Regulation of fractone heparan sulfate composition in young and aged subventricular zone neurogenic niches.

Fractones, specialized extracellular matrix structures found in the subventricular zone (SVZ) neurogenic niche, can capture growth factors, such as basic fibroblast growth factor, from the extracellular milieu through a heparin-binding mechanism for neural stem cell (NSC) presentation, which promotes neurogenesis. During aging, a decline in neurogenesis correlates with a change in the composition of heparan sulfate (HS) within fractones. In this study, we used antibodies that recognize specific short oligosaccharides with varying sulfation to evaluate the HS composition in fractones in young and aged brains. To further understand the conditions that regulate 6-O sulfation levels and its impact on neurogenesis, we used endosulfatase Sulf1 and Sulf2 double knockout (DKO) mice. Fractones in the SVZ of Sulf1/2 DKO mice showed immunoreactivity for the HS epitope, suggesting higher 6-O sulfation. While neurogenesis declined in the aged SVZ of both wild-type and Sulf1/2 DKO mice, we observed a larger number of neuroblasts in the young and aged SVZ of Sulf1/2 DKO mice. Together, these results show that the removal of 6-O-sulfation in fractones HS by endosulfatases inhibits neurogenesis in the SVZ. Our findings advance the current understanding regarding the extracellular environment that is best suited for NSCs to thrive, which is critical for the design of future stem cell therapies.