Immunomodulatory exosomes loaded chitosan methacryloyl hydrogel combined with pro-chondrogenic microspheres for promoting articular cartilage regeneration

• The exosomes reduce inflammatory microenvironment and MMP13, creating a favorable environment for subsequent regeneration stages. • A sequential release CSMA-EGCG-exо@ KGN yS microsphere-gel system can promote the secretion of cartilage specific extracellular matrix. • This study explores macrophage-involvement mechanisms in substance-mediated cartilage formation and factors affecting immune response. A diverse range of biological materials has been widely used for the management of injuries to joint cartilage. However, suboptimal outcomes in cartilage repair are often due to inappropriate host immune responses and inadequate microenvironments for chondrogenesis. Therefore, there is a need to develop innovative hydrogel systems with immunomodulatory capabilities that promote a favorable environment for cartilage regeneration. In this study, we fabricated a Chitosan Methacryloyl (CSMA) hydrogel and incorporated exosomes derived from lipopolysaccharide (LPS)-activated NR8383 macrophages stimulated with Epigallocatechin gallate (EGCG) (EGCG-exo). Additionally, Kartogenin (KGN)-incorporated poly (lactic-co-glycolic acid) (PLGA) microspheres (KGN μS) were added to the hydrogel to stimulate chondrogenic differentiation of recruited BMSCs upon KGN release. The immunomodulatory and pro-chondrogenic properties of the CSMA-EGCG-exo@KGN μS microsphere-gel system were evaluated both in vitro and in vivo. The CSMA-EGCG-exo@KGN μS system not only demonstrated macrophage reprogramming properties but also enhanced BMSC recruitment and promoted chondrogenesis, leading to improved cartilage regeneration in a rabbit model of cartilage lesions. Looking forward, the CSMA-EGCG-exo@KGN μS microsphere-gel system holds significant potential for clinical translation as a pro-regenerative implant material for the treatment of cartilage injuries.