Effects Of Functional Site External Fixation On JAK/STAT Pathway-related Gene Expression After Achilles Tendon Injury In Rabbits

Background Tendon is an important part of musculoskeletal system.Its powerful mechanical properties enable it to transfer muscle contraction force to the skeleton to maintain posture or generate movement^[1].Among them,Achilles tendon is the largest and strongest tendon in human body.It is located in the back of the leg,connected to the calcaneus?calcaneus?,and connects the leg muscles to the feet.Tendons are composed of dense connective tissue,mainly composed of type I collagen fibers,which contain collagen fibers.Type I collagen fibers are usually ribbon-like with a circumference of 67 nanometers.In these tendons,collagen fibers are thicker and harder,usually forming transversely assembled collagen fibers in a plane zigzag shape,and the bending area acts as a flexible hinge.^[2]The degree of intramolecular and intermolecular crosslinking between collagen molecules makes the tendon have mechanical strength.^[3]Tendon injuries are common,accounting for almost one third of all musculoskeletal diseases.^[4]In addition,the repair process of tendon injury is slow,which usually leads to scar tissue and incomplete recovery.^[5]The recovery of normal structure and function of tendons has been one of the challenges in orthopaedics.Objective To verify the hypothesis that functional fixation of Achilles tendon promotes the synthesis of collagen I and III by regulating JAK/STAT signal transduction pathway.Methods 40 adult healthy male New Zealand white rabbits,weighing an average of 2-2.5 kg,were randomly divided into two groups,20 rabbits in each group.They were divided into group A?experimental group?and group B?control group?respectively.In group A,ankle joint functional position was fixed after Achilles tendon suture.Group B received ankle joint relaxation fixation after Achilles tendon surgery.Samples were collected on the 1st,3rd,5th,7th,14th and 28th day after operation.The expression of STAT 1,STAT3,collagen I and III genes in repaired tissues were detected by RT-PCR,and collagen I and III in repaired tissues were quantitatively detected by ELISA.Result At the 5th,7th,14th and 28th day after operation,the expression level of COL I gene in group A was significantly higher than that in group B?P<0.05?.COL III gene expression level in group A was significantly higher than that in group B at the 1st,5th and 28th day after operation?P<0.05?.At the first,third,fifth,seventh and twenty-eighth days after operation,the level of type I collagen in group A was significantly higher than that in group B?P<0.05?.At the 3rd,5th,7th and 14th day after operation,the level of collagen type III in group A was significantly higher than that in group B?P<0.05?.At the 3rd,5th,7th,14th and 28th day after operation,the expression level of STAT1 gene in group A was significantly higher than that in group B?P<0.05?.At all time points,the expression level of STAT3 gene in group A was significantly higher than that in group B?P<0.05?.Conclusion The results showed that:1)The expression levels of collagen I and III genes and JAK/STAT pathway related genes?COL I and COL III?in functional plaster external fixation group after experimental Achilles tendon injury in rabbits were higher than those in relaxed ankle plaster external fixation group.2)Functional site fixation may promote tendon healing by JAK/STAT pathway related gene expression and COL I,COL III protein gene expression.