ABSTRACT
Background Corneal walleye formation is a result of excessive corneal wound healing.Controlling the corneal trauma or excessive healing reaction after operation of penetrating corneal trauma is a focus in the study of corneal wound healing.Objective This study was to investigate the changes of corneal strength and the expression of keratocan,a marker of corneal stroma,after corneal penetrating injury operation,and to determine the optimal removal time of corneal suture.Methods Full-thickness incisions of 5 mm along the vertical diameter were done at the central cornea on 80 eyes of 80 six-month-old New Zealand rabbits in this study.Then the incisions were interruptedly sutured with 10-0 nylon thread to establish the corneal wound healing models.Each 4 rabbits were sacrificed in 1 week,2,3,4,5,6,7,8 weeks after operation,respectively,and the central corneal stripes were prepared with the size of 7 mm×5 mm.The mean maximal strength of the corneal bands was measured by uniaxial tensile test with electroforce3220-AT biomachanics machine.Then,each 6 whole corneas were obtained at the above time points,and the dynamic changes of keratocan mRNA expression in the specimens were detected by reverse trancription PCR (RT-PCR).The care and use of the animals followed the rules of ARVO.Results The mean maximal strength of corneal stripes was 0,(1.007 ± 0.041),(1.991 ± 0.034),(2.512 ± 0.030),(3.630 ± 0.049) and (4.935 ± 0.004)M Pa in 1 week,2,3,4,5,6 weeks after modeling,and the corneal strength values from 3 weeks through 6 weeks were significantly enhanced in comparison with the value at the adjacent before timepoint (q =6.35,7.54,8.21,5.86,all at P＜0.01).The relative expression levels (absorbance) of keratocan mRNA in the corneas were 0.869±0.015,0.779 ± 0.065,0.621 ± 0.027,0.460 ± 0.018,0.393 ± 0.057 and 0.255 ± 0.045 in 1 week,2,3,4,5,6 weeks after operation,and each value was lower than that of the adjacent before timepoint (q =5.24,5.61,7.49,4.75,5.47,all at P＜0.01).The intensity of corneal stripes and the expression levels of keratocan mRNA in the corneas were stable in 7 weeks and 8 weeks after operation.Conclusions The dynamic change of corneal strength during the repair of penetrating corneal injury is associated with the down-regulation of keratocan in cornea.Rabbit cornea reaches a maximal strength capacity in 6 weeks after penetrating injury,therefore,it is the optimal time to remove suture.