Fig. 4

Vessel-associated progenitors unlikely contribute to myofibers in Sdc3 ^−/− muscles. a Uninjured wild type (WT) and Sdc3 ^−/− (S3−/−) TA muscles, immunostained to detect the endothelial cell marker CD31 (green) and nuclei (DAPI, blue) show an increase in capillary density in Sdc3 ^−/− muscles compared to wild type muscles. Images representative of three biological replicates. b Quantification of a. c Flow cytometric analysis reveals increased numbers of Sca1+ cells in Sdc3 ^−/− (S3−/−) muscles compared to wild type (WT) muscles. Gating scheme shown in Additional file 1: Figure S3A-D and F. d, e The numbers of fibro-adipogenic progenitors (FAPs) either in total (d) or expressed as percentage of all live cells (e) in uninjured muscle are comparable between wild type (WT) and syndecan-3 null (S3−/−) muscles. f FACS-isolated Sca1+ cells from wild type (WT) mice and Sdc3 ^−/− (S3−/−) mice transplanted into wild type recipients that were injured with BaCl₂ 4 h prior to transplant immunostained to detect GFP (green) and laminin (red) and stained with DAPI to detect nuclei 3 weeks post-transplantation. GFP staining is not entirely homogenous due to differences in tissue sectioning. Insets identify an interstitial WT donor cell (magnification, left-hand side) and a Sdc3 ^−/− donor cell in the satellite cell niche (magnifications, right-hand side). g Wild type muscle cross sections immunostained to detect laminin (white), syndecan-4 (red), and Sca1 (green) and stained with DAPI to detect nuclei, show that syndecan-4 (Sdc4) is expressed by satellite cells and that Sca1+/Sdc4− cells are interstitial. h FACS-isolated Sca1+/Sdc4− cells from wild type (WT) and Sdc3 ^−/− (S3−/−) muscles were cultured in myoblast growth medium at clonal density for 4 days and scored as myogenic (clones with myotubes) or non-myogenic clones. Scale bars are 100 μm in a, 30 μm in f, and 10 μm in g. Error bars indicate S.E.M. ** = p < 0.01