Department of Clinical Sciences Lund, Division of Pediatrics, Lund University, Skåne University Hospital, 21185, Lund, Sweden.
School of Health and Biomedical Sciences, STEM College, RMIT University, Bundoora, 3083, VIC, Australia.
Pediatr Res. 2022 Aug;92(2):403-414. doi: 10.1038/s41390-022-02075-y. Epub 2022 May 3.
Intraventricular hemorrhage causes significant lifelong mortality and morbidity, especially in preterm born infants. Progress in finding an effective therapy is stymied by a lack of preterm animal models with long-term follow-up. This study addresses this unmet need, using an established model of preterm rabbit IVH and analyzing outcomes out to 1 month of age.
Rabbit pups were delivered preterm and administered intraperitoneal injection of glycerol at 3 h of life and approximately 58% developed IVH. Neurobehavioral assessment was performed at 1 month of age followed by immunohistochemical labeling of epitopes for neurons, synapses, myelination, and interneurons, analyzed by means of digital quantitation and assessed via two-way ANOVA or Student's t test.
IVH pups had globally reduced myelin content, an aberrant cortical myelination microstructure, and thinner upper cortical layers (I-III). We also observed a lower number of parvalbumin (PV)-positive interneurons in deeper cortical layers (IV-VI) in IVH animals and reduced numbers of neurons, synapses, and microglia. However, there were no discernable changes in behaviors.
We have established in this preterm pup model that long-term changes after IVH include significant wide-ranging alterations to cortical organization and microstructure. Further work to improve the sensitivity of neurocognitive testing in this species at this age may be required.
This study uses an established animal model of preterm birth, in which the rabbit pups are truly born preterm, with reduced organ maturation and deprivation of maternally supplied trophic factors. This is the first study in preterm rabbits that explores the impacts of severe intraventricular hemorrhage beyond 14 days, out to 1 month of age. Our finding of persisting but subtle global changes including brain white and gray matter will have impact on our understanding of the best path for therapy design and interventions.
脑室内出血会导致早产儿，尤其是早产儿，出现严重的终生死亡率和发病率。由于缺乏具有长期随访的早产儿动物模型，因此在寻找有效治疗方法方面进展受阻。本研究通过使用已建立的早产儿兔脑室内出血模型，并分析至 1 个月龄的结果，解决了这一未满足的需求。
将兔幼仔早产并在生命的 3 小时内给予腹腔内注射甘油，大约 58%的幼仔发生脑室内出血。在 1 个月龄时进行神经行为评估，然后对神经元、突触、髓鞘形成和中间神经元的表位进行免疫组织化学标记，通过数字定量进行分析，并通过双向 ANOVA 或学生 t 检验进行评估。
脑室内出血的幼仔大脑的髓鞘含量普遍降低，皮质髓鞘形成的微观结构异常，皮质上层（I-III 层）变薄。我们还观察到，脑室内出血动物的深层皮质（IV-VI 层）中的 PV 阳性中间神经元数量减少，神经元、突触和小胶质细胞数量减少。然而，行为上没有明显的变化。
我们在该早产幼仔模型中确立了一个长期的观点，即在脑室内出血后，包括皮质组织和微观结构在内的广泛变化。为了提高该年龄段该物种神经认知测试的灵敏度，可能需要进一步的工作。
本研究使用了一种已建立的早产动物模型，在该模型中，兔幼仔真正早产，器官成熟度降低，并且缺乏母体提供的营养因子。这是首次在早产兔中研究严重脑室内出血的影响，时间超过 14 天，至 1 个月龄。我们发现持续存在但细微的全局变化，包括脑白质和灰质，这将对我们理解治疗设计和干预的最佳途径产生影响。
