Biomechanical Changes And Mechanism Of Long-pulse 1064nm Nd:YAG Laser Reshaping Of Rabbit Ear Cartilage

ObjectiveThere are a large number of children with ear deformities and cartilage deformation in clinic.Laser remodeling of cartilage has been proved to be effective in clinic,but its mechanism is still not clear.The purpose of this study is to screen the energy of long pulse width 1064nm Nd:YAG laser remodeling of rabbit ear cartilage,study its biomechanical changes and mechanism,and verify the related signal pathways and the changes of differential gene expression.The purpose of this study is to provide scientific and theoretical basis for the clinical application of laser remodeling of cartilage.Methods1.Six New Zealand rabbits were used in the laser energy screening experiment,with the left ear as the blank control group and the right ear as the observation group.Each rabbit in the observation group was irradiated with 50,60,70,80,90 and 100J/cm2 energy for histological observation,and the laser energy which could achieve stress relaxation and reduce the damage of chondrocytes and matrix was screened out.2.Three New Zealand rabbits were used in the RNA sequencing experiment in the auricular cartilage transcription group,with the left ear as the blank control group and the right ear as the observation group.After the observation group was irradiated with the previously screened 80J/cm2 laser energy,the rabbit ear cartilage of the two groups were immediately taken for RNA sequencing in the transcriptional group,and the related signal pathways and their differential genes were screened.3.Twenty-four New Zealand rabbits were randomly divided into 4 groups.Biomechanical test,histological observation,collagen content detection,local estrogen concentration detection,aromatase concentration detection and hyaluronic acid concentration detection were performed immediately,1 week,3 weeks and 6 weeks after 80J/cm2 laser irradiation.The expression of CREB3L2 was detected by Q-PCR,immunohistochemistry and Western blot,the biological characteristics at different time points were observed,and the related signal pathways and the changes of differential gene expression were verified.Results1.Under the irradiation of different energy laser,the histological observation results showed that 80J/cm2 could change the chondrocytes without vacuole deformation and coagulation necrosis,and the injury was suitable.2.Under the laser energy irradiation of the previously screened 80J/cm2,the transcriptome RNA sequencing results showed that the cAMP-PKA signal pathway may be activated and the expression of CREB3L2 may be up-regulated after laser irradiation.3.Under the laser energy irradiation of 80J/cm2,the biomechanical test results show that the peak values of tensile stress,compressive stress,bending stress and elastic modulus are significantly different from those of the normal control group(P<0.05),and the ability to resist tension and bending decreases and the ability to resist compression failure increases with the extension of time.The histological results showed that the laser radiation band appeared immediately after operation,and the overall morphology of chondrocytes on the radiation zone was elongated,showing fusiform cell-like changes,the matrix staining was deep,the refraction was obvious,the collagen was relatively increased,and the radiation band became shallower at 1 week.the cell size recovered,and the staining of the matrix around the radiation zone gradually deepened and the overall shape was elongated from 3 weeks to 6 weeks.The levels of estrogen,aromatase and hyaluronic acid in local rabbit ear cartilage increased gradually after laser irradiation.Immunohistochemistry showed that CREB3L2 was positive,Q-PCR and Western blot detection showed that the expression of CREB3L2 was up-regulated,and with the extension of time,the expression was more obvious.ConclusionAfter long pulse width 1064nmNd:YAG laser irradiation,the ability of rabbit ear cartilage to resist plastic deformation increases,while the ability to resist elastic deformation decreases,that is,the stress decreases,and the morphology changes more easily;This activate the cAMP-PKA signal pathway,up-regulate the expression of CREB3L2,cause chondrocyte rearrangement and proliferation,and lead to morphological changes of ear cartilage.