TGFß1 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 ß1 (TGFß1) emerged as a specific modifier of age-associated VSM stiffening in vitro. TGFß1 reinforced the mechanical phenotype of arterial aging in VSM cells on multiple time and length scales through clustering of mechanosensitive α5ß1 and αvß3 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 TGFß1 expression, or TGFß1 signal transduction in VSM, may be a useful therapeutic approach to mitigate the pathologic progression of central arterial wall stiffening associated with aging.

Tissue Transglutaminase Modulates Vascular Stiffness and Function Through Crosslinking-Dependent and Crosslinking-Independent Functions.

BACKGROUND: The structural elements of the vascular wall, namely, extracellular matrix and smooth muscle cells (SMCs), contribute to the overall stiffness of the vessel. In this study, we examined the crosslinking-dependent and crosslinking-independent roles of tissue transglutaminase (TG2) in vascular function and stiffness. METHODS AND RESULTS: SMCs were isolated from the aortae of TG2-/- and wild-type (WT) mice. Cell adhesion was examined by using electrical cell-substrate impedance sensing and PicoGreen assay. Cell motility was examined using a Boyden chamber assay. Cell proliferation was examined by electrical cell-substrate impedance sensing and EdU incorporation assays. Cell micromechanics were studied using magnetic torsion cytometry and spontaneous nanobead tracer motions. Aortic mechanics were examined by tensile testing. Vasoreactivity was studied by wire myography. SMCs from TG2-/- mice had delayed adhesion, reduced motility, and accelerated de-adhesion and proliferation rates compared with those from WT. TG2-/- SMCs were stiffer and displayed fewer cytoskeletal remodeling events than WT. Collagen assembly was delayed in TG2-/- SMCs and recovered with adenoviral transduction of TG2. Aortic rings from TG2-/- mice were less stiff than those from WT; stiffness was partly recovered by incubation with guinea pig liver TG2 independent of crosslinking function. TG2-/- rings showed augmented response to phenylephrine-mediated vasoconstriction when compared with WT. In human coronary arteries, vascular media and plaque, high abundance of fibronectin expression, and colocalization with TG2 were observed. CONCLUSIONS: TG2 modulates vascular function/tone by altering SMC contractility independent of its crosslinking function and contributes to vascular stiffness by regulating SMC proliferation and matrix remodeling.