TGF-β1-supplemented decellularized annulus fibrosus matrix hydrogels promote annulus fibrosus repair

Annulus fibrosus(AF)repair remains a challenge because of its limited self-healing ability.Endogenous repair strategies combining scaffolds and growth factors show great promise in AF repair.Although the unique and beneficial characteristics of decellularized extracellular matrix(ECM)in tissue repair have been demonstrated,the poor mechanical property of ECM hydrogels largely hinders their applications in tissue regeneration.In the present study,we combined polyethylene glycol diacrylate(PEGDA)and decellularized annulus fibrosus matrix(DAFM)to develop an injectable,photocurable hydrogel for AF repair.We found that the addition of PEGDA markedly improved the mechanical strength of DAFM hydrogels while maintaining their porous structure.Transforming growth factor-β1(TGF-β1)was further incorporated into PEGDA/DAFM hydrogels,and it could be continuously released from the hydrogel.The in vitro experiments showed that TGF-β1 facilitated the migration of AF cells.Furthermore,PEGDA/DAFM/TGF-β1 hydrogels supported the adhesion,proliferation,and increased ECM production of AF cells.In vivo repair performance of the hydrogels was assessed using a rat AF defect model.The results showed that the implantation of PEGDA/DAFM/TGF-β1 hydrogels effectively sealed the AF defect,prevented nucleus pulposus atrophy,retained disc height,and partially restored the biomechanical properties of disc.In addition,the implanted hydrogel was infiltrated by cells resembling AF cells and well integrated with adjacent AF tissue.In summary,findings from this study indicate that TGF-β1-supplemented DAFM hydrogels hold promise for AF repair.

Mechanically conditioned cell sheets cultured on thermo-responsive surfaces promote bone regeneration

Cell sheet-based scaffold-free technology holds promise for tissue engineering applications and has been extensively explored during the past decades.However,efficient harvest and handling of cell sheets remain challenging,including insufficient extracellular matrix content and poor mechanical strength.Mechanical loading has been widely used to enhance extracellular matrix production in a variety of cell types.However,currently,there are no effective ways to apply mechanical loading to cell sheets.In this study,we prepared thermo-responsive elastomer substrates by grafting poly(N-isopropyl acrylamide)(PNIPAAm)to poly(dimethylsiloxane)(PDMS)surfaces.The effect of PNIPAAm grafting yields on cell behaviours was investigated to optimize surfaces suitable for cell sheet culturing and harvesting.Subsequently,MC3T3-E1 cells were cultured on the PDMS-g-PNIPAAm substrates under mechanical stimulation by cyclically stretching the substrates.Upon maturation,the cell sheets were harvested by lowering the temperature.We found that the extracellular matrix content and thickness of cell sheet were markedly elevated upon appropriate mechanical conditioning.Reverse transcription quantitative polymerase chain reaction and Western blot analyses further confirmed that the expression of osteogenic-specific genes and major matrix components were up-regulated.After implantation into the critical-sized calvarial defects of mice,the mechanically conditioned cell sheets significantly promoted new bone formation.Findings from this study reveal that thermo-responsive elastomer,together with mechanical conditioning,can potentially be applied to prepare high-quality cell sheets for bone tissue engineering.