Increased Severity of Acute Cerebral Ischemic Injury Correlates with Enhanced Stem Cell Induction as well as with Predictive Behavioral Profiling

An 8-vessel-occlusion (8VO) method was developed to compare with the conventional 4-vessel-occlusion (4VO) in hippocampal ischemic damage and progenitor cell induction 10 days following ischemia in female rats. Eight posture-relevant tests were performed following ischemia to correlate grades of postural abnormality with the histological outcome. The total hippocampal living cell ratio including 7 hippocampal subregions in 8VO group (n=11) was much lower than that in 4VO group (n=10, 51±5% vs. 78±4, p<0.01). In 4VO group, BrdU positive cells were mainly located in the subgranular zone (SGZ) with a count of 54±20 / mm2 (7μ-thick slice), comparable to the maximal level following global ischemia in male gerbils and rats reported so far referring to slice-thickness differences (50-60μ-thick slices). Similarly, nestin-bearing cells were 29±11 / mm2. In 8VO group, BrdU and nestin positive cells increased by 10 times. Triple staining of BrdU, nestin and DAPI demonstrated that BrdU-immunoreactivity was extensively distributed in the hippocampal hilus while the nestin was mainly located along the SGZ. Most of nestin labeling was not co-localized with the BrdU, indicating that establishment of these cells might precede BrdU injections (8 and 9d post ischemia). Behavioral scores were much greater for 8VO group than for 4VO group and composite postural scores well correlated with the hippocampal cell loss. In conclusion, severe ischemia correlates with vigorous induction of the hippocampal progenitor cells in rats while behavioral profiling of posture changes permits prediction of severity of damage.