Inducible Pluripotent Stem Cell-Derived Small Extracellular Vesicles Rejuvenate Senescent Blood–Brain Barrier to Protect against Ischemic Stroke in Aged Mice

Blood–brain barrier (BBB) breakdown after ischemic
stroke
exacerbates brain injury and BBB senescence can cause severe neurological
deficits in aged ischemic stroke population. Recent evidence reveals
that inducible pluripotent stem cell-derived small extracellular vesicles
(iPSC-sEVs) possess phenomenal antisenescence capability. However,
whether iPSC-sEVs can rejuvenate BBB senescence to improve stroke
outcomes in aged mice remains unknown. Here, we showed that long-term
treatment with iPSC-sEVs alleviated aging-induced BBB senescence in
aged mice. In aged stroke mice, iPSC-sEVs significantly mitigated
BBB integrity damage, reduced the following infiltration of peripheral
leukocytes, and decreased the release of pro-inflammatory factors
from the leukocytes, which ultimately inhibited neuronal death and
improved neurofunctional recovery. Mechanism studies showed that iPSC-sEVs
could activate the endothelial nitric oxide synthase (eNOS) and up-regulate
sirtuin 1 (Sirt1) in senescent endothelial cells. Blocking the activation
of eNOS abolished iPSC-sEV-mediated rejuvenation of BBB senescence
and the protection of BBB integrity. Proteomics results demonstrated
that iPSC-sEVs were enriched with bioactive factors including AKT
serine/threonine kinase 1 (AKT1) and calmodulin (CALM) to activate
the eNOS–Sirt1 axis. Further investigation showed that AKT1
and CALM inhibitors blocked iPSC-sEV-afforded activation of the eNOS–Sirt1
axis in senescent endothelial cells. Taken together, iPSC-sEVs can
protect against ischemic stroke in aged mice by rejuvenating BBB senescence,
partially, through delivering AKT1 and CALM to activate eNOS–Sirt1
axis, which indicates that iPSC-sEVs treatment is an effective alternative
to treat ischemic stroke in the aged population.