Vessel structures stained for human calponin in tissue constructs comprised of (A) 5 mg/mL fibrin, (B) 10 mg/mL fibrin, and (C) 15 mg/mL fibrin with either MSCs alone (O) or HUVECs+MSCs (•). The same data are also represented for (D) MSCs only and (E) HUVECs+MSCs in 5 (O), 10 (•), and 15 mg/mL (□) fibrin gels at days 3, 7, and 21. In panel (A), indicates a statistically significant (p < 0.05) difference between both conditions at day 21. For panels (D and E), there is a statistically significant difference (p < 0.05) between the 5 mg/mL fibrin-based implants and the other two concentrations at day 21. (F) Representative image on day 21 in an implant comprised of 5 mg/mL fibrin and both cell types; arrows identify calponin-stained vessels. Color images available online at www.liebertonline.com/tea.