A system for the surveillance of stem cell fate and function

Cell based therapies represent a promising area of research in regenerative medicine. However, the mechanism by which transplanted cells contribute to bone healing remains unclear. The authors utilized a transgenic mouse strain expressing both the topaz variant of green fluorescent protein under the control of the collagen type I alpha 1 promoter/enhancer sequence ( Col1a1 GFP ) and membrane-bound tomato red constitutively in all cells types ( R26 mTmG ) to decipher how both transplanted and endogenous cells mediate bone healing (1). Calvarial healing was assessed using both parietal and frontal defects and showed that frontal osteoblasts express Col1a1 to a significantly greater degree than parietal osteoblasts. Col1a1 GFP ; R26 mTmG mice were also used to observe the behavior of adipose-derived stromal cells (ASCs), bone marrow-derived mesenchymal stem cells (BM-MSCs), and osteoblasts following transplantation into critical-sized calvarial defects. ASCs significantly increased the rate of bone healing and exhibited both increased survival and Col1a1 expression when compared to BM-MSCs and osteoblasts. These results support the Col1a1 GFP ; R26 mTmG system as a promising technology for the evaluation of stem cell populations in cell-based therapeutics for the purposes of bone healing.