Expression of hippocampal toll-like receptors 4 and proliferation of neural progenitor cells in mouse model of traumatic brain injury

Abstract

Objective To investigate the expression of hippocampal toll-like receptors 4 (TLR4) and the proliferation of neural progenitor cells (NPCs) in mouse model of traumatic brain injury (TBI).Methods Adult male Balb/c mice were randomly divided into the sham groups and the 1st,3rd,7th,14th,21st days post-traumatic groups.The TBI mouse model was induced by Mamarou weight-drop device.NPCs were labeled with thymidine analog 5-Bromo-2-deoxyUridine (BrdU).The expression and distribution of BrdU and TLR4 in hippocampus were observed by inmmunofluorescence.The expression of TLR4 in protein level was detected by Western-blot.Results It was observed that TLR4 expressed on the NPCs in hippocampus by double-labeling inmmunofluorescence,and the expression of TLR4 protein in hippocampus raised at the 1st day,got to the peak around the 3rd day,then decreased over the 7th day,14th day,and 21st day to a lower value but still higher than the sham group(P ＜ 0.05).NPCs increased at the 1st post-traumatic day,reached the peak at the 3rd day,followed by a gradual reduction from the 3rd day to the 21st day when maintained a higher number than that of the sham group (P ＜ 0.05).Conclusions TLR4 expressed on the NPCs in hippocampus,and the expression of hippocampal TLR4 varied in a similar temporal pattern with the proliferation of NPCs after injury.It suggested that hippocampal TLR4 might play a potential role in the endogenous neurogenesis after TBI. Key words: Craniocerebral trauma; Toll-like receptors 4; Neural progenitor cells