Abnormal collagen degradation by CD151-deficient cells. (A) Immunostaining of collagen I to show degradation by MLECs derived from WT or MT1-MMP deficient animals after 24-hour growth on 1 mg/mL rat-tail collagen I. Autofluorescence (blue) was acquired to reveal cell positions. (B) Immunostaining of collagen I to show degradation at 24 hours and 48 hours by WT or CD151 KO MLECs. Nuclei were stained with Hoechst to show the position of the cells. Monochrome images show the masks of the collagen-denuded areas (black) in the same fields. (C) Quantification of total collagen degradation area (left panel: total denuded area/number of cells; mean ± SE) or the average size of the degradation areas (right panel: mean ± SD) from WT and CD151 KO mice. A minimum of 50 cells in 20 or more 63× fields were counted in 2 independent MLEC preparations. *P < .05, Mann-Whitney t test. (D) HUVECs transfected with negative control oligonucleotide or CD151-specific siRNA (left) and MLECs derived from WT or CD151 KO mice (right) were seeded onto DQ-collagen–coated coverslips, fixed, and visualized by fluorescence microscopy.