Differential effects of soluble and immobilized fibronectins on aortic endothelial cell proliferation and attachment

Smad3 deficiency ameliorates experimental obliterative bronchiolitis in a heterotopic tracheal transplantation model

Chronic allograft rejection manifested as obliterative bronchiolitis (OB) remains the single greatest impediment to long-term survival after lung transplantation. Transforming growth factor-beta1 (TGF-beta1) has been implicated in the tissue remodeling response associated with OB. Therefore, its intracellular signal transducer, Smad3, is a prime target of investigation. Herein, we examine the role of TGF-beta1, through Smad3, in the development of OB using heterotopic tracheal transplantation in wild-type and Smad3-null mice. TGF-beta1 was detectable within infiltrating mononuclear cells early after transplantation. Later it was detected in fibroblasts and in the connective tissue accumulating within the lumen and the airway wall of the transplanted allografts. Connective tissue growth factor had a similar time and tissue distribution. Nuclear detection of Smad3 and phosphorylated Smads within intraluminal fibroblasts coincided with increased intraluminal deposition of fibronectin and collagen. When transplanted into Smad3-null mice, allografts failed to organize the intraluminal exudates despite fibroblast accumulation and showed reduced fibronectin and collagen deposition. In culture, Smad3-deficient fibroblasts expressed reduced fibronectin in response to TGF-beta1 compared to wild-type cells. Together, these studies suggest that the TGF-beta signal transducer, Smad3, is required for the development of experimental OB in transplanted tracheas.

Fibronectin enhances early shear stress resistance of seeded adult human venous endothelial cells

An in vitro parallel plate perfusion chamber was used to study the shear stress resistance of seeded adult human saphenous vein endothelial cells (AHSVECs) on glass surfaces coated with different substrates. Endothelial cells were seeded onto glass slides precoated with these substrates and then exposed to pulsatile flow with an average shear stress of 8 dyn/cm2 for 1 hr. After AHSVEC attachment periods of 15 min, 1 hr, and 2 hr, flow dislodged all but 1.4, 30.4, and 72.2%, respectively, of cells that had been seeded onto 1% gelatin. Control slides that were not exposed to flow retained 12.9% (P less than 0.03), 49.8% (NS), and 95.2% (NS) of seeded cells. Precoating the slides with 10 micrograms/ml fibronectin resulted in 69.4, 89.5, and 97.7% of cells remaining after flow, compared with 6.4% (P less than 0.03), 53.7% (NS), and 93.3% (NS), respectively, when using matched slides coated with 1% gelatin. Results with 20% fetal bovine serum as the substrate were not statistically different from those obtained with 1% gelatin. We conclude that fibronectin enhances the early attachment of AHSVECs to artificial surfaces and is, therefore, potentially useful for increasing attached cell yields on arterial prostheses prepared with immediate cell seeding techniques.