Intravital monitoring of EGFP-hMSCs in a tissue-engineered vessel model. Fibronectin-collagen constructs with EGFP-hMSCs alone (A) or EGFP-hMSCs with DsRed-HUVECs (B-G) were implanted into cranial windows of SCID mice. Images were taken at different time points with multiphoton laser scanning microscopy (MPLSM) (B, day 7; C,D, day 19; E,F, day 31; G, day 83). Green indicates human mesenchymal stem cells expressing EGFP (A-G); red, HUVECs expressing DsRed-express fluorescent protein (B-E,G); and red, functional blood vessels contrast-enhanced by rhodamine-dextran (D,F). Scale bars represent (A,B,G) 100 μm; (C-F) 50 μm.