Abstract 48: Age-associated Imbalance of Vasorin/TGF-β1 Signaling in VSMC Facilitates Collagen Production

Collagen deposition, a hallmark of arterial aging that resembles post-injury arterial restenosis, is perpetrated by angiotensin II (Ang II) signaling in arterial wall. Collagen aggregation at sites of arterial injury is regulated by the coordinated signaling of pro-fibrotic TGF-β1 and anti-fibrotic vasorin within VSMCs. The Ang II/TGF-β1/vasorin signaling relationship within VSMCs with aging, however, remains unknown. In vivo studies in old vs. young FXBN rats show that aortic transcription and translation of vasorin markedly decrease with aging. In vitro studies in VSMCs isolated from old vs. young aortae. Ang II-associated reduction of vasorin protein abundance in young VSMCs and age-associated changes in vasorin protein levels are reversed by the AT1 antagonist, Losartan (Los) (Figure). Dual immunolabeling and co-immunoprecipitation demonstrate that the co-incidence and physical interaction of vasorin and TGF-β1 within VSMCs are significantly decreased with aging. Importantly, exposure of young VSMCs to Ang II that increases p-SMAD2/3 and collagen type I production, mimicking old cells, and this effect is abolished or substantially mitigated by Los treatment, overexpression of ectopic vasorin, or exogenous recombinant human-vasorin protein. In contrast, exposure of old VSMCs to Los decreases p-SMAD2/3 and collagen type I production.Thus, an imbalance of the Ang II/TGF-β1/vasorin signaling cascade, a feature of the aged arterial wall, enhances the collagen production by VSMCs. Maintaining this signaling balance is a novel measure to retard adverse extracellular matrix remodeling, a determinant of arterial stiffening with aging. (MW and GP co-first authors)