A Tranilast And BMP-2 Based Functional Membrane Is Effective For The Prevention Of Epidural Fibrosis During Spinal Lamina Reconstruction

Objective:With the extensive development of lumbar surgery,the incidence of failed back surgery syndrome has increased significantly,which seriously affects the quality of life of patients.FBSS is a common complication of lumbar surgery.Epidural fibrosis is one of the major cause of FBSS,with no effective therapeutic treatment for it.In this study,a CS/PLGA-MBG bilayer membrane loaded with tranilast（TNL）and BMP-2 was used to reconstruct the vertebral plate and the level of epidural fibrosis was assessed in the rabbit laminectomy model.We hope that the membrane can prevent the FBSS.Methods:1.CS/PLGA-MBG bilayer membranes was prepared by supercritical carbon dioxide（sc-CO₂）foaming and freeze-drying method.TNL was loaded on CS layer and BMP-2 was loaded on PLGA-MBG layer.2.To detect the structure of CS/PLGA-MBG membranes and the drug release speed after loading.3.Rabbit models of laminectomy were prepared.The membranes were placed in the site of laminectomy and fed for 4 weeks and 12 weeks.After sacrificing,micro-CT was used to detect the formation of bone in the surgical area.Sections were stained with Masson Trichrome,Safranine O-Fast Green and Hematoxylin&Eosin to observe the bone formation and fibrosis at the site of laminectomy.4.CCK8 and Western Blot methods were used to observe the regulation of tranilast on the proliferation and fibrosis of mouse fibroblasts（L929）in vitro.ALP staining and osteogenesis-related gene expression detection were used to observe the regulation of tranilast on the osteogenic differentiation of mouse mesenchymal stem cells（mMSC）.Results:1.The prepared CS/PLGA-MBG membranes have pore structure,and the pore structure of the two layers is different.2.CS/PLGA-MBG membranes can be loaded with tranilast and BMP-2 respectively,and can be released for a long time in vitro.3.Results revealed that whilst laminectomy site in control group was filled with disordered fibrous tissue that had invaded the dura mater,no fibrous tissue formation nor invasioin was observed in TNL/BMP2 treated group.Furthermore,new bone formations at the laminectomy site was also observed in experimental group loaded with TNL/BMP-2.4.In vitro cellular and molecular studies found that TNL reduced osteogenic differentiation of murine MSC cells and fibrosis formation by downregulating p65phosphorylation and nuclear translocation thereby inhibiting NF-κB signaling.Conclusions:The CS/PLGA-MBG bilayer membrane combines the anti-fibrotic effect of CS and osteoinductive effects of PLGA-MBG for effective bone healing and regeneration,and prevents epidural fibrosis formation.Additionally,incorporation of anti-fibrotic agent TNL and osteogenic factor BMP-2 onto CS and PLGA-MBG respectively,further enhances the anti-fibrosis and osteogenic potential of the bilayer membrane.