In vivo vasculogenic potential of EPCs. Matrigel implants containing cbEPCs and/or HSVSMCs evaluated after one week. (A) H&E staining of implants (×100) containing a combination of cbEPCs (passage 6) and HSVSMCs, (B) only cbEPCs, (C) only HSVSMCs, (D) and Matrigel alone. H&E staining of implants containing both cbEPCs and HSVSMCs evaluated at day 2 (E), day 4 (F), and day 7 (G, ×100; H, ×400) after xenografting. (I-L) Matrigel plug containing cbEPCs and HSVSMCs harvested one week after implantation. (I) Macroscopic view of explanted Matrigel plug. (J) H&E staining showing high-power view of one microvessel containing hematopoietic cells. (K) Immunohistochemical staining at one week with human-specific CD31 antibody (×400) and with (L) α-SMA antibody. All images are representative of implants harvested from 4 different animals. (Black scale bar represents 250 μm; white scale bar, 50 μm.)