Repair The Ruptured Annular Fibrosus By Using TypeⅠ Collagen Combined With Citric Acid,EDC And NHS: An In Vivo Study

ObjectivesThe goal of our study was to evaluate the ability of Citric Acid-EDC/NHS collagen gel to repair a needle-puncture AF defect in the rat-tail spine.Specifically,we wanted to test whether injected collagen gel can prevent nuclear tissue extrusion and consequent IVD degeneration,as determined by histological and radiological outcomes.In addition,citric acid,a typical substance of the tricarboxylic acid(TCA)cycle,was added indifferent concentrations.In this study,the rat-tail model was used to screen these various compositions of collagen gels.MethodsType I collagen was extracted from rat-tail tendon.Citric acid(CA),1-Ethyl-3-(3-d imethylaminopropyl)carbodiimide(EDC)and N-hydroxysuccinimide(NHS)is the crosslinked reagent with collagen.Then the four solutions were mixed indifferent mass ratio to generate collagen gel.We used 48 adult SD rats for this study and they were divided into 5 groups.The first group of 8 was control.The second group of10 was punctured and injected with Citric Acid-EDC/NHS collagen gel(CA6).The third group of 10 was punctured and injected with Citric Acid-EDC/NHS collagen gel(CA3).The fourth group of 10 was punctured and injected with EDC/NHS collagen gel(CA0).The fifth group of 10 animals was punctured and left untreated.X-ray image and Magnetic resonance image(MRI)image was obtained preoperatively and at 1,2,and 4 weeks after puncture.At each time point,%DHI(Disc Height Index),voxels count and Modified Magnetic Resonance Imaging Pfirrmann Grading were collected and analyzed.All animals were killed at 4 weeks and used to study the morphology.ResultsThe discs in the Citric Acid-EDC/NHS collagen gel group(CA6)showed only a slight degeneration when compared with healthy discs,and the results of %DHI,voxels count,Pfirrmann Grading and morphology in the Citric Acid-EDC/NHS collagen gel(CA6)group displayed a less-degeneration tendency compared with other 3 punctured groups at 4 weeks.The annular fibrosus was partially repaired by collagen gel that bridged the defect.ConclusionsThe needle-punctured rat-tail has been shown to be a suitable in vivo model for studying biomaterials for annular repair.Citric Acid-EDC/NHS collagen gel is capable of repairing annular defects which are induced by needle puncture,and the result may be closely related with the dose of citric acid.