小鼠进行单侧亚急性后肢缺血（SLI）或肌毒性损伤（心脏毒素），持续28天。监测后肢血流量和组织氧饱和度，并收集组织用于组织学、肌肉收缩力、基因表达、线粒体含量和呼吸功能的评估。
尽管两品系之间组织氧饱和度和线粒体含量相似，但BALB/c小鼠出现持续性缺血性肌纤维萎缩（为C57BL/6小鼠的55.3%）和肌肉收缩功能缺陷（在多个刺激频率下约为C57BL/6小鼠的25%）。SLI还降低了BALB/c小鼠的线粒体呼吸能力，在分离的线粒体中评估（SLI第7天为C57BL/6小鼠的58.3%，SLI第28天在多种条件下为C57BL/6小鼠的59.1%），或在透化的肌纤维中评估（SLI第7天为C57BL/6小鼠的38.9%；SLI第28天在多种条件下为C57BL/6小鼠的76.2%）。SLI还导致BALB/c小鼠线粒体钙保留能力降低（为C57BL/6小鼠的56.0%）。非缺血性心脏毒素损伤显示两品系之间肌纤维面积、收缩力、线粒体呼吸能力和钙保留的恢复情况相似。
在SLI期间，缺血易感的BALB/c小鼠出现持续性肌肉萎缩、肌肉功能受损和线粒体呼吸缺陷。有趣的是，亲本品系对肌病的易感性似乎特定于包括缺血成分在内的再生性损伤。我们的研究结果表明，困扰PAD患者的功能缺陷可能包括再生性肌肉肌纤维遗传固有的线粒体呼吸缺陷。
