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[Study on enhanced leukocyte antigen-related tyrosine phosphatase in keratoconus].

OBJECTIVE
To study the enhanced expression of leukocyte antigen-related tyrosine phosphatase (LAR) in human keratoconus cornea.


METHODS
Corneal buttons of patients received keratoplasty in Eye Center of Beijing Tongren from December 2001 to March 2002 were collected. Total RNA was isolated from the buttons from keratoconus (15 eyes), normal cornea (7 eyes), bullous keratopathy (6 eyes), non-neovascular cornea scar (3 eyes) and corneal dystrophy (2 eyes). Polymerase chain reaction (RT-PCR) was performed in this group. The results were displayed by agarose gels electrophoresis. In another group of patients, the corneal buttons of patients received keratoplasty in Eye Center of Beijing Tongren from July 2002 to December 2002 were collected. Total protein was extracted from the buttons of keratoconus (6 eyes), normal cornea (3 eyes), bullous keratopathy (3 eyes), non-neovascular cornea scar (3 eyes) and corneal dystrophy (2 eyes). Western blot was performed in this group. The results were displayed by enhanced chemical illumination. Bands of LAR RNA and LAR protein from these two tests were analyzed quantitatively.


RESULTS
In RT-PCR study using the same amount of total RNA, high signal of LAR RNA was detected in RNA from the keratoconus, whereas low or no signal was detected in normal cornea and other diseases. Sequence analysis of the product of amplified LAR fragment from keratoconus showed deletion of exon 13. In Western blot study using the same amount of total protein, high signal of LAR was detected in keratoconus by the LAR antibodies, while low or no signal was detected in normal cornea and other diseases.


CONCLUSIONS
LAR mRNA and protein are enhanced in keratoconus, whereas there are low or no expression in normal cornea, bullous keratopathy, non-neovascular cornea scar and corneal dystrophy. Elevated LAR in keratoconus indicates that LAR plays an essential role in the occurrence of keratoconus. Deletion of exon 13 in keratoconus may play a potential role in the abnormal LAR function.