Primary dermal fibroblasts derived from sdc-1 deficient mice migrate faster and have altered αv integrin function

The goal of this study is to determine whether dermal fibroblasts lacking syndecan-1 (sdc1) show differences in integrin expression and function that could contribute to the delayed skin and corneal wound healing phenotypes seen in sdc-1 null mice. Using primary dermal fibroblasts, we show that after 3 days in culture no differences in alpha-smooth muscle actin were detected but sdc-1 null cells expressed significantly more alpha v and beta 1 integrin than wildtype (wt) cells. Transforming growth factor beta 1 (TGF beta 1) treatment at day 3 increased alpha v- and beta 1-integrin expression in sdc-1 null cells at day 5 whereas wt cells showed increased expression only of alpha v-integrin. Using time-lapse studies, we showed that the sdc-1 null fibroblasts migrate faster than wt fibroblasts, treatment with TGF beta 1 increased these migration differences, and treatment with a TGF beta 1 antagonist caused sdc-1 null fibroblasts to slow down and migrate at the same rate as untreated wt cells. Cell spreading studies on replated fibroblasts showed altered cell spreading and focal adhesion formation on vitronectin and fibronectin-coated surfaces. Additional time lapse studies with beta 1- and alpha v-integrin antibody antagonists, showed that wt fibroblasts expressing sdc-1 had activated integrins on their surface that impeded their migration whereas the null cells expressed alpha v-containing integrins which were less adhesive and enhanced cell migration. Surface expression studies showed increased surface expression of alpha 2 beta 1 and alpha 3 beta 1 on the sdc-1 null fibroblasts compared with wt fibroblasts but no significant differences in surface expression of alpha 5 beta 1, alpha v beta 3, or alpha v beta 5. Taken together, our data indicates that sdc-1 functions in the activation of alpha v-containing integrins and support the hypothesis that impaired wound healing phenotypes seen in sdc-1 null mice could be due to integrin-mediated defects in fibroblast migration after injury.