From extracellular matrix rigidity to vascular ageing – RiVAge

We designed a multidisciplinary experimental plan using biochemical, biophysical and in vivo analyses with the following specific aims:
-Evaluate the contribution of Ras and its specific activators, RasGRF2 to the vascular alterations
observed in response to ageing-induced ECM stiffening.
-Evaluate the role of nuclear mechanotransduction pathways during vascular ageing.

Our preliminary results indicate that RasGRF2 activity is regulated by matrix rigidity

This proposal may allow identification of new pharmacological targets for age-associated cardiovascular diseases, which constitutes a major health problem. Indeed cardiovascular pathologies are the leading cause of death in both the developing and industrialized world and are projected to remain so in the future, as population aged 65 or over is increasing.

Our preliminary results were presented during a European cardiovascular research conference.

Ageing is a major risk factor for cardiovascular diseases, as over 80% of all cardiovascular deaths occurs in population aged 65 or over in developed countries. Thus, many efforts have been directed recently to understand how ageing induces morphological and functional changes in the vasculature. Within the arterial system, the extracellular matrix (ECM) becomes more rigid with age, as a result of extensive modifications, including elastin depletion and calcification. This excessive ECM rigidity affects arterial wall cell phenotype and growth, leading to inflammation and vascular remodeling, which exacerbate arterial stiffening and favor cardiovascular diseases, such as hypertension and atherosclerosis. Whereas the response of vascular cells to ECM stiffening seems to play a key role during vascular ageing, how do cells respond to ECM rigidity remains, so far, an open question.
Recent works have provided evidence for a critical role of actomyosin contractility in ECM rigidity sensing, demonstrating that cells continuously adjust to the stiffness of their physical environment by generating tension, which in turn activates signaling pathways and triggers the cellular adaptation to ECM rigidity. This indicates that the molecular mechanisms that "sense" and transduce mechanical tension into signaling pathways, i.e. mechanotransduction mechanisms, are central to the cellular response to ECM rigidity.
By combining biochemical and biophysical approaches, we recently found that mechanical tension on adhesions activates two mechanotransduction pathways which drive the cellular adaptation to tension: 1) a K-Ras-dependent cytosolic pathway that controls adhesion and cytoskeletal rearrangement (Guilluy et al., Nature Cell Biol., 2011) and 2) a Src-dependent nuclear mechanotransduction pathway which is activated after force transmission to the nucleus through the cytoskeleton.
Interestingly, we observed that K-Ras and its specific activator, RasGRF2, are activated in the cytosol when cells are grown on rigid substrates, while in the nucleus Src-mediated mechanotransduction pathway induces phosphorylation of nuclear protein, including potential transcription regulators. These preliminary results indicate that ECM rigidity activates both cytosolic and nuclear mechanotransduction pathways.
Our hypothesis is that these mechanotransduction pathways regulate the response of vascular cells to ECM stiffening and inhibition of these pathways may have protective effect against deleterious actions of vascular ageing. This project aims to identify the molecular actors of these cytosolic and nuclear mechanotransduction pathways and test their relevance as therapeutic targets to limit ageing-associated cardiovascular diseases development. To do so, we designed a multidisciplinary experimental plan using biochemical, molecular and in vivo analyses with the following specific aims:
-Evaluate the contribution of Ras and its specific activators, RasGRF2 to the vascular alterations observed in response to ageing-induced ECM stiffening.
-Evaluate the role of nuclear mechanotransduction pathways during vascular ageing.