TGF beta 1 reinforces arterial aging in the vascular smooth muscle cell through a long-range regulation of the cytoskeletal stiffness

Here we report exquisitely distinct material properties of primary vascular smooth muscle (VSM) cells isolated from the thoracic aorta of adult (8 months) vs. aged (30 months) F344XBN rats. Individual VSM cells derived from the aged animals showed a tense internal network of the actin cytoskeleton (CSK), exhibiting increased stiffness (elastic) and frictional (loss) moduli than those derived from the adult animals over a wide frequency range of the imposed oscillatory deformation. This discrete mechanical response was long-lived in culture and persistent across a physiological range of matrix rigidity. Strikingly, the pro-fibrotic transforming growth factor beta 1 (TGF beta 1) emerged as a specific modifier of age-associated VSM stiffening in vitro. TGF beta 1 reinforced the mechanical phenotype of arterial aging in VSM cells on multiple time and length scales through clustering of mechanosensitive alpha(5)beta(1) and alpha(v)beta(3) integrins. Taken together, these studies identify a novel nodal point for the long-range regulation of VSM stiffness and serve as a proof-of-concept that the broad-based inhibition of TGF beta 1 expression, or TGF beta 1 signal transduction in VSM, may be a useful therapeutic approach to mitigate the pathologic progression of central arterial wall stiffening associated with aging

Reduced vasorin enhances angiotensin II signaling within the aging arterial wall

The glycosylated protein vasorin physically interacts with the transforming growth factor-beta1 (TGF-β1) and functionally attenuates its fibrogenic signaling in the vascular smooth muscle cells (VSMCs) of the arterial wall. Angiotensin II (Ang II) amplifies TGF-β1 activation in the VSMCs of the arterial wall with aging. In this study, we hypothesized that a reduced expression of the protein vasorin plays a contributory role in magnifying Ang II-associated fibrogenic signaling in the VSMCs of the arterial wall with aging. The current study shows that vasorin mRNA and protein expression were significantly decreased both in aortic wall and VSMCs from old (30 mo) vs. young (8 mo) FXBN rats. Exposing young VSMCs to Ang II reduced vasorin protein expression to the levels of old untreated cells while treating old VSMCs with the Ang II type AT1 receptor antagonist Losartan upregulated vasorin protein expression up to the levels of young. The physical interaction between vasorin and TGF-β1 was significantly decreased in old vs. young VSMCs. Further, exposing young VSMCs to Ang II increased the levels of matrix metalloproteinase type II (MMP-2) activation and TGF-β1 downstream molecules p-SMAD-2/3 and collagen type I production up to the levels of old untreated VSMCs, and these effects were substantially inhibited by overexpressing vasorin. Administration of Ang II to young rats (8 mo) for 28 days via an osmotic minipump markedly reduced the expression of vasorin. Importantly, vasorin protein was effectively cleaved by activated MMP-2 both in vitro and in vivo. Administration of the MMP inhibitor, PD 166793, for 6 mo to young adult (18 mo) via a daily gavage markedly increased levels of vasorin in the aortic wall. Thus, reduced vasorin amplifies Ang II profibrotic signaling via an activation of MMP-2 in VSMCs within the aging arterial wall