and migration of fibroblasts to the vitronectin- and fibronectin-rich
alveolar matrices are critical processes in wound repair after acute
lung injury. This study was undertaken to determine the mechanism by
which human lung fibroblasts attach and migrate toward provisional
alveolar matrix proteins, and to develop mechanism-based, novel
therapeutic agents designed to specifically inhibit these functions. We
have previously demonstrated urokinase plasminogenactivator receptor
(u-PAR) and a functional fibrinolytic system on these cells. Analysis
of surface integrins reveals expression of the vitronectin receptors
αvβ3, αvβ5, αvβ1, and α8β1. Fibroblast attachment to
vitronectin was inhibited by 50 μg/mL of anti–u-PAR IgG (70%),
monoclonal antibody (mAb) anti-β1 integrin (80%), and mAb
anti-αvβ5 integrin (30%), but not by mAb to αvβ3, α3, and
α5 integrins in the presence of 1 mM Ca++.
These data suggest that u-PAR–integrin interactions play an important
role in fibroblast attachment to provisional alveolar matrix proteins.
Furthermore, a peptide homologous to the u-PAR binding site on integrin
α-chains also blocked cell attachment to vitronectin in a
concentration-dependent manner (70% at 100 μM), while the control
scrambled peptide had no effect. These data suggest that u-PAR
interacts with αvβ1 or α8β1 in mediating fibroblast attachment
to vitronectin. A replication-deficient adenovirus encoding for the
u-PAR binding region of the integrin α-chain was generated, and
adenoviral infection of human lung fibroblasts was optimized.
Adenovirally infected fibroblasts (multiplicity of infection = 500,
48 h) had reduced migration toward vitronectin (50%) and
fibronectin (30%) in a haptotactic migration assay (6 h, 1 mM
Ca++), whereas the migration of cells infected
with a control virus encoding the scrambled peptide was similar to that
seen in uninfected cells. Similarly, adenovirally infected fibroblasts
(multiplicity of infection = 500, 48 h) had reduced attachment
toward vitronectin (50%), fibronectin (30%), and collagen (30%)
compared to control and uninfected cells. Taken together, these data
suggest that u-PAR–integrin interaction(s) modulate fibroblast
attachment and migration toward provisional alveolar matrix proteins.
Integrin α-chain peptide-encoding adenovirus may provide a novel
antiadhesive therapeutic approach for abrogating the fibroproliferative
response after lung injury.