Fig. 3. MMP function is required for normal branching morphogenesis. Timed-pregnant mice were treated with 100 mg/kg of GM6001 (b,d) or vehicle control (PBS) (a,c) starting at E10.5 for three days. (a,b) Equivalent sections from left lung of embryos treated by sham inhibition (a) or with MMP inhibitor (b), then stained with H and E. Dark boxes indicate the region of epithelial mesenchymal contact presented at higher magnification in c and d. The arrow in c indicates a newly forming branch. Arrowheads in b and d point to loose or poorly organized mesenchyme. Bars, 200 µm (a,b); 50 µm (c,d). Li, liver; Lu, lung; H, heart.