Activation of endogenous neural stem cells in the adult human brain following subarachnoid hemorrhage

In the adult human brain, the presence of neural stem cells has been documented in the subgranular layer of the dentate gyrus of the hippocampus and in the subventricular zone of the lateral ventricles. Neurogenesis has also been reported in rodent models of ischemic stroke, traumatic brain injury, epileptic seizures, and intracerebral or subarachnoid hemorrhage. However, only sparse information is available about the occurrence of neurogenesis in the human brain under similar pathological conditions. In the present report, we describe neural progenitor cell proliferation in the brain of patients suffering from subarachnoid hemorrhage (SAH) resulting from ruptured aneurysm. Ten cerebral samples from both SAH and control patients obtained, respectively, during aneurysm clipping and deep brain tumor removal were analyzed by reverse transcription followed by polymerase chain reaction (RT‐PCR) and/or immunohistochemistry (IHC). In tissue specimens from SAH patients, RT‐PCR and IHC revealed the expression of a variety of markers consistent with CNS progenitor cells, including nestin, vimentin, SOX‐2, and Musashi1 and ‐2. In the same specimens, double immunohistochemistry followed by confocal analysis revealed that Musashi2 consistently colocalized with the proliferation marker Ki67. By contrast, no such gene or protein expression profiles were detected in any of the control specimens. Thus, activation of neural progenitor cell proliferation may occur in adult human brain following subarachnoid hemorrhage, possibly contributing to the promotion of spontaneous recovery, in this pathological condition. © 2007 Wiley‐Liss, Inc.