Transcriptome profiling of tendon fibroblasts at the onset of embryonic muscle contraction reveals novel force-responsive genes

Abstract

AbstractAll cells are exposed to mechanical forces and must adapt to their physical environments but the underlying adaptive mechanisms remain unclear. To address this in developing tendons exposed to the extreme forces of muscle contraction, we have performed transcriptomics with tendon fibroblasts (tenocytes) isolated from zebrafish embryos before and after they start to swim. We find upregulation of known tenocyte markers as well as dramatic changes in expression of many novel tendon-associated genes. By paralyzing and restoring muscle contractions in embryos in vivo, we show that three of these novel genes, ECM proteins Matrix Remodeling Associated 5b (mxra5b) and Matrilin 1 (matn1), as well as the transcription factor Kruppel-like factor 2a (klf2a), are force-responsive. In situ hybridization validates tendon-specific expression of all three genes. Quantitation using in situ hybridization chain reaction reveals that their transcript levels change specifically in subsets of tenocytes in response to force. These findings provide insights into force-dependent feedback mechanisms in tendons, which have important implications for improved treatments for tendon disease, injury and atrophy.