4D imaging analysis of the aging mouse neural stem cell niche reveals a dramatic loss of progenitor cell dynamism regulated by the RHO-ROCK pathway

In the adult ventricular-subventricular zone (V-SVZ), neural stem cells (NSCs) give rise to transit-amplifying progenitor (TAP) cells. These progenitors reside in different subniche locations, implying that cell movement must accompany lineage progression, but the dynamic behaviors of adult NSCs and TAPs remain largely unexplored. Here, we performed live time-lapse imaging with computer-based image analysis of young and aged 3D V-SVZ wholemounts from transgenic mice with fluorescently distinguished NSCs and TAP cells. Young V-SVZ progenitors are highly dynamic, with regular process outgrowth and retraction and cell migration. However, these activities dramatically declined with age. An examination of single-cell RNA sequencing (RNA-seq) data revealed age-associated changes in the Rho-Rock pathway that are important for cell motility. Applying a small molecule to inhibit ROCK transformed young into old V-SVZ progenitor cell dynamic behaviors. Hence RHO-ROCK signaling is critical for normal adult NSC and TAP movement and interactions, which are compromised with age, concomitant with the loss of regenerative ability.