Integrin αvβ3 Mediates Elastin Peptide‑Induced VSMC Phenotypic Switching via FAK‑Src‑YAP/TAZ Signaling

Hypothesis

Elastin-derived peptides generated during arterial wall degradation act as endogenous ligands for integrin αvβ3 on vascular smooth muscle cells (VSMCs), activating focal adhesion kinase (FAK)-Src signaling that drives YAP/TAZ nuclear translocation and suppresses myocardin‑dependent contractile gene expression, thereby promoting a pro‑calcific, osteochondrogenic phenotype.

Mechanistic Rationale

• Degraded elastin releases bioactive peptides that have been shown to induce VSMC dedifferentiation and MMP‑2 activation 1.
• These peptides can bind integrin αvβ3, a receptor known to sense extracellular matrix rigidity and to transduce mechanical cues via FAK‑Src 4.
• Integrin αvβ3‑FAK‑Src signaling promotes YAP/TAZ nuclear accumulation, which cooperates with TGF‑β‑Smad signaling to upregulate Runx2 and other osteochondrogenic markers 2.
• Simultaneously, YAP/TAZ activation represses myocardin‑SRF transcription, reducing smoothelin and SM-MHC expression, locking VSMCs in a synthetic state.
• This creates a positive feedback loop: synthetic VSMCs secrete more matrix metalloproteinases, further degrading elastin and generating more peptide ligands.

Testable Predictions

1. In vitro: Adding elastin peptides to cultured VSMCs will increase integrin αvβ3 phosphorylation, FAK‑Src activation, and nuclear YAP/TAZ; these effects will be blocked by an αvβ3‑specific antagonist or siRNA knockdown.
2. Ex vivo: Aortic rings from aged or CKD mice treated with elastin peptides will show enhanced VSMC calcification (Alizarin Red) and reduced contractile marker expression; calcification will be attenuated by αvβ3 inhibition.
3. In vivo: CKD mice receiving an integrin αvβ3 blocker (e.g., cilengitide) will exhibit lower arterial pulse wave velocity, less medial calcification, and higher smoothelin/SM-MHC levels despite ongoing elastin degradation, compared with vehicle controls.
4. Biomarker: Plasma levels of elastin-derived peptides will correlate positively with circulating active YAP (nuclear YAP in isolated VSMCs) and inversely with arterial compliance in human cohorts.

Experimental Approach

• Cell culture: Human aortic VSMCs treated with recombinant elastin peptides (e.g., VGVAPG) ± αvβ3 antagonist (cilengitide) or FAK inhibitor (PF‑573228); assess p‑FAK, p‑Src, nuclear YAP/TAZ (immunofluorescence, Western blot), Runx2, smoothelin.
• Mechanistic rescue: Overexpress myocardin or use YAP/TAZ inhibitors (verteporfin) to determine if they are downstream of integrin signaling.
• Animal model: Adenine‑induced CKD mice; administer elastin peptides via osmotic pump; treat groups with vehicle, αvβ3 blocker, or AGE breaker (alagebrium) for 8 weeks; measure PWV, histology (Von Kossa, elastin staining), VSMC phenotype markers.
• Human relevance: Collect plasma from CKD patients; quantify elastin peptides (ELISA), soluble YAP/Taz, and correlate with carotid‑femoral PWV.

Potential Pitfalls and Alternatives

• If elastin peptides do not engage integrin αvβ3, they may act via other receptors (e.g., TLRs); hypothesis would be falsified.
• Compensatory integrin subunits could mask effects; use combined αvβ3 and α5β1 knockdown.
• Off‑target effects of pharmacological blockers; validate with genetic approaches (CRISPR knockout of ITGAV or ITGB3 in VSMCs).

This hypothesis integrates the active elastin‑driven remodeling paradigm with mechanotransduction via integrin αvβ3/YAP‑TAZ, offering a precise, druggable node to break the vicious cycle of arterial stiffening and calcification.