Research

Neuronal precursor cell proliferation in the hippocampus after transient cerebral ischemia: a comparative study of two rat strains using stereological tools

Jesper Kelsen^1,2,3 , Marianne H Larsen⁴ , Jens Christian Sørensen^2,5 , Arne Møller^2,6 , Jørgen Frøkiær^1,2 , Søren Nielsen^1,7 , Jens R Nyengaard^2,8 , Jens D Mikkelsen⁹ and Lars Christian B Rønn¹⁰

¹  The Water and Salt Research Centre, University of Aarhus, DK-8000 Aarhus C, Denmark

²  Institute of Clinical Medicine, University Hospital of Aarhus, Brendstrupgaardsvej 100, DK-8200 Aarhus N, Denmark

³  Department of Neurosurgery, University Hospital of Copenhagen (Rigshospitalet), Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark

⁴  Department of Neuroscience and Pharmacology, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark

⁵  Department of Neurosurgery, University Hospital of Aarhus, Nørrebrogade 44, DK-8000 Aarhus C, Denmark

⁶  PET-centre, University Hospital of Aarhus, Nørrebrogade 44, DK-8000 Aarhus C, Denmark

⁷  Department of Cell Biology, Institute of Anatomy, Building 1230, University of Aarhus, DK-8000 Aarhus C, Denmark

⁸  Stereology and Electron Microscopy Research Laboratory and MIND Center, Danish Neuroscience Centre, University Hospital of Aarhus, Nørrebrogade 44, DK-8000 Aarhus C, Denmark

⁹  Neurobiology Research Unit, University Hospital of Copenhagen (Rigshospitalet), Building 9201, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark

¹⁰  NEUROSEARCH A/S, Pederstrupvej 93, DK-2750 Ballerup, Denmark

author email corresponding author email

Experimental & Translational Stroke Medicine 2010, 2:8doi:10.1186/2040-7378-2-8

Published:	6 April 2010

Abstract

Background

We are currently investigating microglial activation and neuronal precursor cell (NPC) proliferation after transient middle cerebral artery occlusion (tMCAo) in rats. This study aimed: (1) to investigate differences in hippocampal NPC proliferation in outbred male spontaneously hypertensive rats (SHRs) and Sprague-Dawley rats (SDs) one week after tMCAo; (2) to present the practical use of the optical fractionator and 2D nucleator in stereological brain tissue analyses; and (3) to report our experiences with an intraluminal tMCAo model where the occluding filament is advanced 22 mm beyond the carotid bifurcation and the common carotid artery is clamped during tMCAo.

Methods

Twenty-three SDs and twenty SHRs were randomized into four groups subjected to 90 minutes tMCAo or sham. BrdU (50 mg/kg) was administered intraperitoneally twice daily on Day 4 to 7 after surgery. On Day 8 all animals were euthanized. NeuN-stained tissue sections were used for brain and infarct volume estimation with the 2D nucleator and Cavalieri principle. Brains were studied for the presence of activated microglia (ED-1) and hippocampal BrdU incorporation using the optical fractionator.

Results

We found no significant difference or increase in post-ischemic NPC proliferation between the two strains. However, the response to remote ischemia may differ between SDs and SHRs. In three animals increased post-stroke NPC proliferation was associated with hippocampal ischemic injury. The mean infarct volume was 89.2 ± 76.1 mm³ in SHRs and 16.9 ± 22.7 mm³ in SDs (p < 0.005). Eight out of eleven SHRs had ischemic neocortical damage in contrast to only one out of 12 SDs. We observed involvement of the anterior choroidal and hypothalamic arteries in several animals from both strains and the anterior cerebral artery in two SHRs.

Conclusions

We found no evidence of an early hippocampal NPC proliferation one week after tMCAo in both strains. Infarction within the anterior choroidal artery could induce hippocampal ischemia and increase NPC proliferation profoundly. NPC proliferation was not aggravated by the presence of activated microglia. Intraluminal tMCAo in SHRs gave a more reliable infarct with neocortical involvement, but affected territories supplied by the anterior cerebral, anterior choroidal and hypothalamic arteries.