Studies in adipose-derived stromal cells: Migration and participation in repair of cranial injury after systemic injection

Background: Adipose-derived stromal cells are a multipotent cell type with the ability to undergo osteogenic differentiation. The authors sought to examine whether systemically administered adipose-derived stromal cells would migrate to and heal surgically created defects of the mouse cranial skeleton. Methods: Mouse adipose-derived stromal cells were harvested from luciferase-positive transgenic mice; human adipose-derived stromal cells were harvested from human lipoaspirate and labeled with luciferase and green fluorescent protein. A 4-mm calvarial defect (critical sized) was made in the mouse parietal bone; skin incisions alone were used as a control (n = 5 per group). Adipose-derived stromal cells were injected intravenously (200,000 cells per animal) and compared with saline injection only. Methods of analyses included micro-computed tomographic scanning, in vivo imaging system detection of luciferase activity, and standard histology. Results: Migration of adipose-derived stromal cells to calvarial defect sites was confirmed by accumulation of luciferase activity and green fluorescent protein stain as early as 4 days and persisting up to 4 weeks. Little activity was observed among control groups. Intravenous administration of either mouse or human adipose-derived stromal cells resulted in histologic evidence of bone formation within the defect site, in comparison with an absence of bone among control defects. By micro-computed tomographic analysis, human but not mouse adipose-derived stromal cells stimulated significant osseous healing. Conclusions: Intravenously administered adipose-derived stromal cells migrate to sites of calvarial injury. Thereafter, intravenous human adipose-derived stromal cells contribute to bony calvarial repair. Intravenous administration of adipose-derived stromal cells may be an effective delivery method for future efforts in skeletal regeneration.