Effect of Plasminogen Activator Inhibitor-1 on extracellular matrix homeostasis in scaffold-free spheroids from human chondrocytes

Introduction

New trends in osteoarthritis research focus on the use of biological therapy; in this context, the use of Plasminogen Activator Inhibitor-1 (PAI-1) is considered a potential therapeutic strategy to prevent extracellular matrix (ECM) degradation in osteoarthritis (OA) management. However, in vitro studies have not demonstrated its effect on the expression of ECM homeostasis-related genes.

Methods

Human OA cartilage-derived chondrocytes were used to generate scaffold-free spheroids under hypoxia conditions. The spheroids were exposed to PAI-1 for 24 h, and cell viability was measured. Then qRT-PCR was used to analyze the expression of ECM components and degradative enzymes, including COL2A1, SOX9, ACAN, COL1A1, MMP3, MMP9, MMP13, ADAMTS4, ADAMTS5, TIMP1, TIMP2, TIMP3, uPA and tPA.

Results

PAI-1 treatment consistently maintained cell viability and chondrocyte spheroid integrity. At the 50 ng/mL concentration, PAI-1 increased the gene expression of COL2A1 and reduced SOX9, ACAN, MMP3, MMP9, TIMP2, and tPA. Moreover, the functional COL2A1/COL1A1 ratio was significantly increased in PAI-1-treated spheroids.

Conclusion

Our results suggest that PAI-1 treatment exerts a complex and multifaceted influence on spheroids’ ECM. While it supports matrix integrity by reducing the gene expression of ECM remodeling enzymes, such as MMPs and ADAMTS5, it also induces unfavorable changes in chondrogenesis-related marker genes, such as SOX9 and ACAN. These findings indicate that the cellular response to PAI-1 is not unidirectional, warranting further investigation to understand its precise biological implications.