Bidirectional and Mutually Beneficial Interactions Between Human Mesenchymal Stem Cells and Osteoarthritic Chondrocytes in Micromass Co-Cultures

Abstract

Mesenchymal stem cell (MSC)-based therapy presents a promising approach for treating osteoarthritis (OA). However, the molecular interactions between MSCs and OA chondrocytes (OACs) are not known. This study aims to investigate the bidirectional interactions between human MSCs (hMSCs) and human OACs (hOACs) in a 3D co-culture system. hMSC-collagen microspheres were cultured in hOAC-conditioned medium or co-cultured with hOAC-collagen microspheres. Growth characteristics, glycosaminoglycan (GAG) production, gene expression of major OA-associated chondrogenic markers, including SOX9, COL2A1, ACAN and MMP13, were investigated in both cell types. Both the conditioned medium and the co-culture induced MSC chondrogenesis with enhanced GAG production, SOX9 gene and protein expression, and gene expression of ACAN and COL2A1. Meanwhile, the co-culture also induced hOACs to partially resume the lost chondrogenic phenotype as shown by reduced proliferation, enhanced GAG production when hMSCs were chondrogenically predifferentiated, and reduced MMP13 gene expression. This work suggests that 3D co-culture of hMSCs and hOACs is mutually beneficial to each other, suggesting the potential therapeutic effect of delivering hMSC in scaffolds directly to OA defects.