Skeletal Innervation in Fetal Alcohol Syndrome

About This Grant

Project Summary/Abstract Fetal alcohol spectrum disorders are a group of physical and mental defects caused by fetal exposure to alcohol, including the most severe form known as fetal alcohol syndrome (FAS). A diagnosis of FAS requires severe growth deficiency, but little is known about the mechanism by which exposure to alcohol affects the fetal skeleton. Our previous work demonstrated that normal skeletal development in mice requires peripheral innervation by sensory nerves through NGF-TrkA signaling. Furthermore, inhibition of NGF-TrkA signaling during development results in skeletal deficits in mice that mirror those observed in rodents exposed to alcohol during development as well as in children with FAS. Thus, the main objective of this study is to determine how prenatal alcohol exposure in mice affects the innervation of bone during endochondral ossification. Our overall hypothesis is that disruption of the neurotrophic NGF-TrkA signaling axis due to alcohol exposure negatively affects the innervation of fetal bone, which negatively impacts bone mass and length. This hypothesis will be directly tested in two specific aims. First, we will characterize skeletal innervation in mice exposed to alcohol during development. Here, alcohol will be administered to three strains of pregnant reporter mice by alcohol vapor exposure. Histological examination of these mice will be performed throughout skeletal development to quantify NGF expression, osteoprogenitor pool population, innervation, and vascularization. In addition, dorsal root ganglia will be harvested to quantify neuronal number and type. Next, we will determine if increasing NGF-TrkA signaling is sufficient to mitigate alcohol-induced skeletal deficits. Here, pregnant mice will be exposed to alcohol vapor starting 9 days after vaginal plug. Either NGF, gambogic amide, or vehicle (control) will be administered every third day after embryonic day 9 until birth. Bones will be harvested at postnatal day 7, 21, and 56 for analysis by microCT, static and dynamic histomorphometry, histology, and immunohistochemistry. Lumbar spine will be harvested to analyze the size, number, and type of DRG neurons. This study will explore a completely novel paradigm regarding the pathobiology of the skeletal abnormalities observed in children with fetal alcohol spectrum disorders. Importantly, the results will make a significant contribution towards understanding the effects of alcohol on fetal bone and may provide a curative strategy to address one of the major complications associated with FAS.