The Stiffness-sensitive Transcriptome of Human Tendon Stromal Cells.

Extracellular matrix stiffness is a major regulator of cellular states in health and disease. Stiffness-sensing investigations are typically performed using cells that have acquired "mechanical memory" through prolonged conditioning in rigid mechanical environments, e.g. tissue culture plastic (TCP). This potentially masks the full extent of the matrix stiffness-driven mechanosensing programs. Here, a biomaterial system composed of two-dimensional mechano-variant silicone substrates with simplified and scalable surface biofunctionalization chemistry is developed to facilitate large-scale cell culture expansion processes. Using RNA sequencing, stiffness-mediated mechano-responses of human tendon-derived stromal cells are broadly mapped. Matrix rigidities approximating tendon microscale stiffness range (E. ∼35 kPa) distinctly favor transcriptional programs related to chromatin remodeling and Hippo signaling; whereas more compliant stiffnesses (E. ∼2 kPa) are enriched in responses related to cell stemness, synapse assembly and angiogenesis. While tendon stromal cells undergo dramatic phenotypic drift on conventional TCP, mechano-variant substrates abrogate this activation with tenogenic stiffnesses inducing a transcriptional program that strongly correlates with established tendon tissue-specific expression signature. Computational inference predicted that AKT1 and ERK1/2 are major signaling hubs mediating stiffness-sensing in tendon cells. Together, these findings highlight how extracellular matrix biophysical cues may dictate the transcriptional identity of tendon resident cells, and how matrix mechano-reciprocity regulates diverse sets of previously underappreciated mechanosensitive processes in tendon fibroblasts. This article is protected by copyright. All rights reserved.