The modified weight-drop technique is an easy, cost-effective procedure used for the induction of mild traumatic brain injury in juvenile rats. This novel technique produces clinically relevant symptomology that will advance the study of mild traumatic brain injury (mTBI) and concussion.
Despite growing evidence that childhood represents a major risk period for mild traumatic brain injury (mTBI) from sports-related concussions, motor vehicle accidents, and falls, a reliable animal model of mTBI had previously not been developed for this important aspect of development. The modified weight-drop technique employs a glancing impact to the head of a freely moving rodent transmitting acceleration, deceleration, and rotational forces upon the brain. When applied to juvenile rats, this modified weight-drop technique induced clinically relevant behavioural outcomes that were representative of post-concussion symptomology. The technique is a rapidly applied procedure with an extremely low mortality rate, rendering it ideal for high-throughput studies of therapeutics. In addition, because the procedure involves a mild injury to a closed head, it can easily be used for studies of repetitive brain injury. Owing to the simplistic nature of this technique, and the clinically relevant biomechanics of the injury pathophysiology, the modified weight-drop technique provides researchers with a reliable model of mTBI that can be used in a wide variety of behavioural, molecular, and genetic studies.
虽然有许多广泛使用的方法的中度至重度创伤性脑损伤(TBI),极少数技术已被开发以诱导温和的生成,关闭头部受伤在啮齿类动物。由于这样的事实,轻度创伤性脑损伤(MTBI)比中度和重度脑损伤合并1三次多见,MTBI的可靠模型,需要以促进关于研究生理学,神经生物学和行为结果,和治疗策略。例如,部分由于当前的动物模型2的局限性,在过去十年中已经有超过200个失败的临床药物试验用于TBI 3的治疗。当转化研究研究,产生模拟系统,对调查结果的适用性取决于实施该模型的有效性。对于MTBI /脑震荡的研究中,一个可靠的动物模型不仅模仿生物力学力量responsible对于损伤的病因,而且还会引起与报告的临床相关人口一致的症状。此外,由于儿童处于特别高风险MTBI,优化建模系统将适用于广大青少年啮齿动物,除了成年当量。
,其中运动员有持续mTBIs震荡或脑损伤的情况下,生物力学分析表明,最关键的预测因子的伤害是快速的头加速和高速冲击4。大部分目前用于TBI诱导啮齿类动物模型的允许头5(综述参见2)很少或没有移动。这里列出的模式,提供了高速冲击物理潇洒的少年大鼠是伴随着一个180°旋转和自由落体适用加速/减速力被摄对象的头部和身体的头。牛逼这里有与MTBI的诱导本变形重量滴技术相关联的两个主要优点。首先,模型产生临床相关的震荡一样症候,而不会造成任何明显的损害到大脑(完整描述行为结果见6)。与后震荡综合征的临床报告也一致,此修改重锤落下技术生产异构的结果。虽然从MTBI的效果是显著,存在经历了MTBI上的多个结果的措施检查当啮齿动物之间大幅变化。其次,该方法允许重复MTBI 7的研究。由于大多数现有的TBI模型造成如此严重的伤害,这是常常难以诱导的第二损伤,并且几乎不可能研究重复TBI而不对整个皮质广泛损害。
因此,对于使用改性重量滴法对工业家里的主要理由MTBI的ction是产生伤害更紧密地代表了青少年群体的病理生理和脑震荡的症状学和重复TBI。随着MTBI的发病率越来越高,涉及到体育,坠落,交通事故,特别是在儿童时期,MTBI这种独特的啮齿动物模型为研究人员提供了震荡式的脑损伤,可以很容易地应用到多个命中研究的宝贵工具范式。
Reliable modelling systems are needed to effectively cultivate basic science research that has significant translational validity. In response to rising occurrences and popular media, the investigation of mTBI and concussion has become a priority in many disciplines. However, despite increased research, there have been only incremental improvements in therapeutic strategies and treatment options 3. This lack of progress may be partially due to a discrepancy between the modeling systems employed and actual injury etiology. The majority of studies utilized rodent models that failed to reproduce the important biomechanical forces and appropriate post-injury symptomology. The current human definition of mTBI specifies that the injury results from acceleration and deceleration forces associated with a blunt trauma 10. The modified weight drop technique described here is therefore an ideal model for the study of mTBI and concussion because it uses a glancing impact to cause rapid rotational acceleration and deceleration to the head of an unrestrained animal, mimicking the biomechanical forces identified in sports-related injuries and automobile accidents. In addition, this model is easily adapted to examine repetitive mTBI, a phenomena that is emerging as a serious medical and socioeconomic issue. Studies indicate that rodents may be exposed to a series of 10 distinct mTBIs with minimal mortality 7. Finally, the method is inexpensive and can be carried out rapidly, allowing for high-throughput examination of a many therapeutic compounds and treatment regiments.
Just as with any procedural technique, certain aspects of the protocol are particularly important to the generation of reliable results. First, the tin foil needs to be scored effectively. If the tin foil is not properly scored, the force imparted by the weight during the glancing impact will not be enough to propel the juvenile rat through the tin foil onto the collection sponge. In these situations, the rat will remain in the starting position (chest down on the tin foil) and the mTBI will result from the blunt trauma from the weight impacting the stationary head, not the rotational acceleration and deceleration desired. Second, during the induction of the mTBI and the sham injury, the level of anesthetic applied to each rat should be consistent. Owing to the fact that time-to-right is used as marker of mTBI, the researcher should try to ensure that animals receiving a mTBI and animals receiving a sham injury are exposed to similar levels of anesthetic. A major advantage to this technique over many other TBI procedures is the low level and duration of anesthesiology. However, the juvenile rat needs to be non-responsive to a toe or tail pinch to ensure they do not wake-up on the stage before the injury is induced. Finally, in order to maintain a consistent injury etiology, the positioning of the rat’s head is particularly important. Ideally the weight should impact the center of the dorsal surface of the head. Caution should be taken to avoid positioning the path of the weight too near the caudal/posterior portion of the head, as impacting the brainstem and cerebellum is associated with increased mortality and seizure activity.
Based upon the biomechanical pathophysiology of injury induction and the behavioural outcomes examined, the modified weight-drop technique appears to be a reliable model for the investigation of paediatric mTBI and concussion. Although preliminary studies of this novel model have assessed some basic molecular and structural changes 7 future studies will be needed to ascertain how the brain responds to a mTBI with this injury etiology. An in-depth analysis of the neuroanatomical and biological changes that occur at the cellular and epigenetic level would increase model validity and translational applicability. In addition to stimulating the generation of targeted pharmacological therapies, understanding the pathophysiological changes that occur in the brain in response to mTBI and concussion would also direct the research related to clinical biomarkers that have the ability to predict outcomes following injury.
The authors have nothing to disclose.
The authors would like to thank Irene Ma, Rose Tobais, and Jong Rho for their technical assistance. Funding was provided to MJE by the Department of Pediatrics at the University of Calgary, the Alberta Children’s Hospital Foundation (ACHF) and the Alberta Children’s Hospital Research Institute (ACHRI). The Postdoctoral fellowship for RM was provided by ACHF.
Brass Weights | Ginsberg Scientific | 7-2500-2 | Need to have metal loop attached to base |
Alluminum Foil | Alcan | Available at most grocery stores | |
Masking Tape | Commercially available | ||
U-Shaped Plastic Stand | Constructed by Laboratory | ||
Clamp Stand | Sigma-Aldrich | Z190357 | |
Plastic Guide Tube | Could be constructed or purchased at a hardware store | ||
Fishing Line | Angler 10lb | Purchased from a sporting goods retailer | |
Isoflurane | Pharmaceutical Partners of Canada | DIN 02237518 | Inhalation Anesthetic |
Topical Lidocaine (30ml) | Astra Zeneca | DIN 0001694 | Xylocaine Jelly 2% |
Cotton Swabs | Commercially available | ||
Heating Pad – 3 heat setting | Commercially available | ||
Stop Watch | Sportline | L303 | Purchased from a sporting goods retailer |
Video Camera | Sony | HDR-CX260V | |
Sprague Dawley Rats | Charles River Laboratories | SAS SD 40 | Male and females ordered from Charles River Laboratories and pups bred in-house |
Balance Beam | Constructed by Laboratory |