A Biomechanic Study On Healing Reaction Of Penetrating Injury In Rabbit Cornea

The cornea is located in front of the eye and is the most transparentorganization of the eye. It accounts for70%in the total diopter of the eyeball.The cornea directly contacts with the outside world while the cornea isvulnerable. Studies have shown that the corneal rupture is33.28%in theeyeball rupture. If it can not be handled correctly will cause seriousconsequences, such as blindness. Therefore, the study of corneal penetratinginjury is very important for the treatment of blinding diseases.Studies have shown that the cornea is a anisotropic biological material,and the nature of the collagen fibers within the cornea is also anisotropic.This internal structure can affect the carrying capacity of the corneal woundhealing and corneal shape. Corneal stromal cells or fibroblasts transfermmyofibroblasts in corneal wound healing.These cells promote corneal woundhealing, meanwhile,cell characteristics will follow changes and becomesopaque, and thus the corneal scar is formated and visual acuity is affected.At present, corneal penetrating injury is sutured in10-0nylon suturemethod, and corneal sutures are removed after45-90days. As we all know, ifcorneal sutures are removed advance, it may result in corneal wound healing isnot complete. And then, it will reduce the toughness of the cornea. If cornealsutures are removed too late, it will not only lead to pain for patients becauseof the long-standing corneal suture but also affect visual acuity because ofcornea scar which stimulation of corneal sutures bring. So, it is very necessaryto discuss corneal suture removal time. However, the correlation has not beenreported in the studies.This study aimed to explore the best of corneal stitches time to at thesame time enhance the toughness of the cornea and to reduce scar formationand corneal astigmatism. The first part biomechanical changes of rabbit cornea after Penetratinginjury operationObjective: to study biomechanical changes after corneal penetratinginjury operation at different time points.Method:40rabbits are produced corneal suture model of penetratinginjury and divided into eight groups randomly (n=5). After1week,2weeks,3weeks,4weeks,5weeks,6weeks,7weeks,8weeks,to take the5pieces ofcornea wound and to do tensile failure experiments by the BOSEelectroforce3220-AT biomechanical machine.Results: With the prolongation of time, the tension of rabbit corneaincreases and reaches a maximum at6weeks, then it is gradually stable after6weeks. There were significant statistical difference from1to6.6weeks and7weeks showed no significant statistical difference.Conclusion: Rabbit cornea has reached a larger tensile capacity afterpenetrating injury after6weeks. It is the best time to remove the suture.The second part Changes in cornea markers after Penetrating injury ofrabbit corneaPurpose：To study changes of keratocan, vimentin, CD90and α-SMAmarker proteins after penetrating injury of rabbit cornea at different timepoints. Designed to observe the corneal scar formation when the cornea up tothe maximum tension and provide a reference for the corneal suture removaltime.Method:32rabbits are produced corneal penetrating injury model and aredivided into eight groups randomly, each group4. To take whole cornea atevery time point respectively from1week to8weeks. To detect geneexpression of keratocan, vimentin, CD90, α-SMA using RT-PCR method inthe corneal at every time point. Then, to determin vimentin, α-SMA proteincontents in cornea by immunohistochemistry.Results: RT-PCR results showed that keratocan in corneal stromal cellmarkers decreased gradually with changes of time in the wound healingprocess after cornea penetrating injury operation. There was the most significant decline at first6weeks, gradually stable after6weeks.Simultaneously,fibroblasts or myofibroblasts marker CD90and α-SMA hadexpression, and the expression gradually increased with time. There was themost significant increased at first6weeks, gradually stable after6weeks.Above all the proteins,there were significant statistical difference from1to6weeks(P<0.01).6weeks to8weeks showed that there were no significantstatistical difference (P>0.05).With the extension of time after surgery,vimentin expression gradually increased. There were significant statisticaldifference from1to6weeks(P<0.01).6weeks and7weeks showed nosignificant statistical difference (P>0.05).Immunohistochemical data showedthat: as the extension of time, α-SMA with myofibroblast marker expressiongradually increased and had the most significant changes at6weeks. Therewere significant statistical difference from1to6weeks(P<0.01).Vimentin is amarker of intermediate filaments cells. Vimentin expression increased firstlyand then declined finally, and had the most significant changes at3weeks.Conclusion: Corneal stromal cells gradually reduced and converted intofibroblasts or moyfibroblasts in cornea wound healing after penetrating injuryof rabbit cornea. The convertion of cornea stromal cells achieve the least stateat6weeks.