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Snedeker, J. G.

Publications and source records attributed to Snedeker, J. G..

2 recordsLinked to original sources

The Protein Mat(ters) - Revealing Biologically Relevant Mechanical Contribution of Collagen and Fibronectin Coated Micropatterns

Understanding cell-material interactions requires accurate characterization of substrate mechanics, which are generally measured by indentation-type atomic force microscopy. Although model extracellular matrix coatings are used to facilitate cell-substrate adhesion, their tensile mechanical properties are generally unknown. In this study a novel tensile mechanical characterization of collagen and fibronectin micropatterned polyacrylamide hydrogels is performed. Our findings reveal that the protein coating itself has measurable and biologically relevant consequences, with ligand-specific tensile resistance of the patterned regions relative to the non-patterned surfaces. To our knowledge our study is the first to uncover a direction-dependent mechanical behavior of the protein coatings and to demonstrate that it affects cellular response relative to substrate mechanics.

cell biology

Tendon response to matrix unloading is determined by the patho-physiological niche

Aberrant matrix turnover with elevated matrix proteolysis is a hallmark of tendon pathology. While tendon disease mechanisms remain obscure, mechanical cues are central regulators. Unloading of tendon explants in standard culture conditions provokes rapid cell-mediated tissue breakdown. Here we show that biological response to tissue unloading depends on the mimicked physiological context. Our experiments reveal that explanted tendon tissues remain functionally stable in a simulated avascular niche of low temperature and oxygen, regardless of the presence of serum. This hyperthermic and hyperoxic niche-dependent catabolic switch was shown by whole transcriptome analysis (RNA-seq) to be a strong pathological driver of an immune-modulatory phenotype, with a stress response to reactive oxygen species (ROS) and associated activation of catabolic extracellular matrix proteolysis that involved lysosomal activation and transcription of a range of proteolytic enzymes. Secretomic and degradomic analysis through terminal amine isotopic labeling of substrates (TAILS) confirmed that proteolytic activity in unloaded tissues was strongly niche dependent. Through targeted pharmacological inhibition we isolated ROS mediated oxidative stress as a major checkpoint for matrix proteolysis. We conclude from these data that the tendon stromal compartment responds to traumatic mechanical unloading in a manner that is highly dependent on the extrinsic niche, with oxidative stress response gating the proteolytic breakdown of the functional collagen backbone.

molecular biology