Introduction:
In central nervous system, progranulin (PGRN), a glycoprotein growth factor, is considered to play crucial roles in maintaining physiological functions, and mutations in PGRN gene cause TAR DNA-binding protein-43 (TDP-43)-positive frontotemporal lobar degeneration. Although several studies reported that PGRN plays protective roles against ischemic brain injury, it remains unknown the precise mechanisms by which PGRN exerts protective effects on the ischemic brain injury.
Methods:
We determined the temporal changes of expression and localization of PGRN after ischemia as well as therapeutic effects of PGRN on ischemic brain injury using in vitro and in vivo models.
Results:
First, we demonstrated a dynamic change of PGRN expression in ischemic Sprague-Dawley rats, including increased levels of PGRN expression in microglia within the ischemic core, and increased level of PGRN expression in survived neurons as well as induction of PGRN expression in endothelial cells within the ischemic penumbra. Second, we demonstrated that PGRN could protect against acute focal cerebral ischemia by variety of mechanisms including via attenuation of blood-brain barrier disruption, suppression of neuroinflammation, and neuroprotection: we found that PGRN may regulate vascular permeability via vascular endothelial growth factor (VEGF), that PGRN may suppress neuroinflammation after ischemia via anti-inflammatory interleukin-10 (IL-10) in microglia, and that neuroprotective effect of PGRN may be explained in part by inhibition of cytoplasmic redistribution of TDP-43 using PGRN knock-out mice (C57Bl/6 background). Finally, we demonstrated the therapeutic potential of PGRN against acute focal cerebral ischemia using a rat autologous thromboembolic model with delayed tissue plasminogen activator (tPA) treatment. Intravenously administered recombinant PGRN reduced volumes of cerebral infarct and edema, suppressed hemorrhagic transformation, and improved motor outcome (P = 0.007, 0.038, 0.007, and 0.004, respectively).
Conclusions:
PGRN may be a novel therapeutic target that provides vascular protection, anti-neuroinflammation, and neuroprotection related in part to VEGF, IL-10, and TDP-43, respectively.
Multiple therapeutic effects of a growth factor, progranulin on ischemic brain injury