Validation of pre-clinical models of musculoskeletal healing following trauma

随着年龄的增长，日常生活能力(ADL)急剧下降，功能和修复能力下降 肌肉骨骼(MSK)组织是造成这种损失的一个重要因素。退伍军人特别容易受到 ADL的减少，因为经历严重创伤伤害多个MSK组织的可能性是 服兵役的人比平民百姓要高。虽然这些严重的创伤现在对生命的威胁较小 与过去相比，MSK再生的并发症出现，并导致以后需要辅助生活 生活。因此，迫切需要临床前的多发伤损伤模型，以促进对 将糟糕的MSK修复与较少的ADL联系起来的机制。文献中有几个这样的模型，但都没有 已经针对与MSK再生受损相关的关键临床问题进行了验证， 即骨折延迟愈合，肌肉纤维化或软组织钙化，骨质疏松症，认知障碍， 对疼痛敏感，以及高度炎症。因此，该项目的目标是验证小鼠的模型 复合损伤-皮肤烧伤，后肢肌肉损伤，股骨中段骨折- 能够概括导致ADL减少的许多问题。在目标1中，我们将比较康复反应 3个损伤组中的成年转基因小鼠：i)单侧股骨骨折或下部单侧肌肉损伤 后肢，II)股骨骨折合并单肌肉损伤，III)合并股骨骨折、肌肉损伤和皮肤 烧了吧。当NFκB调节元件激活时，这些转基因小鼠表达荧光素酶，从而允许 美国通过生物发光成像组织炎症。为了验证模型，我们将确定骨折愈合是否 在多发性创伤小鼠中，在伤后28天(DPI)延迟，而在42天DPI时肌肉纤维化持续存在 对单次损伤的小鼠。在目标2中，使用目标1中相同的小鼠，但添加假窝产仔(无损伤)，我们将 比较5组损伤对退行性变的影响：1)假手术对照组，2)单侧股骨骨折，3)单侧股骨骨折 后肢肌肉损伤；4)骨骼和肌肉双重损伤；5)多发伤合并 皮肤灼伤。从基线(受伤前)和受伤后间隔开始，面骨密度(双能量) X-射线骨密度仪)未损伤的股骨、全身重量(质量)、认知功能(新对象 识别测试)、疼痛敏感性(对机械刺激的痛觉过敏和痛觉过敏)、睡眠时间(CAGE 活动)和机动性(自愿车轮跑步和步态分析)将在42DPI之前进行评估。此外， 对侧未损伤的股骨和腰椎体将通过μCT进行体外成像，并接受 三点弯曲(股骨)或压缩(椎骨)的载荷-失效试验，以确定皮质骨 结构、骨小梁微结构、体积骨密度和强度在不同的 组。从退变、骨丢失和骨强度方面验证复合多发伤模型 复合伤组比非损伤组和假手术组分别需要高和低。在……里面 此外，我们的另一个验证目标是证明MSK对骨骼和肌肉与皮肤的联合损伤 烧伤还会损害记忆力，导致对疼痛过敏，缩短睡眠时间，减少运动 因为这些都是多发伤的临床并发症。在目标3中，血液样本将在安乐死时从 AIM 1中的小鼠(28-DPI和42-DPI)以及来自更早时间点的额外的NFκB报告小鼠(1- DPI、3-DPI、7-DPI和14-DPI)，以便我们可以量化高炎症反应的时间变化 致伤。在安乐死之前，我们会对所有的小鼠进行体内成像，以评估组织炎症，在安乐死之后， 我们将在体外对单个器官进行成像。为了验证模型，全身炎症和组织 多发伤合并伤组较单发伤组炎症持续时间更长。 用一种经过验证的多发伤小鼠模型，该模型具有与贫穷相关的许多临床问题 肌肉骨骼组织的再生，未来的研究可以确定和研究机制，治疗 战略和预言家，将帮助退伍军人保持日常生活活动，随着他们的年龄。

With aging, there is a precipitous loss in activities of daily living (ADLs), and a decline in the function and repair of musculoskeletal (MSK) tissues is a significant contributor to this loss. Veterans are particularly vulnerable to a reduction in ADLs because the likelihood of experiencing severe trauma that injuries multiple MSK tissues is higher in military service than in civilian life. While these severe traumatic injuries are less life-threatening now than in the past, complications of MSK regeneration arise and lead to the requirement of assisted living later in life. Thus, there is a strong need for preclinical models of polytrauma injury that facilitate studies into the mechanisms connecting poor MSK repair to fewer ADLs. Several such models exist in the literature, but none have been validated with respect to the key clinical problems associated with impaired MSK regeneration, namely delayed fracture healing, muscle fibrosis or soft tissue calcification, osteoporosis, cognitive impairment, pain sensitivity, and hyper-inflammation. Therefore, the goal of this project is to validate a murine model of combined injuries – skin burn, muscle injury to the lower hindlimb, and fracture of the femur mid-shaft – for its ability to recapitulate many of the problems that reduce ADLs. In Aim 1, we will compare the healing response of adult, transgenic mice among 3 injury groups: i) single femur fracture or single muscle injury in the lower hindlimb, ii) femur fracture plus single muscle injury, and iii) combined femur fracture, muscle injury, and skin burn. These transgenic mice express luciferase when the NFκB regulatory element is active, thereby allowing us to image tissue inflammation by bioluminescence. To validate the model, we will determine if fracture healing is delayed at 28-days post injury (DPI) and muscle fibrosis persists at 42-DPI in the polytrauma mice compared to the single injury mice. In Aim 2, using the same mice in Aim 1 but adding sham littermates (no injury), we will compare the effect of injury on degeneration among 5 groups: i) sham control, ii) single femur fracture, iii) single muscle injury in the lower hindlimb, iv) dual injury to bone and muscle, and v) combined polytrauma injury with skin burn. Starting at baseline (before injury) and at post-injury intervals, areal bone mineral density (dual-energy X-ray absorptiometry) of the uninjured femur, whole-body weight (mass), cognitive function (novel object recognition test), pain sensitivity (allodynia and hyperalgesia to mechanical stimuli), duration of sleep (cage activity), and mobility (voluntary wheel running plus gait analysis) will be assessed until 42-DPI. Additionally, the contralateral, uninjured femur and the lumbar vertebral body will be imaged ex vivo by μCT and subjected to load-to-failure tests in three-point bending (femurs) or in compression (vertebra) to determine whether the cortical structure, trabecular micro-architecture, volumetric bone mineral density, and strength are different among the groups. To validate the model of combined polytrauma with respect to degeneration, bone loss and bone strength will need to be higher and lower in the combined injury group than in the no-injury, sham group, respectively. In addition, our other validation goal is to demonstrate that the combined MSK injury to bone and muscle with skin burn also impairs memory, causes hypersensitivity to pain, reduces duration of sleep, and reduces movement as these are clinical complications of polytrauma. In Aim 3, blood samples will be collected at euthanasia from the mice in Aim 1 (28-DPI and 42-DPI) as well as from additional NFκB reporter mice at earlier time points (1- DPI, 3-DPI, 7-DPI, and 14-DPI) so that we can quantify the temporal changes in the hyper-inflammatory response to injury. Prior to euthanasia, we will image all mice in vivo to assess tissue inflammation, and after euthanasia, we will image individual organs ex vivo. To validate the model, systemic hyper-inflammation and tissue inflammation will occur for a longer period time in the polytrauma combined group than in the single injury group. With a validated murine model of polytrauma that possesses many of the clinical problems associated with poor regeneration of musculoskeletal tissue, future studies can identify and investigate mechanisms, therapeutic strategies, and prognosticators that will help Veterans maintain activities of daily living as they age.