Effects of mechanical vibrations on chondrocytes in monolayer culture for regenerative cartilage

Abstract

Cartilage regenerative medicine requires time and effort to regenerate thick hyaline cartilage. In this study, we investigated the effects of mechanical vibrations on chondrocyte proliferation and cartilage matrix production to simplify the regenerative medicine procedure. Chondrocytes were harvested from the metatarsophalangeal joints of pigs. Isolated chondrocytes were cultured in a monolayer without a scaffold for up to 26 days. Mechanical vibrations at 12.5, 25, and 50 Hz of 0.5 G were applied to a culture plate. Cell morphology, cell counting, tissue staining of proteoglycan and type II collagen, and real-time reverse transcription polymerase chain reaction were performed. The target genes were type II collagen, aggrecan, SOX9, type I collagen, and fibronectin. No significant difference in cell counts was observed at any of the measurement dates. Tissue staining showed that the cultured cartilage tissue contained hyaline cartilage matrices. The 25 Hz and 0.5 G mechanical vibration significantly increased the gene expression levels of type II collagen, aggrecan, fibronectin, and type I collagen by approximately 4.4, 3.4, 3.2, and 4.8 folds, respectively, compared to the static state. This suggests that the 25 Hz and 0.5 G mechanical vibration is beneficial for cultured cartilage transplantation in a simple procedure, providing the cultured cartilage with more hyaline cartilage characteristics, higher adhesion to cartilage defects, and greater strength than in the static state. Additionally, the gene expression levels of type I and II collagens at 25 Hz were significantly higher than those at 12.5 Hz and 50 Hz under the 0.5 G mechanical vibrations. This indicates that mechanical vibrations have a frequency-dependent effect on the gene expression of type I and II collagens.