GELATINASE CONCENTRATION IN TEARS OF CORNEAL-GRAFTED PATIENTS

Purpose. Gelatinolytic enzymes, which degrade type IV basement membran e collagen, have been shown to be expressed by corneal cells, either c onstitutively (gelatinase A or MMP-2) or after induction (gelatinase B or MMP-9. Our aim was to determine whether an enhanced MMP-9 and even tually MMP-2 concentration in tears could be evidenced in the case of corneal-graft failure. Methods. The amount of MMP-2 and MMP-9 gelatino lytic enzymes was measured by quantitative zymography in tears of twen ty-one controls (84 samplings) and in tears of twenty-three corneal-gr afted patients in a one-year post-graft follow-up study. Results. The mean MMP-2, values in controls were of 8.4 (+/-7.3) pg/10 mu g protein and the mean MMP-9 values in controls were of 73 (+/-76) pg/10 mu g p rotein. No active gelatinase form was detected in any of controls, but in all cases of corneal graft failure, the active forms of both enzym es were present, and enzyme concentrations were higher than control va lues. All patients had significantly higher MMP-9 values than controls at each sampling time (p < 0.0001). The ''corneal-graft failure'' pat ient group had statistically significant higher MMP-9 concentrations i n tears than the ''successful-graft'' patient group at one month (p = 0.0312), four months (p = 0.0158) and one year (p < 0.01) after the gr aft. The presence of active MMP-9 was highly significant of graft fail ure four months and one year after the graft (p < 0.0001). In contrast , MMP-2 increase was delayed, with significantly higher MMP-2 values t han controls in all patients at four months (p = 0.0231) and one year (p = 0.0001) after the graft, but MMP-2 values could not discriminate between patient groups. Conclusions. In our study, all cases of graft failure showed abnormally high levels of the active forms of metallopr oteinase enzymes, and these values far exceeded the maximum control co ncentration. MMP-9 measurements in tears made between one and four mon ths after corneal transplantation, and while local corticotherapy is s teadily established, should help in predicting corneal graft rejection .