Mucosal mast cells of the rat intestine: a re-evaluation of fixation and staining properties, with special reference to protein blocking and solubility of the granular glycosaminoglycan

Abstract

Mucosal mast cells of the gastrointestinal tract constitute a separate cell line within the mast cell system of the rat, differing in several respects from the classical connective tissue mast cells and, unlike the latter, requiring special fixation techniques for their demonstration. We have examined some histochemical properties of mucosal mast cells of the duodenum and compared them with connective tissue mast cells of the tongue or skin. The results indicate that the structural integrity of the granules of both types of mast cell is partly dependent on ionic linkages between glycosaminoglycan and protein. The so far unidentified glycosaminoglycan of mucosal mast cells appears to be more soluble than the heparin of connective tissue mast cells. The strongly fluorescent binding of Berberine to the granules of connective tissue mast cells and, depending on their content, of heparin is absent from mucosal mast cells, confirming previous findings which suggested that they contain a glycosaminoglycan with a lower degree of sulphation. Aldehyde fixation by routine procedures reversibly blocks the cationic dye binding of mucosal mast cell granules. The dye binding groups may be unmasked by trypsination or by long staining times of the order of several days. The results suggest that the blocking of staining by aldehydes is caused by a diffusion barrier of a protein nature. Mucosal and connective tissue mast cells thus differ with respect to the spatial arrangement of glycosaminoglycan and protein in their granules. As a result of the study a modified method for the demonstration of mucosal mast cells in tissue sections is described, based on normal formaldehyde fixation and staining in Toluidine Blue for a long time. It has some advantages over previous methods and preserves the structure of mucosal and connective tissue mast cells equally well.

Mast cells: the forgotten cells of renal fibrosis

“…The formalin sensitivity of traditional histochemical stains for mast cells, such as toluidine blue and alcian blue, has long been recognised 59 and prevents the accurate quantification of mast cells in routinely processed tissue. Our initial quantification of toluidine blue stained mast cells in nephrectomy specimens indicates that around 75% of renal mast cells are formalin sensitive.…”

Mast cells in the swimbladder of Atlantic salmon Salmo salar:histochemistry and responses to compound 48/80 and formalin-inactivated Aeromonas salmonicida

“…Mast cells of the Atlantic salmon swimbladder resemble mammalian mucosal mast cells, both in their staining properties and their susceptibility to fixatives. The glycosaminoglycan component of the granules of mucosal mast cells, which is responsible for the specific metachromatic dye-binding, can become extracted during fixation, or the dye-binding groups blocked by aldehydes (Wingren & Enerback 1983).…”

Tissue-dependent differences in the asynchronous appearance of mast cells in normal mice and in congenic mast cell-deficient mice after infusion of normal bone marrow cells

“…In addition, the studies show that the introduction of a bolus of normal bone marrow progenitors in W = W v mice results in mast cell densities in the studied tissues that do not mimic those of W v mice, as well as the mast cell density in several other sites at 15 weeks after bone marrow infusion. The data in that study were obtained from tissues fixed in 10% neutral buffered formalin, which is not suitable for the subsequent staining of mucosal mast cells with cationic dyes [1][2][3]. In addition, the data were derived by determining the ratio between mast cell numbers and tissue sample length, a semiquantitative method.…”