Eosinophilic Substance is “Not Amyloid” in the Mouse Nasal Septum

Abstract

An eosinophilic substance (ES) is usually observed in the mouse nasal septum and increases in volume with aging. It has been described as amyloid in textbooks and one report. However, it has been described as "not amyloid" in other reports because there was a negative reaction to Congo red. In this study, the ES was investigated histopathologically and electron microscopically to determine whether it was amyloid or not. The ES was only observed at the interstitium of clear HE-stained nasal glands in the septum, in which 2 kinds of glands were present (dark and clear stained by HE). The volume of the ES was small in young mice and large in older ones. Neither nasal gland degeneration nor inflammation resulted, even if a large amount of the ES was observed. The ES reacted negatively to Congo red but was strongly positive to periodic acid-Schiff reaction with prior diastase treatment. In the electron microscope observation, the ES consisted of amorphous material and collagen, but no nonbranching fibrils. Similar amorphous material was also observed in the nasal gland epithelial cells and was connected to the material in the rough endoplasmic reticulum. The above-mentioned findings indicated that the ES was not amyloid and suggested the ES might consist of not only collagen but also complex carbohydrate, which was produced by the nasal gland epithelial cells.

Deposition Process of Eosinophilic Substance in Mouse Nasal Septum

“…Furthermore, AM was not only very similar to the material in the rough endoplasmic reticulum of the clear HE-stained nasal gland epithelial cells, it was also connected to it. These findings suggested that the clear HE-stained nasal gland epithelial cells produced AM [1].It is not clear how AM produced by clear HE-stained nasal gland epithelial cells deposits in the interstitium. In this study, we investigated the deposition process histopathologically and electron microscopically.…”

“…ES deposited at the interstitium of the clear HEstained nasal glands only. Electron microscopically, AM was observed in the clear HE-stained nasal gland epithelial cells as well as in the interstitium [1]. Glands composed of nasal gland epithelial cells holding AM were also observed in areas without interstitial AM nearby.…”

“…Our previous report revealed that ES is not amyloid because it reacted negatively to Congo red and there were no nonbranching fibrils in the electron microscope examination [1]. Moreover, ES consisted of collagen and an amorphous material (AM), suggesting that AM is a complex carbohydrate except for the osteoglycan, because ES reacted positively with periodic acid Schiff reaction with prior diastase treatment, and negatively with toluidine blue and alcian blue [1].In the previous study, two kinds of glands were observed in the nasal septum in mice [1]. One of them stained clear with hematoxylin and eosin (HE), the other stained dark with HE.…”

“…ES has been described as amyloid in textbooks [5,7], but there are a few descriptions that ES is not amyloid [4,8]. Our previous report revealed that ES is not amyloid because it reacted negatively to Congo red and there were no nonbranching fibrils in the electron microscope examination [1]. Moreover, ES consisted of collagen and an amorphous material (AM), suggesting that AM is a complex carbohydrate except for the osteoglycan, because ES reacted positively with periodic acid Schiff reaction with prior diastase treatment, and negatively with toluidine blue and alcian blue [1].…”

“…In the previous study, two kinds of glands were observed in the nasal septum in mice [1]. One of them stained clear with hematoxylin and eosin (HE), the other stained dark with HE.…”