Abnormalities of stromal structure in the bullous keratopathy cornea identified by second harmonic generation imaging microscopy.
OBJECTIVE
To identify structural alterations in collagen lamellae and the transdifferentiation of keratocytes into myofibroblasts in the corneal stroma of bullous keratopathy (BK) patients and to examine the relation of such changes to the duration of stromal edema or the underlying cause of BK.


METHODS
Six normal human corneas and 16 BK corneas were subjected to second harmonic generation (SHG) imaging microscopy to allow three-dimensional (3-D) reconstruction of collagen lamellae. Expression of α-smooth muscle actin (αSMA) was examined by immunofluorescence analysis and conventional laser confocal microscopy.


RESULTS
Collagen lamellae were interwoven at the anterior stroma and uniformly aligned at the posterior stroma, whereas αSMA was not detected throughout the entire stroma of the normal cornea. Nine (56%) and 7 (44%) of the 16 BK corneas showed abnormal collagen structure at the anterior and posterior stroma, respectively. Expression of αSMA was detected in the anterior or posterior stroma of 7 (44%) and 6 (38%) of the 16 BK corneas, respectively. Disorganization of collagen lamellae and myofibroblastic transdifferentiation were detected only in corneas with a duration of stromal edema of at least 12 months. Corneas with BK as a result of birth injury showed abnormal collagen structure at the posterior stroma, whereas those with BK resulting from laser iridotomy did not.


CONCLUSIONS
Changes in the structure of the entire stroma were detected in BK corneas with a duration of stromal edema of at least 12 months, suggesting that such changes may be progressive. In addition, the underlying cause of BK may influence structural changes at the posterior stroma.
Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan. morishig@yamaguchi-u.ac.jp
Naoyuki
N
Morishige
Norihiro
N
Yamada
Xu
X
Zhang
Yukiko
Y
Morita
Naoyuki
N
Yamada
Kazuhiro
K
Kimura
Atsushi
A
Takahara
Koh-Hei
KH
Sonoda
D000199:Actins / Q000648:ultrastructure*; D000368:Aged; D000369:Aged, 80 and over; D054338:Cell Transdifferentiation / Q000502:physiology; D003094:Collagen / Q000648:ultrastructure; D003316:Corneal Diseases / Q000473:pathology*; D003319:Corneal Stroma / Q000002:abnormalities*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D015603:Keratinocytes / Q000166:cytology; D008297:Male; D008875:Middle Aged; D058628:Myofibroblasts / Q000166:cytology
C541116:ACTA2 protein, human; D000199:Actins; D003094:Collagen