Comparative anatomy of the human and canine efferent tear duct system--impact of mucin MUC5AC on lacrimal drainage.
OBJECTIVE
To investigate the histomorphology of the canine tear drainage system and to show the distribution of mucin MUC5AC within the tissue.


METHODS
Conjunctiva and tear drainage systems of 19 long-nosed dogs were investigated histologically and ultrastructurally. The tissues were stained with eight different antibodies reactive against less glycosylated and highly-glycosylated MUC5AC. Results were compared with findings in human tissue received from 12 body donors.


RESULTS
Except for a distinctly longer nasolacrimal duct and several accessory openings of the duct into the nasal cavity, the morphology of the canine tear drainage system is very similar to that of humans. MUC5AC in less- and highly-glycosylated forms was present in the conjunctival tissue of dogs as well of humans. Within the tear sac and the nasolacrimal duct only less-glycosylated MUC5AC could be found in dogs and in human.


CONCLUSIONS
These findings demonstrate that the canine tear drainage system is very similar to its human equivalent. In particular the distribution of MUC5AC, supposed to play an important role within the pathogenesis of dry eye syndrome (DES), is the same as in humans. Therefore the canine model seems to be an appropriate model for further DES research.
Department of Otorhinolaryngology, Head and Neck Surgery, Dessau Hospital, Dessau, Germany.
Roman
R
Hirt
Ozan Y
OY
Tektas
Stephen D
SD
Carrington
Richard
R
Arnett
Eamonn
E
FitzPatrick
Stephan
S
Knipping
Friedrich P
FP
Paulsen
D000368:Aged; D000369:Aged, 80 and over; D000717:Anatomy, Comparative; D000818:Animals; D003228:Conjunctiva / Q000378:metabolism / Q000648:ultrastructure; D004285:Dogs; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007765:Lacrimal Apparatus / Q000033:anatomy & histology* / Q000378:metabolism; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D055271:Mucin 5AC / Q000378:metabolism*; D009301:Nasolacrimal Duct / Q000378:metabolism / Q000648:ultrastructure; D013666:Tears / Q000378:metabolism*
C524678:MUC5AC protein, human; D055271:Mucin 5AC