Figure 1.

sFRP-1 induces HUVEC spreading on extracellular matrix and promotes HUVEC cell spreading to collagen type I through α2β1-integrin. a: HUVECs were allowed to spread on polylysine (PL), type I collagen (Coll I), type IV collagen (Coll IV), or laminin (LM) in the absence or presence of rb sFRP-1 in serum-free medium for 2 hours. The percentage of spread cells were scored as described in the Materials and Methods section. Cell surface area was quantified in adherent HUVECs after staining by rhodamine-phalloidin Treatments were performed in triplicate, and results are expressed as mean percent spreading ± SD. *P < 0.05 relative to controls. b: F-actin (red fluorescence) and focal adhesion plaque (green fluorescence) distributions were detected in adherent HUVECs after staining with rhodamine-phalloidin or vinculin labeling in the absence (control) (□) or in the presence (▪) of recombinant bovine sFRP-1 (+rb sFRP-1). c: Spreading assays of HUVECs were performed in the presence of function-blocking antibodies against β1, α2β1, and αvβ3 integrins on wells coated with type I collagen. A mouse IgG served as control. Cells were preincubated for 15 minutes before plating with function-blocking mAbs at a concentration of 4 μg/ml in the absence (□) or presence (▪) of recombinant bovine sFRP-1. Spreading was quantified by counting the number of spread cells per field as described in the Materials and Methods section (×20 objective). Results are expressed as mean spreading as percentage of control ± SD. *P < 0.05 relative to controls.