Mitochondria-engine with self-regulation to restore degenerated intervertebral disc cells via bioenergetic robust hydrogel design

Previous studies have confirmed that intervertebral disc degeneration(IDD)is closely associated with inflammation-induced reactive oxygen species(ROS)and resultant cell mitochondrial membrane potential(MMP)decline.Clearance of ROS in an inflammatory environment is essential for breaking the vicious cycle of MMP decline.Additionally,re-energizing the mitochondria damaged in the inflammatory milieu to restore their function,is equally important.Herein,we proposed an interesting concept of mitochondrion-engine equipped with coolant,which enables first to“cool-down”the inflammatory environment,next to restore the MMP,finally to allow cells to regain normal energy metabolism through materials design.As such,we developed a multifunctional composite composed of a reactive oxygen species(ROS)-responsive sodium alginate/gelatin hydrogel infused into a rigid 3D-printed thermoplastic polyurethane(TPU)scaffold.The TPU scaffold was coated with conductive polypyrrole(PPy)to electrophoretically deposit L-arginine,which could upregulate the Mammalian target of rapamycin(mTOR)pathway,thus increasing MMP and energy metabolism to stimulate extracellular matrix synthesis for IVD repair.While the ROS-responsive hydrogel acting as the“mito-engine coolant”could scavenge the excessive ROS to create a favorable environment for IVD cells recovery.Demonstrated by in vitro and in vivo evaluations,the mito-engine system markedly promoted the proliferation and collagen synthesis of nucleus pulposus cells while enhancing the mitochondrial respiration and MMP under oxidative stress.Radiological and histological assessments in vivo revealed the efficacy of this system in IVD repair.This unique bioinspired design integrated biomaterial science with mitochondrial biology,presents a promising paradigm for IDD treatment.

Corrigendum to“Mitochondria-engine with self-regulation to restore degenerated intervertebral disc cells via bioenergetic robust hydrogel design”[Bioact.Mater.40C(2024)1–18]

The authors regret that in Fig.2Aa of the article,the images for TPUPPy and TPU-aa in the first column were mistakenly duplicated due to a formatting error.The correct version of Fig.2 is provided below,along with the original data for reference.The authors confirm that the rest of the article remains unaffected.

3D-printed auxetic-structured intervertebral disc implant for potential treatment of lumbar herniated disc

In this study,a novel artificial intervertebral disc implant with modified“Bucklicrystal”structure was designed and 3D printed using thermoplastic polyurethane.The new implant has a unique auxetic structure with building blocks joined“face-to-face”.The accompanied negative Poisson’s ratio enables its excellent energy absorption and stability under compression.The deformation and load distribution behavior of the implant under various loading conditions(bending,torsion,extension and flexion)has been thoroughly evaluated through finite element method.Results show that,compared to natural intervertebral disc and conventional 3D implant,our new implant exhibits more effective stress transfer and attenuation under practical loading conditions.The implant’s ability to contract laterally under compression can be potentially used to alleviate the symptoms of lumbar disc herniation.Finally,the biocompatibility of the implant was assessed in vitro and its ability to restore the physiological function of the disc segment was validated in vivo using an animal model.