INTRODUCTION: There is increasing interest in the use of adipose-derived mesenchymal stromal cells (ASCs) for wound repair. However, the location of administered ASCs, as well as their migration, engraftment and survival are still poorly defined. Prior to assessing the benefit of ASCs in in vivo models of wound healing, an appropriate tracking system needs to be established to follow administered cells. This study aimed to assess the possibility of in vivo tracking of ASCs labelled with green fluorescent protein (GFP) and firefly luciferase (fLUC).
MATERIALS AND METHODS: ASCs were isolated from rat inguinal adipose tissue and transduced with a dual lentivector to express both GFP and fLUC. In vitro, flow cytometry and bioluminescence imaging (BLI) were performed to detect GFP and fLUC positive cells, respectively. For in vivo tracking, wounds created on the hind paws of rats received either a single injection of ASCs systemically into the tail vein (2x106 ASCs) or locally into each wound (105 ASCs). ASC distribution was followed in animals by BLI 3h and 48h post ASC injection.
RESULTS: In vitro experiments demonstrated that ASCs were successfully transduced to express both GFP and fLUC without influencing their phenotype (CD90+, CD29+, CD31- and CD45-). In vivo, 3h post-injection, ASCs were detected in the lungs of animals treated systemically with a decrease in signal seen from 3h to 48h, but no luminescent signal was detected in the wound. However, locally administered ASCs remained strongly detectable after 48h at the wound site.
CONCLUSIONS: Using a physiological wound repair model we show that GFP/fLUC labelling allowed ASC to be tracked in vivo. However, as the majority of ASCs are filtered out in the lungs, further studies using a model of severe wounds (e.g. ischemia and hyperglycemia) should be performed to determine whether ASC homing is affected by strong inflammatory cues.