Effect Of PGRN On Proliferation And Differentiation Of Neural Stem Cells After Cerebral Ischemia

Brain ischemia is a cerebrovascular disease which threatens human heath.Acute cerebral lesions after ischemia are divided into ischemic core and penumbra.Rescuing cells from apoptosis in penumabra,and promting neurogenesis are the major strategies after brain ischemia.Neurogenesis is sustained throughout adulthood in the subventricular zone(SVZ)and subgranular zone(SGZ)of mammalian brain.It has been reported that many factors such as cytokines,growth factors and neurotransmitters,which play important roles in proliferation and differentiation process of neural stem cell after brain ischemia.PGRN(progranulin)has been reported to be a mitogenic,neurotropic and anti-inflammatory protein.Previous studies showed that PGRN promoted neural cell lines to differentiate into neurons.PGRN could protect aginast cerebral ischemia injury by inhibition of the inflammatory response,reducing the blood-brain barrier damage and neuroprotection.Thus,PGRN may involve in the neurogenesis and neuroprotection after cerebral ischemia.As so far,the effect of PGRN in neurogenesis after cerebral ischemia has not been reported.We hypothesized that PGRN may involve in pathophysiological process of brain ischemia and promte nerogenesis after cerebral ischemia.In the present study,MCAo models were induced in C57BL/6 mice,mRNA and protein levels of progranulin expression were detected within the ischemic penumbra at 1d,3d,7d after MCAo in both gender of mice.Then,we explored the neuroprotection effect of intracerebroventricular administration of recombinant mouse PGRN in ischemic mice by detecting volume of cerebral infarction and neuronal function evaluation.Finally,we observed the influences of PGRN on neural stem cells proliferation,and differentiation by immunohistochemistry and double immunofluorescence staining.Results:1.PGRN expression in ischemic penumbra after brain ischemia:Real time PCR results showed that the expression of PGRN mRNA was obviously upregulated at 3d,7d after ischemia compared to the sham group in both genders(P<0.01),and there was a significant difference between males and females at 7d after ischemia(P<0.01).The expression of PGRN protein was obviously downregulated at 3d(P<0.05),7d(P<0.01)after ischemia,and there was no gender difference at all time points.2.The neuroprotective effect of PGRN after focal cerebral ischemia:1ng PGRN obviously reduced the infarction volume,enhanced nueronal function at 24 h after ischemia compared with other group in different doses of PGRN(PBS,0.3ng,lng,5ng).3.Cell proliferation in SVZ after PGRN injection in mice MCAo models:The immunohistochemistry staining demonstrated that BrdU and Ki-67 positive cells in SVZ were significantly increased at 3d(P<0.05),7d(P<0.01)after PGRN injection in mice MACo models.4.Cell differentiation after PGRN injection after cerebral ischemia:double labeling immunofluorescence staining showed that BrdU+/DCX+ positive cells proportion in SVZ at 14d after ischemia were significantly increased(P<0.01),and BrdU+/NeuN+positive cells proportion in SVZ were increased at 28d after PGRN injection after ischemia(P<0.05).There is no significantly difference on BrdU+/GFAP+ positive cells in PGRN group compared to controls.Conclusions1.The expression of PGRN mRNA in ischemic penumbra was obviously upregulated in both genders,but the expression of PGRN mRNA in females were lower than males at 7d after ischemia.The protein levels of PGRN were obviously downregulated in males and females,and there is no signicantly difference between genders.2.Cerebral infarction volume was reduced,and the neural function was enhanced by lng PGRN injection after MCAo,which confirmed that PGRN has the protective function in cerebral ischemia.3.PGRN promoted the stem/progenitor cells proliferation in SVZ after cerebral ischemia.PGRN aslo promoted stem/progenitor cells to differentiate into neural precursor cells.PGRN increased the proportion of mature neuron in striatum peri-infarction.