Osteopontin: a component of matrix in capsular opacification and subcapsular cataract.
OBJECTIVE
To examine whether tissues of human capsular opacification and subcapsular cataract contain osteopontin, an adhesive matrix protein, and whether mouse lens epithelium expresses osteopontin after injury.


METHODS
An immunohistochemical examination was conducted to determine whether matrices in human postoperative capsular specimens and anterior subcapsular cataract contain osteopontin. The spatial and temporal protein expression patterns of osteopontin were then determined in epithelium of a healing mouse lens after a capsular incision.


RESULTS
Human lens epithelial cells in the specimens extracted at the time of vitrectomy 10 days after cataract surgery and also after longer healing intervals were labeled with an anti-osteopontin antibody, whereas uninjured lens epithelium was not. In the later healing phase, matrix of capsular opacification was positive for osteopontin. Lens cells amid anterior subcapsular cataract tissue were also positive. Osteopontin was detected in the cell surface and membrane and the cytoplasm of lens cells, as well as in the matrix. Unlike normal uninjured specimens, anterior lens capsule of some of the healing postoperative specimens and anterior subcapsular cataract specimens also faintly or weakly stained for osteopontin. Mouse lens epithelium started to express osteopontin protein at 8 hours after injury, before the cells changed their shape from epithelial cell type to fibroblast type. Expression of osteopontin lasted during the healing interval, even after the cells transformed into fibroblast-like cells.


CONCLUSIONS
Extracellular matrix in human postoperative capsular opacification and anterior subcapsular cataract contains osteopontin. Epithelial cells of a mouse lens also ectopically express osteopontin in response to capsular injury.
Saika
Shizuya
S
Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan. shizuya@wakayama-med.ac.jp
Miyamoto
Takeshi
T
Ishida
Iku
I
Ohnishi
Yoshitaka
Y
Ooshima
Akira
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000918:Antibody Specificity; D015153:Blotting, Western; D002386:Cataract / Q000378:metabolism* / Q000473:pathology; D002387:Cataract Extraction; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007903:Lens Capsule, Crystalline / Q000378:metabolism* / Q000473:pathology; D007908:Lens, Crystalline / Q000166:cytology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D053495:Osteopontin; D012795:Sialoglycoproteins / Q000378:metabolism*; D014821:Vitrectomy; D014945:Wound Healing
C506895:SPP1 protein, human; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D053495:Osteopontin