Study On The Effect Of Lithium-Based Composite Scaffold On The Repair Of Chronic Rotator Cuff Tear

Purpose:The repair of chronic rotator cuff injury mainly depends on surgery to strengthen the biomechanical connection between tendon and bone.There were many studies aiming to promote tendon bone healing after rotator cuff repair.However,chronic rotator cuff injury is often accompanied by fat infiltration,which leads to an increase in the rate of postoperative re-tear.At present,few studies have taken into account this aspect,let alone overcome the challenges of bone healing and fat infiltration simultaneously.The purpose of this project is to use a single biomaterial to solve both tendon-bone healing and fat infiltration problems at the same time.Methods:1.The Li~+@MSNs/PEUU composite system was established through electrospinning technology.Simple PEUU scaffold and Li~+/PEUU scaffold were set as the control group.The physical and chemical properties of the scaffold were tested in vitro.In addition,osteogenic induction test and adipogenic induction test were carried out in vitro to verify its effect of promoting osteogenesis and inhibiting adipogenesis.2.The rat model of chronic rotator cuff injury was established and strengthened on the basis of surgical repair with electrospun scaffolds.Control groups were set as:(1)simple surgical repair group,(2)surgery with PEUU scaffold group and(3)surgical with Li~+/PEUU scaffold group.The experimental group was surgical repair with Li~+@MSNs/PEUU scaffold group.The specimens were sacrificed at 2,4 and 8 weeks after operation.histological analysis,mechanical examination and micro-CT detection were performed to analyze the experimental results.Results:1.The Li~+@MSNs/PEUU composite electrospun membrane system was successfully established.The cowpea-like structure can be seen by TEM.This system has a good sustained release effect of lithium ion.The composite scaffold can promote osteogenic induction but inhibit adipogenic differentiation,and there is a significant difference in cell staining after induction.The results of RT-q PCR and Western blot showed that osteogenesis was promoted and adipogenic differentiation was inhibited.2.The rat model of fat infiltrating rotator cuff injury was successfully established and repaired.At 8 weeks,the oil red staining area of Li~+@MSNs/PEUU group was the smallest,while Sirius red,micro-CT and mechanical tests all showed better healing effect than other control groups.Conclusion:1.Li~+@MSNs/PEUU system has more sustained releasing effect than Li~+/PEUU system,and shows perfect mechanical properties and biocompatibility.The lithium salt released into the microenvironment has a good effect of promoting osteogenesis and inhibiting adipogenesis.2.Through the analysis of histology,biomechanics and micro-CT results,Li~+@MSNs/PEUU electrospinning mat can promote tendon-bone healing and inhibit fat infiltration of rotator cuff muscle at the same time.