Research On Gene Expression Change Of The Subventricle Zone Evoked By Ischemia In 3-day Old Rats

As the largest pool of neural stem cells in mammalian animals,the subventricular zone(SVZ) persists through lifetime and retains the potency of self-renewing,cell proliferation and differentiation.After brain ischemia,this potency can be recaptured and neurogenensis be accomplished,which provides a potentially significant therapeutic strategy for ischemic injury not only in adult brain but also in premature brain.A specialized milieu supports neurogenesis and regeneration after injury in SVZ. Stem cells frequently reside in niches that regulate their self-renewal,activation and differentiation.Understanding the molecular components change after ischemia in neural stem cell niche is crucial to delineating the function of neural stem cells and ultimately their therapeutic potential.To investigate the effect of brain ischemia to premature SVZ culture,3-day old Sprague-Dawley rats were employed,both bilateral carotid arteries were occluded for experimental group and rats with unoccluded arteries were used as the control group, the animals were killed at the chosen time points:1 day,4 days,7 days after surgery. After SVZ culture was isolated and RNA be extracted and processed,microarrays containing approximately 28000 known genes were applied to get the data about gene expression change,and three methods were taken to analyse this data bulk: differential expression analysis,cluster analysis based on time series and gene regulatory network based on function similarity and the following results were got:(1) By differential expression analysis,17 genes were found changed in SVZ niche after ischemia,among them,10 were up-regulated and 7 were down-regulated. These genes are associated with multiple fuctions including signal transduction, inflammation and cellular structure,et al.(2)By cluster analysis based on time series,TGFβamong all the genes participated in cell proliferation and apoptosis,was found to take a important role in the gene expression change.We chose TGFβ1 and its downstream protein Smad2 for further verification by Real-Time PCR.It is found that both TGFβand Smad2 mRNA increased at each of three time points,and the peak increase occurred at 7 days after the ischemic injury.(3) In the gene network based on function similarity composed of all the genes in Wnt,TGF,BMP,VEGF pathways,13 were found to act as the hinges,these genes function at different levels in signal pathways in synergism or antagonism.Moreover, they are likely to constitute a part of the key regulators among all the genes participated in the premature SVZ niche change after ischemic injury.