Injury and Recovery in Developing Brain

多达50%的低出生体重婴儿由于慢性缺氧和循环系统并发症而患有认知缺陷。纵向研究表明，一些儿童在成年早期脑容量和认知功能都有所恢复，但这种恢复是可变的，这种改善的神经生物学基础尚不清楚。我们的小鼠慢性亚致死性缺氧损伤模型再现了最初的皮质体积缺陷和脑室肿大，以及随后的恢复，尽管这些小鼠中一些神经元丢失和认知异常长期存在。识别神经元恢复背后的细胞和分子事件，并找到增强这一过程的方法是这个项目的共同目标。我们假设缺氧脑损伤的恢复是由于神经源性/血管生成反应的耦合。这包括(1)神经干细胞和祖细胞的增殖，这需要神经干细胞和血管内皮中的特定生长因子；(2)新生神经元和胶质细胞群体的存活，这需要新生成细胞的能量代谢改善以及神经和血管室的营养影响。该计划的具体项目将通过生成组织特异性和时间依赖性的功能丧失或获得遗传模型来测试神经干细胞、少突胶质细胞祖细胞和血管内皮中几种增殖、存活和分化因子的功能，从而验证这些假设。研究的因子包括成纤维细胞生长因子2 （FGF2）、表皮生长因子受体（EGFR）、TrkB及其配体脑源性嗜神经生长因子（BDNF）、线粒体解偶联蛋白2 （UCP2）和肠道激素ghrelin。阐明这些基因在特定细胞类型中的作用将揭示动物在标准或强化环境中损伤恢复时血管、神经和代谢成分之间的相互作用和动态相互作用。采用多学科方法，包括形态计量学和免疫细胞化学分析、电子显微镜和电生理学，来评估所研究的信号系统是否有助于缺氧动物在富集环境下引发的适应性变化。此外，增强这些信号系统的特定成分的有益作用将在细胞和行为水平上进行测试。这些研究的长期目标是确定新的治疗干预手段，以减少早产儿的发育障碍和神经行为后遗症。

As many as 50% of low-birth-weight infants suffer cognitive deficits due to chronic hypoxia and circulatory complications. Longitudinal studies suggest recovery in both brain volume and cognitive functions by early adulthood in some children, however this recovery is variable and the neurobiological basis of this improvement are not understood. Our mouse model of chronic sublethal hypoxic injury reproduces the initial cortical volume deficit and ventriculomegaly, as well as the subsequent recovery, although some neuron loss and cognitive abnormalities persist long-term in these mice. Identifying the cellular and molecular events that underlie neuronal recovery and finding ways to enhance this process are the common goals of this program project. We hypothesize that recovery from hypoxic brain injury is due to a coupled neurogenic/angiogenic response. This includes (1) proliferation of neural stem cells and progenitors, which requires specific growth factors in neural stem cells and vascular endothelium; (2) survival of newly-born neuronal and glial populations, which requires improved energetic metabolism in the newly-generated cells and trophic influences from neural and vascular compartments. Specific projects in this program will test these hypotheses by generating tissue-specific and time-dependent loss- or gain-of function genetic models to test the function of several proliferative, survival and differentiation factors in neural stem cells, oligodendrocyte progenitors, and vascular endothelium. The factors under investigation include Fibroblast growth factor 2 (FGF2), the Epidermal growth factor receptor (EGFR), TrkB and its ligand Brain derived neurotropic growth factor (BDNF), the mitochondrial uncoupling protein 2 (UCP2) and the gut hormone ghrelin. Elucidating the role of these genes in specific cell types will reveal the reciprocal and dynamic interactions between vascular, neural and metabolic components as the animals recover from injury in standard or enriched environment. A multidisciplinary approach, which includes morphometric and immunocytochemical analyses, electron microscopy and electrophysiology, is used to assess whether the signaling systems under study contribute adaptive changes triggered by the enriched environment in hypoxic animals. Furthermore, the beneficial effect of enhancing specific components of these signaling systems will be tested at the cellular and behavioral level. The long-term goal of these studies is to identify new means of therapeutic intervention to decrease the developmental disability and neurobehavioral sequelae of preterm birth.