Lysosomal enzymes and mannose 6-phosphate receptors in the lacrimal drainage system: Evidence and its potential implications.

PURPOSE: To investigate the presence and patterns of lysosomal enzymes and mannose 6-phosophate receptor (MPRs) in human lacrimal drainage system. METHODS: The study was performed on healthy lacrimal sacs and nasolacrimal ducts obtained from exenteration samples immediately after surgery and frozen at -80°C for subsequent analysis. Soluble proteins' extract was used for enzyme assays, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE), native PAGE, activity staining, and western blot analysis. Membrane proteins were separately assessed for detection of mannose 6-phosphate receptors, MPR 46. Sepharose gels, 4-methylumbelliferyl substrates, and antibodies against common lysosomal enzymes and MPRs were used. Enzyme assays were carried out in triplicate to ascertain the results. RESULTS: Differential lysosomal enzyme activities were documented, and among them acid phosphatase and ß-hexosaminidase were found to be high. Western blot analysis using enzyme antibodies and subsequent activity staining confirmed strong signals for moderately expressed enzymes such as fucosidase, glucuronidase, and mannosidase. Membrane extracts demonstrated the presence of MPR 46, which indicates the possible roles of cation-dependent MPRs in lysosomal targeting in human lacrimal drainage system. CONCLUSION: This study provides a proof of principle for the presence of differential lysosomal activity and mannose 6-phosphate ligand transport receptors in human lacrimal drainage system and hypothesizes the potential implications of their dysfunctions.

Apoptosis as a creative agent of embryonic development of bucca, mentum and nasolacrimal duct. An in vivo study in rats.

INTRODUCTION: For embryonal facial development several fusion processes between different facial prominences are necessary. If fusion fails to appear, various facial clefts may occur, known as median (e.g. lower median cleft lip), oblique (e.g. open nasolacrimal duct) or lateral facial clefts (macrostomia, lateral cleft). MATERIAL AND METHODS: The development of 3 different facial regions (bucca, mentum, and nasolacrimal duct) was examined in rats using serial histological sections on day 13.5 after conception. Common procedures were used (staining for active caspase-3 and for Ki-67) for histological assessment about the role of apoptotic and proliferative processes in the fusion zones of buccal, mental and nasolacrimal areas. RESULTS: Multiple apoptotic events were detected in epithelial cells of the respective regions, the proliferative centers were located in the mesenchymal surroundings of fusion zones. CONCLUSION: A substantial precondition for fusion of facial prominences are proliferative and apoptotic processes in epithelial and mesenchymal cells. Apoptosis contributes to the development of bucca, mentum and the nasolacrimal duct. Absence of apoptoses may be responsible for facial clefts.