Effect Of Timolol Maleate Eye Drops On Hypertrophic Scar Of Rabbit Ear

Objective: To investigate the effect of timolol maleate eye drops on hypertrophic scar of rabbit ear by observing the changes of morphological structure and histopathology of hypertrophic scar of rabbit ear and the expression of BGN and DCN in scar tissue,so as to provide a new scheme for the treatment and prevention of pathological scar.Methods: Twenty Japanese white rabbits with large ears,weighing 2.5-3.0kg,male and female,with healthy ears on both sides and no deformity were selected.The rabbit ear hypertrophic scar model was established on the ventral side of both ears and along the long axis to avoid the location of large blood vessels.Each rabbit ear made four round wounds with a diameter of about 1cm,with an interval of about 2.0cm,a total of 160 wounds.They were randomly divided into 4 groups: a model group(blank control group),B saline group(negative control group),C triamcinolone acetonide group(positive control group),D timolol maleate eye drops group(experimental group),with 40 scar model wounds in each group.Iodophor cotton balls were routinely used for disinfection after operation,and escharectomy was given one week to form secondary trauma.The drug was given from 21 days after operation when the wound was completely epithelized,and no treatment was given in model group A;The remaining three groups B,C and D were given 1ml of corresponding drugs twice a day in the morning and evening.According to the Vancouver Scar Scale,the changes of scar tissue were observed and recorded every day,and scar samples were collected 21 and 42 days after treatment.After hematoxylin eosin staining(he),the pathological changes of rabbit ear scar tissue were observed under optical microscope and the scar hyperplasia index was measured;The expressions of BGN and DCN in rabbit ear scar were detected by immunohistochemistry.In this experiment,Graphpad prism 8.0 was used for data analysis.In this paper,measurement data were expressed as rate or percentage,and statistical results were expressed as mean ± standard deviation(SD).Differences between groups were analyzed using one-way analysis of variance(One-Way Anova)or t-test,and p<0.05 means the difference is statistically significant.Results:1.One week after the operation,all wounds formed a dry and hard white crust at the bottom,and peeled off the crust;two weeks after the operation,the wound began to heal to the center of the wound and became a crust,and the crust gradually fell off with time.;Three weeks after the operation,the wounds were completely covered by epithelial tissue,and the epithelization was completed.On the naked eye,all the scars were dark and purple;hyperplastic scar tissue with obvious prominence and hard texture could be palpated;the appearance and shape of the scars were consistent with the wound surface and were round,and the hyperplasia boundaries were all within the scope of the wound surface.On the 21 st day after the operation,the patients were divided into groups and treated between different groups.Using the Vancouver scar scale(VSS)as the measurement,compared with the model group,there was no statistical difference in the VSS score between the groups before treatment;after 3 weeks of treatment and 6 weeks after treatment,the positive control group and the experimental group The VSS scores of all groups decreased significantly(p<0.01).For the positive control group and the experimental group,the VSS score after 6 weeks of treatment was significantly lower than that after 3 weeks of treatment(p<0.01).2.Dermoscopy manifestations: When the wounds were epithelialized to form scars 3weeks after operation,all scars under dermoscopy appeared purple-red.After 3 weeks of drug treatment,under dermoscopy,the scars in groups A and B were dark red,while those in group C were dark red.The color of the scar was light red,and the color of the scar in group D was between red and light red;after 6 weeks of drug treatment,the color of the scar in group A and B was bright red,and the color of the scar in group C and D was similar to the color of the surrounding normal skin tissue,which is flesh pink.3.HE staining and hypertrophic index(Hypertrophic Index,HI): after HE staining of all scar tissue specimens,under the same administration time(3 weeks/6 weeks),compared with C and D under light microscope.group: The dermis of the scar tissue specimens in groups A and B was obviously thickened,and there were many fibroblasts/myofibroblasts deposited.The collagen fibers were dense and disorderly arranged.New blood vessels and inflammatory cells;the microscopic manifestations of C and D groups were opposite.However,no skin appendages were found in the 4groups.With the difference of medication time,compared between the same groups,when the medication was used for 6 weeks compared to when the medication was used for 3 weeks: the microscopic view of the A and B groups was significantly worsened,while the C and D groups were more relieved than before.According to the HI measurement method under the light microscope,the scar hyperplasia index(HI)between each group was measured,and compared with the model group,there was no significant difference between the HI score of the negative control group and the model group after 3 weeks of treatment and 6 weeks of treatment.difference(p>0.05),while the HI scores of the positive control group and the experimental group decreased significantly(p<0.01).For the positive control group and the experimental group,the HI score after 6 weeks of treatment was significantly lower than that after 3 weeks of treatment(p<0.01),while the HI score in the model group and the negative control group was significantly increased.It shows that the two drugs have better therapeutic effect on scar,and the effect of inhibiting scar hyperplasia is better with the increase of treatment time.4.Determination of BGN: The BGN in the scar tissue was stained by immunohistochemistry and analyzed under a microscope at 200 magnifications.The expression of BGN in normal skin was about 10.39%,and it increased after modeling.compared with the model group,the expression of BGN in the negative control group did not change significantly after 3 or 6 weeks of treatment,while the BGN content in the positive control group and the experimental group was significantly decreased after 3 and 6 weeks of treatment(p<0.01).In the positive control group and the experimental group,there was no significant change in the expression of BGN after 6weeks of treatment and 3 weeks after treatment.5.DCN determination: The DCN in the scar tissue was stained by immunohistochemistry and analyzed under a microscope at 200 magnifications.The DCN expression in normal skin was about 34.65%.After modeling,the DCN expression decreased.compared with the model group,the expression of DCN in the negative control group did not change significantly,while the DCN content in the positive control group and the experimental group increased significantly after 3 and 6weeks of treatment(p<0.01).In the positive control group,the expression of DCN after 6 weeks of treatment was significantly higher than that after 3 weeks of treatment(p<0.01).Conclusion:1.At present,the model of hypertrophic scar using rabbit ear has been stable and feasible,which provides a reliable foundation for future researches on hypertrophic scar;2.It is found through experiments that TTM can effectively reduce scar thickness,dilute scar color,and soften the original hard texture of scar;3.TTM can reduce scar hyperplasia by inhibiting excessive proliferation of fibroblasts and excessive deposition of collagen fibers in scar tissue;And with the prolongation of medication time,scar morphology has different degrees of change.