Effects of Tamoxifen in skeletal muscle recovery after spinal cord injury and mechanisms activated by the drug

脊髓损伤(Sci)是一种无法治愈的疾病，其特征是躯体感觉丧失。 而随意运动最终会导致肌肉萎缩。大多数研究都集中在神经上。 再生而不是肌肉恢复，尽管如果肌肉退化超过了，神经再生是无用的 修理。在动物模型中，损伤后立即锻炼是减少肌肉萎缩的常见疗法，但在 人类不可能在创伤后的急性期。有效的治疗方法必须减少肌肉 在脊髓损伤后的急性期退化和改善肌肉收缩特性，直到运动成为可能。 我们实验室正在率先使用美国食品和药物管理局批准的抗癌药物三苯氧胺()来减肥 创伤后的退化。选择性雌激素受体调节剂可以逆转肌肉的变化 类型组成和减少脊髓损伤诱导的肌肉纤维收缩特性的影响，因为雌二醇， 通过雌激素受体(ER)起作用，有这些作用。此外，还有一个潜在的好处，那就是 可以刺激卫星细胞的激活/增殖。与不同ER的互动表明 对这种药物的反应可能存在性别差异。自从观察到性别差异以来， 肌肉纤维和收缩特性，有必要进行新的研究来确定对女性和 脊髓损伤后的男性肌肉组织。我们的初步数据表明，提高了运动恢复和 防止肌肉组织中的肌球蛋白丢失。因此，我们的中心假设是，早期给药 脊髓损伤后，将部分保留肌肉纤维的收缩特性，减少退变，并 最终增加肌纤维的增殖/再生。此外，我们还想探索一种可能的性行为 肌细胞对该药物的反应及激活或失活后代谢谱的差异 SCI。本项目有以下几个目标：目标1.确定预防减量的效果 对雄性和雌性大鼠脊髓损伤后骨骼肌纤维收缩特性的影响，并建立 这种药物防止肌肉退化的机制。我们将颗粒植入男性和 雌性大鼠中度挫伤后脊髓损伤。比目鱼肌和胫前肌纤维的收缩特性 将进行评估，肌球蛋白重链(MHC)亚型的表达谱将在7、14和 伤后28天(DPI)。目的2.评价对生肌因子和心肌梗死的影响。 脊髓损伤后骨骼肌中的增殖/再生蛋白及其在这些细胞中的作用 活动是根据性别而定的。雄性和雌性大鼠脊髓损伤后给予治疗。这种药物对小鼠的影响 比目鱼肌和胫骨肌成肌因子(Pax7、MyoD和Mygenin)作为卫星标志的表达 细胞激活或增殖以及与新的肌肉纤维形成相关的蛋白质(结蛋白和胚胎 MHC)将在7、14和28 DPI进行测试。这些实验和他们的结果可能导致新的治疗方法 加强脊髓损伤后肌肉和运动恢复的策略。

Spinal cord injury (SCI) is a condition without a cure, characterized by the loss of somatosensory perception and voluntary movement eventually resulting in muscle atrophy. Most research has focused on nerve regeneration not muscle recovery, although nerve regeneration is useless if muscle deterioration is beyond repair. Exercise soon after the injury is a common therapy to reduce muscle atrophy in animal models, but in humans it is not possible in the acute phase after trauma. An effective therapy must reduce muscle degeneration and improve muscle contractile properties in the acute phase after SCI until exercise is possible. Our laboratory is pioneering the use of tamoxifen (TAM), an FDA-approved cancer drug, to reduce muscle degeneration after trauma. TAM, a selective estrogen receptor modulator, could reverse the changes in muscle type composition and reduce the SCI-induced effect on muscle fiber contractile properties because estradiol, working through estrogen receptors (ER), has these effects. In addition, TAM has the potential benefit that it could stimulate Satellite cell activation/proliferation. The interaction of TAM with different ERs suggests that there is a possible sex difference in the response to this drug. Since sexual differences have been observed in muscle fibers and contractile properties, new studies are necessary to define the effect of TAM in female and male muscle tissue after SCI. Our preliminary data demonstrate that TAM improves locomotor recovery and prevents myosin loss in muscle tissue. Therefore, our central hypothesis is that TAM, administered early after SCI, will partially preserve the contractile properties of muscle fibers, reducing degeneration, and ultimately increase myofiber proliferation/regeneration. In addition, we want to explore a possible sex difference in the response to this drug and the metabolic profile activated or de-activated in muscle cells after SCI. The present project has the following aims: AIM 1. To determine the effect of TAM to prevent a reduction in the contractile properties of skeletal muscle fibers after SCI in male and female rats, and establish the mechanisms by which this drug prevents muscle degeneration. We will implant TAM pellets in male and female rats after a moderate contusion SCI. Contractile properties of Soleus and Tibialis anterior muscle fibers will be evaluated and the expression profile of myosin heavy chain (MHC) isoforms will be studied at 7, 14, and 28 days post-injury (DPI). AIM 2. To evaluate the effect of TAM on myogenic factors and proliferative/regenerative proteins from skeletal muscle after SCI and establish if the effects in these cellular events are sex-specific. Male and female rats will be treated with TAM after SCI. The effect of this drug on Soleus and Tibialis expression of myogenic factors (Pax7, MyoD and myogenin), used as markers of Satellite cell activation or proliferation and proteins associated to new muscle fiber formation (desmin and embryonic MHC) will be tested at 7, 14, and 28 DPI. These experiments and their results may lead to novel therapeutic strategies that enhance muscle and locomotor recovery after SCI.