A cell-free therapy for articular cartilage repair based on synergistic delivery of SDF-1 & KGN with HA injectable scaffold

This study was to co-encapsulate a chemokine (stromal cell-derived factor-1, SDF-1) and a chondroinductive molecule (kartogenin, KGN) within microspheres via microfluidics, and to incorporate them into a hyaluronic acid (HA) injectable scaffold for articular cartilage defect repair. HA injectable scaffold, as a cartilage-friendly microenvironment, was prepared by crosslinking HA with 1,4-butanediol diglycidyl ether. A microfluidic device was set up to prepare monodisperse PLGA microspheres (49 μm) to load SDF-1 and KGN. An in vivo model of full-thickness articular cartilage defects in rabbits was applied to evaluate the reparative capacity of the current package. The SDF-1 and KGN were co-encapsulated simultaneously within the core and shell area of the microsphere with high loading efficiency and sustained release profiles of more than 2 months. The release profiles of them were highly matched and well fitted to a first-order mathematical model. These microspheres when incorporated into HA injectable scaffold were demonstrated to heal the full-thickness articular cartilage defects in rabbits. The regenerated tissue had the typical cartilage histological characters and integrated well with the surrounding tissue at 12w. This developed cell-free system could serve as an efficient therapy for articular cartilage defects treatment, serving as a supplementary way to cell based therapies.