Experimental Study On The Effect Of Imiquimod On Deep Partial Thickness Burn Wound Healing In Wistar Rats

ObjectiveBy comparing the representation of deep partial thickness burn wound after using imiquimod, observe the changes in wound healing time and collagen deposition. On this basis, discuss whether imiquimod can play an effective role in prevention of scar conformation and contracture.MethodsPreparation of experimental model, fifty adult Wistar rats, male, were used in this study. Control method using the same body, each rat had eight 10mm×10mm squares; four were evenly outlined on each side and along the longest axis of the vertebral column using a prepared template positioned between the anterior and posterior limbs.Wounds of the right side were the experimental group, wounds of the left side were the control group.The wounds of experimental group were randomly allocated for treatment with cotton gauze soaked in 5% IMQ cream overnight. The wounds of control group were treated with Vaseline pledget. Treatment started the day after burn infliction and repeated on PBD 3,PBD 5,PBD 8,PBD 10 PBD12,PBD 15,PBD 17,PBD 19,PBD 22,PBD 24,PBD 26. On five occasions (PBD 4,7,14,21and 28), ten animals were anesthetized and executed separately. Tissue was then collected from the dorsum with a surgical blade. Observed whether the wounds showed infection. H-E stained sections were examined by light microscopy, to observe the inflammation and healing of the wounds; Under polarized-light microscope and photographed, Picric acid-Sirius red stained were examined type-Ⅰand type-Ⅲcollagen content; By chemical assay, examined the change of HOP content; Using SPSS 11.5 statistical software, Data was examined with Paired-Sample T test, and P<0.05 for the difference was statistically significant.Results1.Wound healing time and rate of scar shrinkageThe time of IMQ group was 25.2±1.7d,while the time of Vaseline pledget group was 24.4±1.3.P>0.05,there was no significant;Rate of scar shrinkage:The rate of IMQ group was(46.7±4.82)%, while the rate of control group was (70.4±5.35)%.P<0.05,there was a significant difference. So, IMQ could lighten scar contraction;2.H-E stainedOn PBD 4, there was no significant between experimental group and control group;on PBD 7,14 and 21,the inflammation of experimental was stronger than control group, but fibroblasts and collagen fibers were less than control group, P<0.05,there was a significant difference; on PBD 28,the wounds of both groups recovered with epithelial cells and were complete and evenly, but fibrosis of control group was more serious than experimental group;3.Picric acid-Sirius red stained and analysis of type-Ⅰ/type-Ⅲcollagen contentType-Ⅰcollagen deposition had increased in control group and decreased in experimental group. Type-Ⅲcollagen deposition was not found significant difference in both groups.The type-Ⅰ/type-Ⅲcollagen ratio was different between two groups.Before PBD 7,the rate in control group was increased. Subsequently, it was decreased; while, in experimental group, the rate was decreased since PBD 4;4.Hydroxproline(HOP) detectionDuring the process of the wound healing, HOP was increased in both two groups. Since PBD 21,it began to decrease. But in control group, the growth was larger than experimental group.And in same point it had a significant difference, P<0.05.ConclusionDuring the healing process, IMQ has no effect on wound healing time, but it can significantly improve scar shrinkage. Fibroblasts and collagen fibers in IMQ treatment group were less than control group. Type-Ⅰcollagen deposition in IMQ treatment group was decreased and total collagen was less than control group.So, IMQ could inhibit the growth of fibroblasts, lighten scar contraction, decrease collagen deposition, especially type-Ⅰcollagen.