Postoperative cognitive dysfunction (POCD) is one of the most common complications after surgery under general anesthesia and usually manifests as newly presented cognitive impairment. However, the mechanism of POCD is still unclear. In addition to neurons, glial cells including microglia, astrocytes and oligodendrocytes, represent a large cell population in the nervous system. The bi-directional communication between neurons and glia provides basis for neural circuit function. Recent studies suggest that glial dysfunctions may contribute to the occurrence and progress of POCD. In this paper, we review the relevant work on POCD, which may provide new insights into the mechanism and therapeutic strategy for POCD.
ObjectiveTo illustrate the role of epidermal growth factor (EGF) secreted by astrocytes in the process of tacrolimus (FK506) in promoting neurite outgrowth. MethodsThe spinal cord astrocytes and neuronal cells were isolated respectively from 2-day-old Sprague Dawley (SD) rats and 15-day SD pregnant rats, and cultured in vitro and identified by immunofluorescence staining. The spinal cord astrocytes were cultured with 20 μmol/L FK506 medium in the experimental group, and with FK506 free medium in the control group. The supernatant was collected after 24 hours for preparing conditioned medium, and astrocytes were collected. EGF proteins in the conditioned medium were detected with ELISA, and EGF gene expressions of astrocytes were detected with real-time quantitative PCR (RT-qPCR). The spinal cord neurons were cultured respectively with conditioned medium from the experimental group (FK506-CM) and the control group (C-CM) in group A and group B, also with neutralized C-CM and neutralized FK506-CM with anti-EGF neutralizing antibodies in group C and group D. Both the total neurite length and the longest neurite length were measured and compared among groups. ResultsBoth astrocytes and neurons were confirmed by immunofluorescence staining. The EGF content of experimental group (0.241±0.044) was significantly higher than that of the control group (0.166±0.014) (t=3.93, P=0.01); EGF gene expression of the experimental group (1.12±0.25) was significantly higher than that of the control group (0.46±0.11) (t=5.78, P=0.00). The neurite length measurement displayed that the total neurite length and the longest neurite length of groups C and D were significantly shorter than those of groups A and B (P<0.05). Both the total and longest neurite length of group A were significantly longer than those of group B (P<0.05), but no significant difference was shown between groups C and D (P>0.05). ConclusionThe EGF secreted by spinal cord astrocytes can promote the neurite outgrowth. So spinal cord astrocytes can be used as an important intermediary target of FK506 to promote the recovery of neurological function.