Application Of An All-silk-derived Composited Biphasic Hydrogel Scaffold In Osteochondral Tissue Engineering

BackgroundOsteochondral injury is the earliest manifestation of osteoarthritis.As an avascular tissue,articular cartilage lacks the capability to self-heal after damaged.Osteochondral injury often progresses to the destruction of the entire joint,causing health problems in nearly one fifth of elderly population worldwide.At present,there is still a lack of effective treatment strategy to repair it and reverse the progression of osteoarthritis.However,with the development of tissue engineering,osteochondral regeneration scaffolds show great potential in defect repair.The key to develop a practicable osteochondral regeneration scaffold is the masterly combination of scaffold materials,cells and signaling factors.Here we try to give a solution to this problem.ObjectiveSilk fibroin(SF)with good biocompatibility,high mechanical strength and editable structure was used as the main component of the scaffold.Platelet-rich plasma(PRP)and berberine(BBR),which have been widely test in clinical practice,were used to recruit tissue repairing cells and promote the regeneration of subchondral bone layer.Kartogenin(KGN)was introduced to promote the regeneration of cartilage layer.By combining above four components,an all-silkderived composited biphasic hydrogel was fabricated to repair osteochondral defects.Method1.Prepare SF solution and synthesize Methacrylated silk fibroin(SilMA),which is photocurable.The physical property of them were evaluated.2.Fabricate SF nano-and microspheres,and drug-loading SF microspheres with BBR(SF-BBR microspheres)and KGN(SF-KGN microspheres).The property of them were evaluated.3.Fabricate and activate PRP.By combining SilMA,PRP,SF-BBR microspheres and SF-KGN microspheres,an all-silk-derived composited biphasic hydrogel was fabricated.The physical property and osteochondral tissue repair capacity in vitro and in vivo of the as-prepared hydrogel were evaluated.Result1.The scaffold formed by 30%SilMA hydrogel showed good pore structure and pore connectivity,good swelling capacity,strong mechanical property and slow in vitro degradation rate.2.Nano-and microspheres with different diameter can be fabricated by adjusting SF concentration.BBR and KGN were successfully encapsulated into 10%SF microspheres,and the drug loading rates were 4.31%and 3.16%,respectively.3.PRP was successfully fabricated.30%SilMA hydrogel combining PRP,SFBBR microspheres and SF-KGN microspheres,the composited biphasic hydrogel also showed good pore structure and pore connectivity,good swelling capacity,strong mechanical property,slow in vitro degradation rate and good biocompatibility.4.BBR and KGN can be sustainably released in vitro for up to 90 days from SFBBR microspheres and SF-KGN microspheres,respectively.5.PRP can significantly promote the migration of bone marrow mesenchymal stem cells(BMSCs)within six hours at low concentrations.10μM BBR and KGN can significantly promote BMSCs osteogenic and chondrogenic differentiation,respectively.Results mentioned above can be repeated when SilMA hydrogels combining with PRP,SF-BBR microspheres and SF-KGN microspheres were test.6.Under inflammatory condition,the as-prepared composited hydrogels can promote BMSCs osteogenic and chondrogenic differentiation as well.To some extent PRP have a synergistic effect on inducing BMSCs osteogenic and chondrogenic differentiation by BBR and KGN.7.After eight weeks of implantation,the all-silk-derived composited biphasic hydrogel showed satisfactory bone and cartilage regeneration capacity.ConclusionThe in vitro and in vivo studies indicated that the all-silk-derived composited biphasic hydrogel had satisfactory bone and cartilage biphasic tissue regeneration capacity.Most of its components,including SF,PRP and BBR,have been certified in clinical practice.This study provides a new idea for the development of an osteochondral engineering scaffold with clinical potential.