Opposing blood-contacting surfaces of the human cavernous internal carotid artery: a segmental and topographic immunofluorescence study.

PURPOSE: The cavernous segment of the internal carotid artery (ICA) courses within the cavernous sinus (CS). In this segment, the luminal surface of the intima is in contact with arterial blood, whereas the endothelial covering over its CS-facing outer surface is in contact with cranial venous blood within the CS. Thus, the opposite surfaces of the same arterial wall are associated with different circulatory microenvironments. This study aimed to compare the immunoreactivity distributions of pH sensitive G protein coupled receptor 4 (GPR4) and mechanosensitive PIEZO1 across ICA segments and surfaces.

METHODS: Cavernous and cervical ICA segments from 10 human cadavers embalmed with 10% neutral buffered formalin were dissected. Specimens were routinely processed, paraffin-embedded, and sectioned. Sections underwent GPR4 and PIEZO1 immunofluorescence labeling and laser scanning confocal microscopy.

RESULTS: GPR4 immunoreactivity was detected at the CS-facing outer wall contour of the cavernous ICA in 8/10 cadavers, but not at its luminal surface or in the examined cervical ICA regions. Two-dimensional optical sections and three-dimensional reconstructions demonstrated the signal's topographic and spatial association with this surface. PIEZO1 immunoreactivity was not detected in either segment.

CONCLUSION: In the human ICA, the GPR4 immunoreactivity distribution differed by anatomical segment and vessel surface. PIEZO1 immunoreactivity was not detected in the examined regions. This qualitative observation identifies the outer surface of the cavernous ICA that is associated with cranial venous blood as an anatomical target for further molecular investigation.