Background Peripheral arterial disease (PAD) is highly prevalent and particularly in elders, smokers, diabetics or patients with systemic atherosclerosis. Apart from the surgery and medication, stem cell transplantation offers promising approaches for therapeutic angiogenesis and tissue repair. In this study we try to use in vivo multimodality molecular imaging strategies to investigate adipose tissue-derived mesenchymal stem cells (MSCs) survival, function and relative mechanism.

Method MSCs were cultured from murine adipose tissue from transgenic mice, which carried double reporter genes: firefly luciferase (Fluc) and enhanced green fluorescent protein (eGFP), by collagenase digestion method. Hindlimb ischaemia animal model was created in male nude mice by ligating the proximal and distal femoral artery. MSCs (1×10⁵) along with/without VEGF (0.4 ng) were transplanted into ischaemic hindlimb. The animals were subjected to be imaged by bioluminescence imaging and CT scan. Laser Doppler perfusion imaging (LDPI) were used to show the spatiotemporal images of peripheral tissue blood perfusion. Micro-CT, histological and molecular analysis were tested to confirm the cells' location and angiogenesis anatomically and mechanically. Result The colour-coded index of LDPI was significantly higher in the MSCs-transplanted group than that in the control group from day 3 to 28 post cell transplantation. On day 3 after transplantation, the bioluminescence signals in MSCs with VEGF group were 4.6×10⁶±2.5×10⁵ photons/s/cm²/sr, while in MSCs group were 2.8×10⁶±3.1×10⁵ photons/s/cm²/sr, respectively (p<0.01 vs control). The signals of bioluminescence increased gradually from POD 3 to day 21, which proved survival and proliferation of the MSCs in the host. The group treated with MSCs and VEGF showed higher signals than that injected by MSCs only, which indicated the reinforcement of VEGF. Micro-CT angiography demonstrated more angiogenesis in the hindlimbs of the treated mice on day 21, which were also confirmed by molecular analysis. Histological analysis showed that MSCs therapy recovered vessel density compared with the control group.

Conclusion Bioluminescence fusion with CT scan provides higher detailed 3D imaging for monitoring MSCs in vivo. Angiogenesis activator VEGF might promote MSCs' beneficial function for hindlimb ischaemia therapy.