The Role Of Anti-inflammatory Effect Of Hyaluronic Acid Gel In Modifying Polymer Scaffold And In Suppressing Keloid Cell Pathological Phenotype

OBJECTIVE: Hyaluronic acid(HA)is a hydrophilic polymer and can serve as a medium buffer to reduce the host inflammatory response in vivo.Polyglycolic acid(PGA)is also a commonly used tissue engineering polymer scaffold.PGA can be hydrolysised which results in releasing acidic degradation products,giving rise to severe host inflammatory response and impair the quality of engineered tissues.In this study,modification of PGA non-woven fibers with HA coating was performed in order to to improve the biocompatibility and investigate its role in regulating inflammatory reaction both in vitro and in vivo,as well as to explore the inhibitory effect of hyaluronic acid on the pathological phenotype of in vitro cultured keloid fibroblast(KFs).METHODS: PGA scaffolds coated with 0.25%,0.5%,1% HA solution were served as the experimental groups and non modified ones were served as control.4 weeks of in vitro hydrolysis experiments were carried out on different groups of materials and the changing of p H and weight were measured.The above mentiond materials were implanted into the subcutaneous tissus of rabbits for 2 weeks and 4 weeks,then harvested for histological examination.Human dermal fibroblasts were seeded into uncoated and 1%HA coated PGA scaffolds.After 7 days of in vitro culture,q PCR was used to detect the gene expression of inflammation-related factors.The above mentioned materials were also applied for cartilage engineering both in vitro(4 weeks and 8 weeks)and in vivo(8weeks)and were valued by histochemical staining,total collagen content and GAGs content quantification as well as q PCR test on the cartilage-related gene expression.Human KFs were incubated with different concentrations of HA in vitro,and then the CCK-8 assay and q PCR test was applied to the cultured cells.Also,the cell migration out of the explant was investigated and compared with the control groupRESULTS: Scanning electron microscopy showed that the higher concentration of HA was more effective in coating PGA scaffolds than low concentration HAs.It could also alleviate the acidity of PGA fiber degradative product,but had no obvious effect on PGA degrading rate.High concentration of HA coating was able to effectively reduce the tissue inflammatory response of implanted PGA scaffold,reduce tissue vascularization and cell death and promote cell infiltration;in vitro experiments demonstrated that 1%HA coating could improve cell adhesion to PGA scaffolds and reduce the gene expression of IL-1,IL-6,IL-8 and α-SMA.The 1% HA coated PGA scaffold could engineer better quality cartilage tissue with more total collagens,GAGs and higher gene expression levels of collagen II,aggrecan and Sox 9(at 4 weeks and 8 weeks)and collagen X(only 8 weeks).There were no significant differences in gross and histological examination between the two groups for in vivo engineered cartilage,but the modified group produced higher level of GAGs.Adding different concentrations HA into cultured KFs could inhibit KFs pathological phenotype,including the reduction of cell proliferation and migration,as well as the gene expression of inflammatory cytokines.CONCLUSION: HA coating modification can improve the biocompatibility of PGA scaffold,including the reduction of the acidity of degradation products,reduced inflammatory response after implantation and improved quality of engineered tissue.At the same time,HA treatment can help to inhibit the pathological phenotype of cultured KFs.