Localization of hyaluronan in the human endolymphatic sac. A study using the affinity hyaluronan binding protein

This study was undertaken with the aim of localizing hyaluronan (hyaluronic acid, HYA) in tissue sections of the human endolymphatic sac by use of a hyaluronan-binding affinity protein and the avidin-biotin/peroxidase staining procedure. Five human endolymphatic sacs were removed during surgery for acoustic neuroma. After microwave-aided fixation and decalcification, paraffin-embedded sections were prepared by routine histological methods. HYA was detected in some of the intraluminal substance as well as in parts of the epithelial lining, mainly in the rugose portions of the endolymphatic sac. HYA was observed intracellularly in epithelial cells. It was also found in the subepithelial tissue near the epithelia and close to the bony aqueduct. The distribution of HYA was uneven at all locations. The finding of HYA within the human endolymphatic sac may imply that this substance has important functions in the control of inner ear fluid homeostasis.