Ultrastructural evidence of mucus I human conjunctival epithelial cultures

Purpose. To demonstrate by ultrastructural techniques that human conjunctiv al epithelium cells in vitro can produce mucin-like secretion. Methods. Primary cultures of human conjunctival epithelial cells were grown in different culture media. Cultures were allowed to grow and were process ed after 5 days and 1, 2, 3, 4, or 5 weeks for transmission and scanning el ectron microscopy, according to the method of Nichols et al. modified in ou r laboratory. Results. Marked differences were seen between primary cultures grown with o r without hydrocortisone. A thick tannic acid-stained layer was observed wh en hydrocortisone was present in the culture medium; however, that layer wa s virtually absent in cultures grown with hydrocortisone-free media. Scanni ng electron microscopy revealed a dense deposit showing a network-like stru cture. Moreover, the age of the cultures clearly influenced the thickness o f the tannic acid-stained deposit, which thickened as the cultures aged. Conclusions. These results strongly suggest that the layer growing in the p resence of hydrocortisone is mucus. The fact that this material became more abundant as the cultures aged indicates that mucus is actively produced an d secreted by conjunctival epithelial cells in vitro. This study might cont ribute to the knowledge of mucus-deficient pathologies of the ocular surfac e.