Locomotor Training with Anabolic Adjuvants for Musculoskeletal Recovery After SCI

肌肉和骨丢失是脊髓损伤（SCI）的标志性后果，阻碍了身体康复 并使健康状况恶化。这种肌肉骨骼的衰退是由于 神经损伤，并由其他因素加剧，包括受损的胰岛素样生长因子（IGF）-1 肌肉和骨骼中的信号。多因素损伤的存在可能是相对 大多数独立的药理学和机械重新加载策略在再生两者中的无效性 严重SCI后的骨骼和肌肉。我们的目标是建立一个多模式的战略结合物理 康复与辅助IGF-1，以促进SCI后肌肉骨骼恢复，从而解决这两个问题， 废用和受损的合成代谢信号。我们的数据表明，被动循环训练和体重 支持跑步机（TM）训练，以活动为基础的身体康复形式，减少肌肉损失， 促进啮齿动物中度挫伤SCI后的神经可塑性。然而，这些身体康复 治疗方案在严重SCI后再生肌肉和骨骼方面相对无效。已知IGF-1 独立地影响肌肉骨骼的完整性，这表明这种合成代谢可能是一个可行的候选人， 改善SCI后的身体康复。事实上，我们的数据表明，肌肉中IGF-1的病毒过表达 在废用过程中保护肌肉，并在重新加载时促进肌肉和骨骼的恢复。此外，病毒IGF- 1的表达已被证明可促进脊髓横断后皮质脊髓运动神经元的存活， 对脊髓损伤后肌肉功能的保护至关重要。然而，病毒IGF-1疗法并不高 翻译为了解决这个问题，我们开发了一种新的口服生物可利用的人IGF-1表达在可食用的 植物（Plant-Pro-IGF-1），并优化了大鼠和小鼠的给药方案， 300-500%至少12小时，不抑制循环葡萄糖。我们还证明了植物- Pro-IGF-1到达骨骼肌，主要靶组织，并且Plant-Pro-IGF-1磷酸化IGFR 和Akt在培养的细胞中以时间和剂量依赖的方式表达，验证生物活性。对于这一建议，我们将 在我们的啮齿动物中评估Plant-Pro-IGF-1单独和与基于活动的身体康复组合 严重挫伤SCI模型，这代表了将这种高度新颖的化合物转化为 SCI患者的临床试验。所有研究将在4个月大的雄性和雌性Sprague中进行。 接受假手术的道利大鼠与严重胸中部（T9）挫伤SCI。我们将进行实验 使用立即和延迟治疗策略来确定预防和再生功效， 这提供了对最合适的治疗窗口的洞察。我们亦会评估 被动（循环）与动态（TM）负荷对IGF-1功效影响，我们将评估前肢和 后肢肌肉骨骼结局，以确定治疗有效性是否需要正常的神经支配或 未受损的运动活动，严重T9 SCI后仅存在于前肢的因素。成果包括： 肌肉横截面积（通过MRI）、肌肉形态学（通过免疫组织化学）、离体肌肉 力学、肌肉IGF-1信号传导、骨体积（通过microCT）、骨转换（通过组织形态计量学和 循环标志物）、比目鱼肌皮质脊髓运动神经元形态/分布和血清IGF-1、IGF结合 蛋白质3和葡萄糖。该提案有两个具体目标： 目标1。评价给予IGF-1增强急性肌肉骨骼效应的能力， 在啮齿动物挫伤SCI模型中进行基于活动的身体康复。 目标二。确定多模式治疗结合基于活动的物理康复与 当在严重SCI后长期施用时，辅助IGF-1再生骨骼和肌肉。

Muscle and bone loss are hallmark consequences of spinal cord injury (SCI) that impede physical rehabilitation and worsen health outcomes. This musculoskeletal decline is precipitated by disuse resulting from the neurologic insult and is intensified by other factors, including impaired insulin-like growth factor (IGF)-1 signaling in muscle and bone. The presence of multifactorial impairments likely underlies the relative ineffectiveness of most stand-alone pharmacologic and mechanical reloading strategies in regenerating both bone and muscle after severe SCI. Our goal is to establish a multimodal strategy combining physical rehabilitation with adjuvant IGF-1 to promote musculoskeletal recovery after SCI, thus addressing both the disuse and the impaired anabolic signaling. Our data indicate that passive Cycle training and bodyweight supported treadmill (TM) training, forms of activity-based physical rehabilitation, reduce muscle loss and promote neuroplasticity in rodents after moderate contusion SCI. However, these physical rehabilitation regimens are relatively ineffective in regenerating muscle and bone after severe SCI. IGF-1 is known to independently influence musculoskeletal integrity, suggesting this anabolic may represent a viable candidate to improve physical rehabilitation after SCI. Indeed, our data indicate that viral overexpression of IGF-1 in muscle protects muscle during disuse and promotes muscle and bone recovery upon reloading. Additionally, viral IGF- 1 expression has been shown to promote corticospinal motor neuron survival after spinal cord transection, an effect essential to the preservation of muscle function after SCI. However, viral IGF-1 therapies are not highly translational. To address this, we developed a novel orally-bioavailable human IGF-1 expressed in edible plants (Plant-Pro-IGF-1) and optimized a dosing regimen in rats and mice that increases circulating IGF-1 by 300-500% for at least 12 h, without suppressing circulating glucose. We have also demonstrated that Plant- Pro-IGF-1 reaches skeletal muscle, the primary target tissue, and that Plant-Pro-IGF-1 phosphorylates IGFR and Akt in time and dose-dependent manners in cultured cells, validating bioactivity. For this proposal, we will evaluate Plant-Pro-IGF-1 alone and in combination with activity-based physical rehabilitation in our rodent severe contusion SCI model, which represents the next step in translating this highly novel compound to clinical trials in the SCI population. All studies will be conducted in 4-month old male and female Sprague- Dawley rats receiving Sham surgery vs severe mid-thoracic (T9) contusion SCI. We will perform experiments using immediate and delayed treatment strategies to determine preventative and regenerative efficacy, respectively, which provides insight into the most appropriate treatment window. We will also assess the influence of passive (Cycle) vs dynamic (TM) loading on IGF-1 efficacy and we will evaluate forelimb and hindlimb musculoskeletal outcomes to determine if therapeutic efficacy requires normal innervation or unimpaired locomotor activity, factors that are only present in forelimbs after severe T9 SCI. Outcomes include: muscle cross sectional area (via MRI), muscle morphology (via immunohistochemistry), isolated muscle mechanics, muscle IGF-1 signaling, bone volume (via microCT), bone turnover (via histomorphometry and circulating markers), soleus corticospinal motor neuron morphology/distribution, and serum IGF-1, IGF binding protein 3, and glucose. This proposal has two Specific Aims: Aim 1. Evaluate the ability of administered IGF-1 to enhance the acute musculoskeletal effects of activity-based physical rehabilitation in a rodent contusion SCI model. Aim 2. Determine if a multimodal therapy combining activity-based physical rehabilitation with adjuvant IGF-1 regenerates bone and muscle when administered chronically after severe SCI.