Transforming growth factor-β/Smad - signalling pathway and conjunctival remodelling in vernal keratoconjunctivitis.
BACKGROUND
Vernal keratoconjunctivitis (VKC) is a chronic ocular allergic inflammation characterized by corneal complications and the formation of giant papillae. Sma- and Mad-related proteins (Smad) modulate extracellular matrix gene expression during wound healing, inflammation and tissue remodelling.


OBJECTIVE
To investigate the relationship between allergic inflammation and TGF-β/Smad signalling pathway, expression in VKC patients and in primary cultured conjunctival fibroblasts exposed to mediators found previously over-expressed in VKC.


METHODS
Smad-2, -3, -7, phospho-(p)Smads, TGF-β1 and -β2 were evaluated in the conjunctiva of normal subjects (CT) and VKC patients by immunohistochemistry. The expression of Smads, pro-collagen I (PIP), TGF-β1, -β2, mitogen-activated protein kinase (p38/MAPK), c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK1/2) were also determined in conjunctival fibroblast cultures exposed to histamine, IL-4, -13, TGF-β1, IFN-γ and TNF-α using immunostaining or RT-PCR.


RESULTS
Immunostaining for Smad-2, -3, pSmad-2, -3, TGF-β1, -β2 and PIP was significantly increased in VKC stroma compared with CT. In conjunctival fibroblast cultures, Smad-3 and PIP were stimulated by histamine, IL-4, -13 and TGF-β1 exposure, while PIP was reduced by IFN-γ, and TNF-α mRNA expression of Smad-3 was increased by histamine, while Smad-7 was reduced by IL-4. In addition, histamine, IL-4 and TNF-α increased JNK and ERK1/2 expression.


CONCLUSIONS
The TGF-β/Smad signalling pathway is over-expressed in VKC tissues and modulated in conjunctival fibroblasts by histamine, IL-4, TGF-β1 and TNF-α. These mechanisms may be involved in fibrillar collagen production, giant papillae formation and tissue remodelling typical of VKC and might provide new therapeutic targets for its treatment.
Leonardi
A
A
Ophthalmology Unit, Department of Neuroscience, University of Padua, Padua, Italy. andrea.leonardi@unipd.it
Di Stefano
A
A
Motterle
L
L
Zavan
B
B
Abatangelo
G
G
Brun
P
P
D000293:Adolescent; D002648:Child; D003228:Conjunctiva / Q000276:immunology*; D003233:Conjunctivitis, Allergic / Q000175:diagnosis / Q000235:genetics / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D018448:Models, Immunological; D012333:RNA, Messenger / Q000235:genetics / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology*; D051785:Smad Proteins / Q000235:genetics / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000276:immunology*
D012333:RNA, Messenger; D051785:Smad Proteins; D016212:Transforming Growth Factor beta