Active - Currently funded and in progress
This study will investigate the hypothesis that hindlimb suspension induces structural and functional changes in choroid plexus (where CSF is produced) and arachnoid granulations (where CSF is absorbed), including evidence of inflammation or fibrosis, changes in aquaporin level and changes in cell-cell adhesion protein expression. Such changes are hypothesized to occur concomitant with fluid shift caused by the positional change, which may affect the production and paracellular/ transcellular CSF outflow and thus, CSF homeostasis. Supraphysiologic pressures in the in vitro model also simulates this fluid shift and allows for direct measurement of changes in paracellular/transcellular CSF outflow through the arachnoid cell layer. This task will evaluate and investigate these measures in a cohort of hindlimb suspended rats. Task completion will contribute to closing the knowledge gap surrounding the etiology of the VIIP syndrome by characterizing and quantifying the observed physiological changes.
In consideration of the experimental design of the parent animal experiment and its organization in cohorts, this study proposes the following specific aims:
1. To perform genome-wide expression analysis in the CP and AV of rats subjected to HS and their normal posture controls, including analysis of the expression of aquaporins (water-selective channels) at various time points within each of the two cohorts available for tissue sharing.
2. To study and compare the ultrastructure of the CP and AG and the localization and distribution of aquaporins and of cellular junction proteins (tight junctions, desmosomes, adherens junctions) of the endothelial cell layer of the venous sinuses, in normal posture and in HR rats within each cohort.
*Note: Due to the fact that it is unlikely that frozen brain will be made available from cohort 1 (young male rats), we will not be able to investigate gender or age differences in the response to
HS. Only longitudinal comparisons will be possible within each cohort. Depending on the sequence of cohorts implemented in the parental animal study, we will be provided with tissue from old male rats or young female rats (cohort 3) and any one of young males, young females, or aged males, exposed to enriched CO2 (cohort 4).