BACKGROUND: Cerebral injury in adult mammals can induce neural precursor cells (NPCs) to proliferate and migrate towards the focal zone,but it is unclear whether endogenous NPCs can migrate towards regions distal to the hemorrhagic focus or whether NPCs differentiate in the peripheral hemorrhagic region.OBJECTIVE: To investigate the distribution of endogenous NPCs in different brain regions of rats with experimental cerebral hemorrhage,as well as NPC proliferation and differentiation with time.DESIGN,TIME AND SETTING: A randomized,controlled animal experiment was performed at the Department of Neurobiology,Luzhou Medical College,between January 2007 and October 2008.MATERIALS: Bromodeoxyuridine (BrdU) was purchased from Roche,Germany.Mouse antirat BrdU monoclonal antibody,rabbit anti-nestin polyclonal antibody,rabbit antineuron specific enolase (NSE) polyclonal antibody were purchased from Wuhan Boster,China.Rabbit antiglial fibrillary acidic protein (GFAP) polyclonal antibody was purchased from Sigma,USA.METHODS: Thirty-five adult Sprague Dawley rats were randomly divided into three groups: (1) cerebral hemorrhage group (n = 25),rats were stereotaxically administered 50 μL autologous arterial blood via the dorsal caudate putamen to induce cerebral hemorrhage;(2) sham-surgery group (n = 5),rats underwent surgery but did not receive blood injection;(3) blank control group (n = 5),rats received no surgery and blood administration.At 2 hours after surgery,all rats were intraperitoneally administered BrdU.MAIN OUTCOME MEASURES: Distribution and proliferation of BrdU-positive cells were observed by immunohistochemical staining.BrdU-positive cell differentiation into neurons and glial cells in the peripheral hemorrhagic region was detected by double-label immunofluorescence.RESULTS: Immunohistochemistry results revealed that BrdU-positive cells existed not only in the peripheral hemorrhagic region,such as the subependymal layer and hippocampal dentate gyrus,but also in the lateral septal nucleus,diagonal band,habenular nucleus,and cerebral cortex.Following cerebral hemorrhage,BrdU-positive cells in the peripheral hemorrhagic region gradually in-creased (P < 0.05),and peaked at 7-14 days.Double-label immunofluorescence showed that with time after cerebral hemorrhage,BrdU/nestin-positive cells decreased,but BrdU/GFAPand BrdU/NSE-positive cells increased in the peripheral cerebral hemorrhagic region (P< 0.05).CONCLUSION: Cerebral hemorrhage can induce the proliferation of endogenous NPCs,which peaks at 1-2 weeks after hemorrhage.NPCs can also migrate towards the regions distal to the hemorrhagic focus,such as a diagonal band or lateral septal nucleus.NPCs can gradually differentiate with increasing time after hemorrhage. BACKGROUND: Cerebral injury in adult mammals can induce neural precursor cells (NPCs) to proliferate and migrate toward the focal zone, but it is unclear whether endogenous NPCs can migrate to regions distal to the hemorrhagic focus or whether NPCs differentiate in the peripheral hemorrhagic region. OBJECTIVE: To investigate the distribution of endogenous NPCs in different brain regions of rats with experimental cerebral hemorrhage, as well as NPC proliferation and differentiation with time. DESIGN, TIME AND SETTING: A randomized, controlled animal experiment was performed at the Department of Neurobiology, Luzhou Medical College, between January 2007 and October 2008. MATERIALS: Bromodeoxyuridine (BrdU) was purchased from Roche, Germany. Mouse antirat BrdU monoclonal antibody, rabbit anti-nestin polyclonal antibody, rabbit antineuron specific enolase (NSE) polyclonal antibody were purchased from Wuhan Boster, China. Rabbit antiglial fibrillary acidic protein (GFAP) polyclonal antibody was purc hased from Sigma, USA.METHODS: Thirty-five adult Sprague Dawley rats were divided into three groups: (1) cerebral hemorrhage group (n = 25), mice were stereotaxically administered 50 μL of autologous arterial blood via the dorsal caudate putamen to induce (2) sham-surgery group (n = 5), rats underwent surgery but did not receive blood injection; (3) blank control group (n = 5), rats received no surgery and blood administration. At 2 hours after surgery, all rats were intraperitoneally administered BrdU.MAIN OUTCOME MEASURES: Distribution and proliferation of BrdU-positive cells were observed by immunohistochemical staining. BrdU-positive cell differentiation into neurons and glial cells in the peripheral hemorrhagic region was detected by double-label immunofluorescence. RESULTS: Immunohistochemistry results revealed that BrdU-positive cells were not only in the peripheral hemorrhagic region, such as the subependymal layer and hippocampal dentate gyrus, but also in t he lateral septal nucleus, diagonal band, habenular nucleus, and cerebral cortex .Following cerebral hemorrhage, BrdU-positive cells in the peripheral hemorrhagic region gradually in-creased (P <0.05), and peaked at 7-14 days. Double-label immunofluorescence showed that with time after cerebral hemorrhage, BrdU / nestin-positive cells decreased but but BrdU / GFAP and BrdU / NSE-positive cells increased in the peripheral cerebral hemorrhagic region (P <0.05) .CONCLUSION: Cerebral hemorrhage can induce the proliferation of endogenous NPCs , which peaks at 1-2 weeks after hemorrhage. NPCs can also migrate towards the regions distal to the hemorrhagic focus, such as a diagonal band or lateral septal nucleus. NPCs can gradually differentiate with increasing time after hemorrhage.