Smad7 suppresses the inhibitory effect of TGF-beta2 on corneal endothelial cell proliferation and accelerates corneal endothelial wound closure in vitro.
OBJECTIVE
The inhibitory activity of transforming growth factor-beta2 (TGF-beta2) on corneal endothelial cell proliferation is thought to be a cause of the limited regenerative capacity of corneal endothelial cells that may be related to impaired corneal transparency when many corneal endothelial cells are lost due to various stresses. We determined whether Smad7, an intracellular antagonist of TGF-beta signaling, regulated the inhibitory activity of TGF-beta2 or aqueous humor on corneal endothelial cell proliferation.


METHODS
The effect of Smad7 on TGF-beta2- or aqueous humor-mediated inhibition of corneal endothelial cell proliferation was evaluated using thymidine uptake assay with cultured rabbit corneal endothelial cells infected with adenovirus carrying Smad7. Expression of Smad or cell cycle-related proteins was detected by immunoblotting. In addition, a small scrape wound was made across a monolayer of Smad7-expressing cultured rabbit corneal endothelial cells to examine the effect of Smad7 on the wound-healing process in vitro.


RESULTS
Overexpression of Smad7 abolished the inhibitory effect of TGF-beta2 or aqueous humor on the proliferation of cultured rabbit corneal endothelial cells associated with the inhibition of phosphorylation of Smad2 and downregulation of p27kip1. Smad7-overexpressing cultured rabbit corneal endothelial cells exhibited shorter wound closure time in the presence of aqueous humor than LacZ-expressing cells.


CONCLUSIONS
Overexpression of Smad7 suppressed the inhibitory effect of TGF-beta2 or aqueous humor on corneal endothelial cell proliferation and accelerated corneal endothelial wound closure in vitro. Modification of Smad7 expression in corneal endothelial cells may thus have applicability in the treatment of wounded corneal endothelium.
Funaki
Toshinari
T
Department of Ophthalmology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, USA.
Nakao
Atsuhito
A
Ebihara
Nobuyuki
N
Setoguchi
Yasuhiro
Y
Fukuchi
Yoshinosuke
Y
Okumura
Ko
K
Ra
Chisei
C
Ogawa
Hideoki
H
Kanai
Atsushi
A
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001082:Aqueous Humor / Q000502:physiology; D015153:Blotting, Western; D002455:Cell Division; D002478:Cells, Cultured; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004728:Endothelium, Corneal / Q000166:cytology / Q000378:metabolism*; D015870:Gene Expression; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D008297:Male; D010766:Phosphorylation; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D051906:Smad7 Protein; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053781:Transforming Growth Factor beta2; D014945:Wound Healing / Q000502:physiology*
D004268:DNA-Binding Proteins; D051906:Smad7 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053781:Transforming Growth Factor beta2