Double-layer Composite Scaffold For Repairing Osteochondral Injury

Osteochondral injury is a common orthopedic disease that usually causes arthritic manifestations.Since cartilage itself is difficult to achieve self-repair,osteochondral repair has always been a considerable challenge.With the continuous development of tissue engineering technology,new ideas have emerged in the repair of osteochondral.Scaffolds,seed cells and growth factors are the three elements of tissue engineering to repair osteochondral injury.Seed cells can proliferate and differentiate into target cells to repair tissue damage.Scaffolds provide seed cells with a proliferative and differentiated environment,and growth factors can promote the repair process.In the past few decades,a large number of ideas about osteochondral repair have been proposed,and some have been promoted and applied clinically as products.However,it is difficult to satisfy the repairing needs of two different tissues of cartilage and bone at the same time.Therefore,we propose to use double-layer scaffold material to realize the integrated repair of osteochondral.To this end,a bionic bilayer scaffold consisting of methoxy poly(ethylene glycol)-block-poly(L-valine)(mPEG-b-PLV)thermogel and porous poly(lactide-co-glycolide)/hydroxyapatite(PLGA/HA)scaffold was prepared(Fig.1).For better therapeutic effect in cartilage defect,kartogenin(KGN)and mesenchymal stem cells(MSCs)were introduced into mPEG-b-PLV thermogel.KGN is a small molecule cartilage-inducing factor that can promote differentiation of MSCs into chondrocyte and also shows cartilage protective effects.Moreover,PLGA/HA was immobilized with bone morphogenetic protein 2(BMP-2)by polydopamine to facilitate the repair of subchondral bone.BMP-2 is the first commercially available growth factor for bone regeneration with strong osteoinduction effect.polydopamine modification improves the hydrophilicity of PLGA/HA,which facilitates cell adhesion and also assists in immobilizing BMP-2 to PLGA/HA.This bionic bilayer scaffold achieved sustained release of KGN and BMP-2,and provided specialized microenvironment for the reconstruction of cartilage and subchondral bone.In summary,the biomimetic bilayer scaffold provides a promising prospect for the integrated reconstruction of cartilage and subchondral bone,which is worthy of further preclinical evaluation.