Loss of osteopontin perturbs the epithelial-mesenchymal transition in an injured mouse lens epithelium.
We previously reported that osteopontin (OPN), a matrix structural glycophosphoprotein, is upregulated in the injured mouse lens prior to the epithelial-mesenchymal transition (EMT). Here, we investigated the role of this protein in EMT of the lens epithelium during wound healing. The crystalline lens was injured by needle puncture in OPN-null (KO, n=40) and wild-type (WT, n=40) mice. The animals were killed at day 1, 2, 5, and 10 postinjury. Immunohistochemistry was employed to detect alpha-smooth muscle action (alphaSMA), a marker of EMT, collagen type I, transforming growth factor beta1 (TGFbeta1), TGFbeta2, and phospho-Smad2/3. Cell proliferation was assayed by examining uptake of bromodeoxyuridine (BrdU). The results showed that injury-induced EMT of mouse lens epithelium, as evaluated by histology, expression pattern of alphaSMA and collagen I, was altered in the absence of OPN with reduced phospho-Smad2/3 signaling. Upregulation of TGFbeta1 and TGFbeta2 in the epithelium was also inhibited. Cell proliferation was more active in KO mice as compared with WT mice at day 1 and 2, but not at day 5 and 10. An in vitro experiment shows OPN facilitates cell adhesion of lens epithelial cell line. OPN is required for activation of Smad2/3 signal in an injured lens epithelium and lens cell EMT.
Saika
Shizuya
S
Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan. shizuya@wakayama-med.ac.jp
Shirai
Kumi
K
Yamanaka
Osamu
O
Miyazaki
Ken-Ichi
K
Okada
Yuka
Y
Kitano
Ai
A
Flanders
Kathleen C
KC
Kon
Shigeyuki
S
Uede
Toshimitsu
T
Kao
Winston Whei-Yang
WW
Rittling
Susan R
SR
Denhardt
David T
DT
Ohnishi
Yoshitaka
Y
D000199:Actins / Q000378:metabolism; D000818:Animals; D001973:Bromodeoxyuridine; D002448:Cell Adhesion / Q000502:physiology; D024042:Collagen Type I / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D007150:Immunohistochemistry; D007908:Lens, Crystalline / Q000166:cytology* / Q000293:injuries* / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology*; D051379:Mice; D018345:Mice, Knockout; D053495:Osteopontin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051899:Smad2 Protein / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D014945:Wound Healing / Q000502:physiology*
D000199:Actins; D024042:Collagen Type I; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D053773:Transforming Growth Factor beta1; D053495:Osteopontin; D001973:Bromodeoxyuridine