Abstract
Autologous chondrocyte implantation (ACI) has long been regarded as the gold-standard chondrocyte-based therapy for articular cartilage repair. The main challenge in ACI is that chondrocytes lose their chondrogenic phenotype after monolayer expansion in vitro. The monolayer-expanded chondrocytes show dedifferentiation and senescence, hindering their ability to synthesize hyaline cartilage. Currently, there is no effective method to alleviate dedifferentiation and senescence in these monolayer-expanded chondrocytes. Adipose-derived stem cells (ADSCs) have been increasingly explored as a viable alternative cell source to chondrocytes for articular cartilage tissue engineering. Besides inducing chondrogenesis of ADSCs into chondrocyte, recent research emphasizes the positive impact of ADSC-secreted extracellular vesicles (ADSC-EVs). We demonstrate that ADSC-EVs alleviate dedifferentiation and senescence in monolayer-expanded chondrocytes, enhancing their capacity to produce hyaline cartilage. The ADSC-EVs treatment redifferentiated the monolayer-expanded chondrocytes by upregulating collagen type II (Col-II), sulfated glycosaminoglycan (sGAG), and SOX-9 expression and decreasing collagen type I (Col-I) levels. The redifferentiated chondrocytes also showed enhanced cell proliferation and reduced levels of P16 and senescence-associated β-galactosidase (SA-β-gal). Moreover, ADSC-EV treatment increased the ability of monolayer-expanded chondrocytes to synthesize hyaline cartilaginous matrices in 3D pellet culture. This effect is achieved through the suppression of interleukin-1β-induced mitogen-activated protein kinase (MAPK) signaling. Through next-generation sequencing and bioinformatic analyses, the miRNAs contained in ADSC-EVs were revealed as key candidates involved in mitigating dedifferentiation and senescence. Our findings propose a novel approach employing ADSC-EVs to restore the chondrogenic phenotype of monolayer-expanded chondrocytes, offering an alternative strategy for more effective ACI.