Fig. 2.

Effect of serum and growth factor-reduced Matrigel (GFR-MG) coating on formation of striated human muscle fibers 14 days after shift to differentiation medium (DM) with the indicated level of serum. Differentiation was characterized by immunofluorescence for sarcomeric α-actinin (green) and Hoechst nuclear stain (blue). A: few fibers were seen in samples cultured on an uncoated surface in 8% equine serum DM. B: few fibers were present in samples cultured on an uncoated surface in 2% equine serum; however, myofibers were longer than those cultured on an uncoated surface in 8% equine serum. C: fibers were more prevalent and robust on surfaces coated with 100 μg/ml GFR-MG in 8% equine serum DM; some cell debris was also present (*), and a few striations were present (arrows). D: robust, striated fibers were seen in HSkM attached to GFR-MG-coated surfaces and differentiated in 2% equine serum-supplemented DM (arrows). Magnification ×20.