Objective: The genomic effects of biomechanical loading on human growth plate cartilage are unknown so far. To address this, we used rare human growth plate biopsies obtained from children undergoing epiphysiodesis and exposed them to precisely controlled mechanical loading using a microloading device. The biopsies were cultured 24 hours after mechanical loading, followed by RNA-sequencing analyses to decipher the genomic regulation.
Design: We conducted RNA-seq analysis of human growth plate cartilage obtained from three patients cultured ex vivo and subjected to cyclical mechanical loading with peak 0.4 N with frequency 0.77 Hz during a 30-second duration, using a specialized microloading device.
Results: Gene ontology analysis revealed novel data showing three significantly upregulated signaling pathways, including notch, oxytocin, and tight junction, and three significantly downregulated signaling pathways, including lysosome, sphingolipid metabolism, and peroxisome proliferator-activated receptor (PPAR) in human growth plate cartilage. Moreover, we found 15 significantly regulated genes within these signaling pathways from all three patients. These genes included PSEN2, HEY1, and NCOR2 from the notch signaling; CACNB1 and PPP3R2 from the oxytocin signaling; ACTR3C, WHAMM, and ARHGEF18 from the tight junction signaling; ARSA, SMPD1, and CD68 from the lysosome signaling; ARSA and SMPD1 from the sphingolipid metabolism signaling; and SLC27A4 and AQP7 from the PPAR signaling pathway. In addition, 20 significantly upregulated genes and six significantly downregulated genes shared between two patient samples were identified.
Conclusion: Our study provides the first-ever transcriptomic data of mechanical loading of human growth plate cartilage. These findings can potentially provide genetic targets for future investigations in physiological and pathological bone growth conditions.
Keywords: RNA-seq; biomechanical loading; chondrocytes; genomic; human growth plate.