Effect Of MMP-8 And MMP-9 On The Opacity Degree Of Cornea

ObjectiveTo investigate the effects of MMP-8 and MMP-9 on the opacity degree of cornea,and to compare the effects of MMP-8 and MMP-9 on corneal matrix collagen.MethodsEight C57BL/6J mice with normal cornea were selected and used for in vitro experiment.Mice were killed after intraperitoneal anesthesia.Their corneas were randomly divided into 4 groups,MMP-8 group and MMP-9 group as experimental groups,Assay Buffer group as negative control group,and normal saline as blank control group.The 16 corneas were respectively put into the 96 orifice plate containing 100 ?L 20 ng/?L rmMMP-8,20 ng/?L rmMMP-9,Assay Buffer and normal saline.Hydroxyproline concentrations were measured after 24 hours' incubation at 36.5 centigrade degree.30 C57BL/6J mice with normal cornea were selected and used for in vivo experiment.They were randomly divided into 3 groups,MMP-8 group and MMP-9 group as experimental groups,and normal saline as blank control group.They were respectively given injection of about 10 ?L 20 ng/?L MMP-8,20 ng/?L MMP-9 and normal saline into coneal stroma.At 0,4,8,12,20 and 24 hours they were examined under slit lamp for the opacity score,and cornea stroma was scanned by second harmonic generation.At 8 hours and 24 hours after cornea stroma injection,mice were sacrificed for corneal hydroxyproline concentration determination.ResultsDuring in vitro experiment,corneal hydroxyproline concentration of experimental group was significantly lower than that of negative control group(F = 451.492,P = 0.000)and blank control group(F = 252.403,P = 0.000).Corneal hydroxyproline concentration of MMP-9 group was significantly lower than that of MMP-8 group(F = 55.184,P = 0.002).During in vivo experiment,at 0h,that is,before the corneal stroma injection,corneal transparency between the experimental groups and the control groups had no significant difference(?2 = 0.000,P = 1.000).At 0,4,8,12,20 and 24 hours,corneal opacity degree of experimental groups was significantly higher than control group(P < 0.05).At 0,4,8,12,20 and 24 hours,there was no significant difference in corneal opacity between MMP-8 group and MMP-9 group(P > 0.05).At 0,4,8,12,20 and 24 hours,corneal stromal signal intensity of experimental groups was significantly lower than that of control group(P < 0.05).The results had no significant difference between MMP-8 group and MMP-9 group(P > 0.05).At 8 hours,part of the mice corneas were analysed for corneal Hyp concentration,and corneal Hyp concentration was significantly lower in experimental groups than the control group(F = 17.877,P < 0.001).Comparing MMP-8 group with MMP-9 group,the results had no significant difference(P > 0.05).At 24 hours all else mice cornea were analysed for corneal Hyp concentration and corneal Hyp concentration was significantly lower in experimental groups than the control group(F = 41.400,P < 0.001).Comparing MMP-8 group with MMP-9 group,the results had no significant difference(P > 0.05).Correlation analysis between SHG corneal stromal signal intensity of MMP-8 group and corneal opacity clinical score presented negatively correlated(rs =-0.511,P < 0.001).Correlation analysis between SHG corneal stromal signal intensity of MMP-9 group and corneal opacity clinical score presented negatively correlated(rs =-0.613,P < 0.001).ConclusionsMMP-8 and MMP-9 can degrade collagen in corneal stroma,resulting in abnormal alinement of corneal stroma collagen fiber,and finally opacity;MMP-9 had stronger ability to degrade collagen than MMP-8 during in vitro experiment at the same mass concentration,while the ability of MMP-9 and MMP-8 to degrade type ?collagen was not significantly different under the condition of corneal stroma injection at the same mass concentration.