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This study designed a novel porous PDLLA microspheres/collagen gel composite combined with fibroblasts as the injectable dermal filler for soft-tissue augmentation.The low degradation rate of porous PDLLA microspheres and seed cells were introduced in the system to achieve the filling volume stability and stronger regeneration activity.Biodegradable PDLLA porous microspheres were prepared by an improved water-in-oil-in-water double emulsion solvent evaporation method.The combine of fibroblasts with porous microspheres was observed through co-culture of cells with microspheres,SEM (scanning electron microscope) and fluorescent staining technology.The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay,the hemolysis test and histocompatibility experiment indicated that the composite had satisfactory biocompatibility in vitro and in vivo.In the animal studies,the composite was implanted into the subcutaneous part of the rats' back through sterile needles.The collagen was metabolized within 30 days,meanwhile,fibroblasts-porous PDLLA micro-spheres served as scaffold structure and seed cells which promote new connective tissue formation.The histo-pathological studies demonstrate that the fibroblasts-porous PDLLA microspheres/collagen gel composite group could create larger amount of supportive structure than PDLLA porous microspheres/collagen gel composite group.All the results indicate that fibroblasts-porous PDLLA microspheres/collagen gel composite may have great clinical application in soft-tissue augmentation with its excellent biocompatibility,regeneration activity and stable long-term filling ability.