Using proteomics to analyse how ageing and senescence affect tissue mechanics and mechanotransduction

UoM administered thesis: Phd

  • Authors:
  • Venkatesh Mallikarjun

Abstract

The ageing process modifies the mechanical properties of tissues, making them more susceptible to damage and potentially affecting mechano-sensitive signalling pathways. Here, I have applied high-content imaging, transcriptomics and proteomics to interrogate the effects of in vivo ageing and in vitro senescence on matrix and mechanotransduction pathways. In vivo ageing was assessed in mouse skin – a tissue with an important mechanical role. In vivo skin ageing was associated with increased tissue stiffness and decreased elasticity, but these observations were not replicated in ovariectomized mice (a model of estrogen deprivation), despite broad correlation in protein changes assessed by label-free proteomics. This work suggested the importance of extracellular effects, such as matrix crosslinking, in determining the mechanical properties of aged tissue. In vitro senescence was assessed in primary human mesenchymal stem cells (MSCs) – a model system with well-characterised mechano-responses and potential applications in regenerative medicine. We developed a novel computational algorithm for systems biology analysis of the behavior of proliferative and senescent MSCs grown on synthetic substrates of different stiffnesses. Multi-omic characterization showed that senescent MSCs possessed a diminished response to changing substrate stiffness and their intracellular proteome reflected that of a stiff cell, regardless of actual substrate stiffness. Senescent MSCs grown on stiff substrates showed a specific decrease in type-I collagen (similar to aged mouse skin), as well as decreases in fibronectin, fibulins and tenascin, suggesting that substrate stiffness was still able to modulate progression of the senescence phenotype. Importantly, pharmacological release of cell contractility in proliferative MSCs was able to recapitulate senescence-associated changes in matrix proteins on stiff substrates. The study concluded that age-related perturbations in cytoskeletal mechanics inhibit proper mechano-signalling and therefore affect regulation of the extracellular matrix.

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Original languageEnglish
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Award date1 Aug 2019