Human GLUT5 immunolabeling is useful for evaluating microglial status in neuropathological study using paraffin sections

In neuropathological studies it is important to detect both resting and reactive microglia in paraffin sections. We examined the usefulness of human (h) GLUT5, a glucose transporter, as a microglial marker. We produced an hGLUT5 antibody against its C-terminal sequence and stained human brain tissue sections. The hGLUT5 antibody consistently stained microglia in cryostat sections. In paraffin sections fixed with formalin, paraformaldehyde or ethanol, both resting and reactive microglia were stained; the latter were stained more intensely than the former. The hGLUT5 and glial fibrillary acidic protein labeling did not overlap each other in double immunofluorescence analyses. Oligodendrocytes, perivascular cells, choroid plexus epithelium and ependymal cell were negative for hGLUT5. Even after 1-month fixation in formalin, the hGLUT5 antibody stained microglia well. Microwave pretreatment enhanced the immunoreactivity of hGLUT5. As compared with other microglial markers, KP-1, KiM1p, CR3.43 and RCA-1, the hGLUT5 antibody could be considered good morphological marker. hGLUT5 immunolabeling clearly showed the detailed microglial processes, whereas immunolabeling with Ki-M1P and KP-1 showed cytoplasmic granules, and it was difficult to trace the microglial processes. The hGLUT5 antibody stained both resting and reactive microglia, whereas CR3.43 stained only reactive microglia, and RCA-1 labeled microvessels more intensely than microglia. Thus, hGLUT5 is a marker that is suitable for routine histopathological staining procedures.