Detection and localization of the hydrophobic surfactant proteins B and C in human tear fluid and the human lacrimal system.
OBJECTIVE
To evaluate the expression and presence of the surfactant proteins (SP) B and C in the lacrimal apparatus at the ocular surface and in tear fluid.


METHODS
Expression of SP-B and SP-C was analyzed by RT-PCR in healthy lacrimal gland, conjunctiva, meibomian gland, accessory lacrimal glands, cornea, and nasolacrimal ducts. The deposition of the hydrophobic proteins SP-B and SP-C was determined by Western blot and immunohistochemistry in healthy tissues, tear fluid, and aqueous humor.


RESULTS
The presence of both SP-B and SP-C on mRNA and protein level was evidenced in healthy human lacrimal gland, conjunctiva, cornea, and nasolacrimal ducts. Moreover, both proteins were present in tear fluid but were absent in aqueous humor. Immunohistochemical investigations revealed production of both peptides by acinar epithelial cells of the lacrimal gland and additionally by accessory lacrimal glands of the eyelid as well as epithelial cells of the conjunctiva and nasolacrimal ducts. Immunohistochemically, healthy cornea and goblet cells revealed no reactivity.


CONCLUSIONS
Besides the recently detected surfactant-associated proteins SP-A and SP-D, our results show that SP-B and SP-C are also peptides of the tear film, the ocular surface, and the lacrimal apparatus. Based on the current knowledge of lowering surface tension in alveolar lung cells, a similar effect of SP-B and SP-C may be assumed concerning the tear film.
Bräuer
Lars
L
Department of Anatomy and Cell Biology, Martin Luther University of Halle-Wittenberg, Halle/Saale, Germany. lars.braeuer@medizin.uni-halle.de
Johl
Madeleine
M
Börgermann
Jochen
J
Pleyer
Uwe
U
Tsokos
Michael
M
Paulsen
Friedrich P
FP
D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D003228:Conjunctiva / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism; D005260:Female; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007124:Immunoenzyme Techniques; D007765:Lacrimal Apparatus / Q000378:metabolism*; D008297:Male; D008537:Meibomian Glands / Q000378:metabolism; D008875:Middle Aged; D009301:Nasolacrimal Duct / Q000378:metabolism*; D037701:Pulmonary Surfactant-Associated Protein B / Q000235:genetics / Q000378:metabolism*; D037721:Pulmonary Surfactant-Associated Protein C / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013666:Tears / Q000378:metabolism*
D037701:Pulmonary Surfactant-Associated Protein B; D037721:Pulmonary Surfactant-Associated Protein C; D012333:RNA, Messenger