Controlled Release Of GAG/MOF Core-shell Fiber Scaffold For Cartilage Regeneration

Osteoarthritis（OA）is a common chronic joint disease caused by trauma,congenital abnormalities,and overstrain,affecting the health and quality of life of more than 250 million people worldwide.Osteoarthritis mainly occurs in the joint area and surrounding tissues,and is characterized by degenerative cartilage damage and synovial inflammation.The key to its treatment includes regulating the cartilage microenvironment,suppressing the inflammatory response and promoting cartilage regeneration.However,since cartilage tissue has no blood vessels,nerves or lymphatic distribution,its repair and regeneration ability after injury is extremely poor,and there is no ideal treatment for cartilage degeneration injury caused by osteoarthritis.Tissue engineering technology based on biodegradable scaffolds may provide a feasible strategy to suppress joint inflammation and repair cartilage defects.Fibrous scaffolds prepared by electrospinning technology can highly mimic the microscopic morphology of natural extracellular matrix and have been one of the hot directions for tissue engineering scaffold preparation.In order to effectively promote cartilage regeneration,the core-shell fibrous scaffold was firstly prepared by coaxial solution electrospinning technique,in which synthetic poly（l-lactic acid）（PLLA）with good biocompatibility was used as the fibrous shell layer,and gelatin（Gel）with high hydrophilicity and cell binding sites was introduced into the shell layer,while glycosaminoglycan（GAG）,the main component of cartilage extracellular matrix,was introduced into the fibrous core layer,including hyaluronic acid（HA）and chondroitin sulfate（CS）.The effects of the content of each component on the physicochemical properties of the composite fibrous membrane and its regulation of chondrogenic differentiation of bone marrow mesenchymal stromal cells（BMSCs）were systematically characterized.The results showed that the prepared core-shell fibers had a controlled release effect on the loaded GAG components,and the hydrophilicity and cell affinity of the membranes increased with the increase of the gelatin percentage in the shell layer of the fibers,and the cell proliferation and live/dead staining characterized that all the membranes were free of significant cytotoxicity.We confirmed that the introduction of GAG into fibers could effectively promote the expression of chondrogenic differentiation markers in BMSCs cultured on membranes.Secondly,from the perspective of simulating the hypoxic state of natural cartilage and suppressing the local inflammatory,magnesium-gallate metal-organic framework nanoparticles（Mg-GA MOF）were synthesized in this study by hydrothermal method and introduced into the inside layer of core-shell fibers by coaxial electrospinning,aiming to stimulate the upregulation of hypoxia-inducible factor expression through the introduction of Mg²⁺retardation and alleviate inflammatory responses via the release of anti-inflammatory molecule gallic acid（GA）to reduce the adverse effects on cell/tissue biological behaviors.The results showed that MOF particles were successfully introduced into the interior of the aforementioned core-shell fibers and achieved the release of Mg²⁺and GA;the fibers were not significantly cytotoxic and supported the growth of BMSCs,macrophages（RAW 264.7）and chondrocytes obtained from the lesion sites of OA patients.Compared with the fibrous membrane without MOF,it was found that the fibrous membrane loaded with both GAG/MOF had stronger effects on promoting the differentiation of BMSCs toward cartilage and promoting the polarization of RAW 264.7 toward the anti-inflammatory M2 phenotype,with upregulated expression of hypoxia-inducible factors,while more significantly converting OA chondrocytes from abnormal to normal chondrocyte morphology.Finally,this study carried out in vivo evaluations by implanting composite fibrous membranes subcutaneously in the back of SD rats,with samples being collected at 1-7 days to assess inflammation modulation and at1-2 months to judge ectopic chondrogenic tendency.The outcomes confirmed that core-shell fibers loaded with both GAG/MOF had the most significant anti-inflammatory and chondrogenic effects with good biocompatibility by histological staining,immunofluorescence staining and immunohistochemical characterization.The results showed that the core-shell fibers loaded with GAG/MOF had the most significant anti-inflammatory and chondrogenic effects and were biocompatible.In conclusion,the simultaneous loading of bioactive components with chondrogenic and anti-inflammatory effects into fibrous scaffolds with biomimetic extracellular matrix morphology is expected to be used for the regeneration and repair of degenerated articular cartilage in the case of osteoarthritis through tissue engineering strategies.