Increased expression of osteonectin/SPARC mRNA and protein in age-related human cataracts and spatial expression in the normal human lens.
OBJECTIVE
We have previously reported increased levels of Osteonectin/SPARC transcript in age-related cataractous compared to normal human lenses. The purpose of the present study was to evaluate the corresponding levels of osteonectin/SPARC protein in age-related cataractous relative to normal lenses and to evaluate the levels of osteonectin/SPARC transcript in specific types of age-related human cataracts. The spatial expression of osteonectin/SPARC was also evaluated in normal human lenses.


METHODS
Specific types of age-related cataracts were collected and graded. Normal human lenses were microdissected into epithelia and fibers. Osteonectin/SPARC protein levels were monitored by Western immunoblotting, and transcript levels were evaluated by reverse transcriptase polymerase chain reaction (RT-PCR). Osteonectin/SPARC expression patterns were examined by RT-PCR and by immunostaining.


RESULTS
Higher levels of osteonectin/SPARC protein were detected in age-related cataractous relative to normal human lenses. Increased levels of osteonectin/SPARC transcript were also detected in posterior-subcapsular and nuclear cataractous lenses relative to normal lenses. Osteonectin/SPARC transcripts were detected in the lens epithelium but not fibers. Osteonectin/SPARC protein levels were highest in the peripheral lens epithelium.


CONCLUSIONS
Consistent with our previous studies on osteonectin/SPARC mRNA levels, osteonectin/SPARC protein levels were also elevated in cataractous compared to normal human lenses. Increased levels of osteonectin/SPARC mRNA were also found in nuclear and posterior-subcapsular cataracts relative to normal lenses. Osteonectin/SPARC expression is confined to the lens epithelium, and osteonectin/SPARC levels are highest in the peripheral lens epithelium.
Kantorow
M
M
Department of Biology, West Virginia University, Morgantown, WV 26505, USA. mkantoro@wvu.edu
Huang
Q
Q
Yang
X J
XJ
Sage
E H
EH
Magabo
K S
KS
Miller
K M
KM
Horwitz
J
J
D000293:Adolescent; D000368:Aged; D000375:Aging / Q000473:pathology*; D015153:Blotting, Western; D002386:Cataract / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007908:Lens, Crystalline / Q000378:metabolism*; D008875:Middle Aged; D015676:Osteonectin / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D015676:Osteonectin; D012333:RNA, Messenger