| Intervertebral disc degeneration(IVDD)increases the risk of low back pain and causes a severe economic and health burden in society.IVDD is observed by the age of 10 with a decrease in the number of chondrocyte-like cells,leading to the degradation of the extracellular matrix.IVDD has many causes,among which inflammation plays an important role.The phytochemicals extracted from medicinal plants abundant in flavonoids and polyphenols are well known for their anti-inflammatory,anti-oxidative and anti-tumorigenic properties.Wogonin,a naturally existing monoflavonoid,has been proven to be an effective anti-inflammatory agent in a variety of diseases.Hence,we hypothesized that wogonin might reduce inflammation in nucleus pulposus cells(NPCs)during intervertebral disc degeneration.We first eatablished In vitro inflammatory model by stimulating NPCs with IL-1?.Then we detected the anti-inflammatory effect of wogonin in rat NPCs.This study also investigates the underlying mechanisms of wogonin and its potential use in preventing disc degeneration in a rat caudal vertebrae needle-stab model.In vitro we have performed molecular techniques such as western blot,PCR,immunofluorescence and found that wogonin could effectively inhibit the IL-1?-induced upregulation of inflammatory mediators and matrix degradation related enzymes such as MMPs and AD AMTS.Besides,down-regulation of extracellular matrix such as collage II in rat nucleus pulposus cells was also reversed by wogonin.Furthermore,we found that wogonin mainly exerts anti-inflammatory effects through Nrf2/ARE signal axis and MAPK pathway.In vivo we found wogonin could inhibit the progress of disc degeneration in rat caudal vertebrae needle-stab model by histological and imaging techniques.Due to the lack of vascularity in intervertebral disc,we usually adopt local region injection aiming to achieve high concentration of therapeutic agents in the vicinity of nucleus pulposus cells.However,the short half-lives,poor solubility and poor retention of these agents in the injection area will lead to increase of administration frequency,dose and toxicity,which may dramatically hinder their therapeutic applications.And repeated injection in the intervertebral disc will also cause injuries.Besides,the dense extracellular matrix can also prevent the penetration of the agents.Thus,it is urgent to devise a drug delivery system that can overcome these weaknessesHence,we modified wogonin to obtain better properties.We reported the fabrication of CAP peptide functionalized PEG-b-PCL micelle as a novel nano drug delivery system The sequence of the peptide is DWRVIIPPRPSA.Co-solvent evaporation method was utilized to prepare this drug-carrying nano complex and some material characterization tests were performed to evaluate this complex.Wogonin was loaded inside the nanocarrier to assess its effect in ameliorating the intervertebral disc degeneration compared with the wogonin monomer.Coumarin 6 was encapsulated inside the nanocarrier as a fluorescent probe to explore the drug-releasing ablity,the nucleus pulposus uptake efficiency and the endocytosis pathway involved in this process.In the meanwhile,we encapsulated the fluorescent dye Cy7 into the nanocarrier to simulate the retention of wogonin-loaded micelles in vivo.The results indicate that the drug delivery systems we have devised possess great agent-releasing capacity,and the CAP peptide modified drug-loading micelles can target nucleus pulposus effectively,sustain longer and perform better compared with wogonin monomerAll taken together,our research demonstrates wogonin can mitigate intervertebral disc degeneration by inhibiting the inflammation effects.Nrf2 will be a promising target spot in disc degeneration therapy.The combination of novel nano drug delivery system and tranditional agent will also provide a new insight for us. |
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