Characterization of MR Imaging-Visible Perivascular Spaces in the White Matter of Healthy Adolescents at 3T.

BACKGROUND AND PURPOSE: Perivascular spaces play a role in cerebral waste removal and neuroinflammation. Our aim was to provide data regarding the burden of MR imaging-visible perivascular spaces in white matter in healthy adolescents using an automated segmentation method and to establish relationships between common demographic characteristics and perivascular space burden. MATERIALS AND METHODS: One hundred eighteen 12- to 21-year-old subjects underwent T1- and T2-weighted 3T MR imaging as part of the National Consortium on Alcohol and Neurodevelopment in Adolescence. Perivascular spaces were identified in WM on T2-weighted imaging using a local heterogeneity approach coupled with morphologic constraints, and their spatial distribution and geometric characteristics were assessed. RESULTS: MR imaging-visible perivascular spaces were identified in all subjects (range, 16-287). Males had a significantly higher number of perivascular spaces than females: males, mean, 98.4 ± 50.5, versus females, 70.7 ± 36.1, (P < .01). Perivascular space burden was bilaterally symmetric (r > 0.4, P < .01), and perivascular spaces were more common in the frontal and parietal lobes than in the temporal and occipital lobes (P < .01). Age and pubertal status were not significantly associated with perivascular space burden. CONCLUSIONS: Despite a wide range of burden, perivascular spaces are present in all healthy adolescents. Perivascular space burden is higher in adolescent males than in females, regardless of age and pubertal status. In this population, perivascular spaces are highly symmetric. Although widely reported as a feature of the aging brain, awareness of the presence of perivascular spaces in a cohort of healthy adolescents provides the foundation for further research regarding the role of these structural variants in health and disease.

An injectable, biodegradable hydrogel for trophic factor delivery enhances axonal rewiring and improves performance after spinal cord injury.

The failure of long descending pathways to regenerate after spinal cord injury (SCI) is generally attributed to inhibitory proteins associated with the glial scar and myelin, or to the loss of neurons' intrinsic capacity to grow, or both. Here, we describe the use of hydrogels as a novel way to deliver molecules that promote axon growth in the injured CNS of adult rats. This method utilizes an injectable liquid polymer solution that crosslinks into a biodegradable, water-swollen hydrogel when photoactivated under visible light. Neurotrophin-3 (NT-3), a trophic factor known to act on corticospinal tract (CST) projection neurons, was used as a prototypic pro-regenerative molecule. Hydrogel release properties were established in vitro to ensure long-term, sustained NT-3 release over a 2-week period; this avoided the need for multiple injections or minipump implantation. Hydrogel/NT-3-treated animals showed improved recovery in the open-field BBB test and in a horizontal ladder walk test compared to controls implanted with hydrogel alone. At the anatomical level, hydrogel/NT-3-treated animals showed far greater axon growth than controls in two major descending pathways for motor control, the CST and the raphespinal tract. In the case of the CST, much of the NT-3-induced growth represented collateral branching from undamaged ventral CST fibers. These studies demonstrate the effectiveness of hydrogel technology as a clinically feasible delivery system to promote regeneration and enhance functional outcome after spinal cord injury.