Stroke-induced neurogenesis in aged brain.
OBJECTIVE
Stroke induced by middle cerebral artery occlusion (MCAO) triggers increased neurogenesis in the damaged striatum and nondamaged hippocampus of young adult rodents. We explored whether stroke influences neurogenesis similarly in the aged brain.


METHODS
Young adult (3 months) and old (15 months) rats were subjected to 1 hour of MCAO, and new cells were labeled by intraperitoneal injection of 5-bromo-2'-deoxyuridine 5'-monophosphate (BrdU), a marker for dividing cells, for 2 weeks thereafter. Animals were euthanized at 7 weeks after the insult, and neurogenesis was assessed immunocytochemically with antibodies against BrdU and neuronal markers with epifluorescence or confocal microscopy.


RESULTS
Young and old rats exhibited the same increased numbers of new striatal neurons after stroke, despite basal cell proliferation in the subventricular zone being reduced in the aged brain. In contrast, both the number of stroke-generated granule cells and basal neurogenesis in the dentate subgranular zone were lower in old compared with young animals. Also, the ability of newly formed cells to differentiate into neurons was impaired in the aged dentate gyrus.


CONCLUSIONS
Basal neurogenesis is impaired in the subgranular and subventricular zones of aged animals, but both regions react to stroke with increased formation of new neurons. The magnitude of striatal neurogenesis after stroke is similar in young and old animals, indicating that this potential mechanism for self-repair also operates in the aged brain.
Laboratory of Neural Stem Cell Biology, University Hospital, The Lund Strategic Research Center for Stem Cell Biology and Cell Therapy, Lund, Sweden.
Vladimer
V
Darsalia
Ursula
U
Heldmann
Olle
O
Lindvall
Zaal
Z
Kokaia
D000375:Aging; D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology*; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002452:Cell Count; D002454:Cell Differentiation; D049109:Cell Proliferation; D002536:Cerebral Arteries / Q000473:pathology; D018891:Dentate Gyrus / Q000473:pathology; D005260:Female; D006624:Hippocampus / Q000378:metabolism; D007150:Immunohistochemistry; D020244:Infarction, Middle Cerebral Artery; D007274:Injections, Intraperitoneal; D007511:Ischemia / Q000473:pathology; D019394:Ki-67 Antigen / Q000096:biosynthesis; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013234:Stem Cells / Q000166:cytology; D020521:Stroke / Q000473:pathology*; D013997:Time Factors
D019394:Ki-67 Antigen; D001973:Bromodeoxyuridine