Mucin Secretion and MUC1 mRNA Expression in the Cultured Secretory Cells of the Rat Nasal Epithelium

Kim, Ic Tae

Abstract

The upper respiratory system is lined with epithelium (mucosa) of the pseudostratified ciliated columnar type that produces mucus as a secretion. The major constituent of mucus is mucin, a glycoprotein of distinct physical and biochemical properties that exists in various organs. The aim of this study was to analyze the biochemical and molecular biological conditions affecting mucin secretion in cultured secretory cells of the upper respiratory mucosa. Rat nasal epithelial cells were cultured in four conditions differing in culture matrix : 1) plastic surface (PL), 2) thick collagen gel (TG), 3) thin collagen gel (GC), and 4) collagen gel coated membrane (CO). In each group, cell proliferation patterns, gel lysis and ciliary regeneration were observed, and attachment efficiency and confluence day were recorded. After confluence, mucin in the culture media was tagged with [3H]-glucosamine and analyzed by elution through Sepharose CL-4B column. The expression of MUC1 in cultured cells was analyzed by RT-PCR. In PL and GC, attachment efficiency was less than 2.2%. The shape and size of each cell in active proliferation was not regular. Confluence was observed on culture day 21 (range : 15-24). In TG and CO, attachment efficiency was more than 10.0% and the shape and size of each cell in active proliferation was regular in a compact fashion. Eight days (range : 7-11) were needed for confluence. After elution through column, mucin was detected in TG and CO but not in GC and PL. MUC1 was expressed in TG and CO but not in GC and PL. In conclusion, a thick collagen gel matrix was essential in mucin secretion and MUC1 expression in cultured secretory cells of the rat nasal mucosa.