Molecular imaging reveals skeletal engraftment sites of transplanted bone marrow cells.

Molecular imaging holds great promise for the in vivo study of cell therapy. Our hypothesis was that multimodality molecular imaging can identify the initial skeletal engraftment sites post-bone marrow cell transplantation. Utilizing a standard mouse model of bone marrow (BM) transplantation, we introduced a combined bioluminescence (BLI) and positron emission tomography (PET) imaging reporter gene into mouse bone marrow cells. Bioluminescence imaging was used for monitoring serially the early in vivo BM cell engraftment/expansion every 24 h. Significant cell engraftment/expansion was noted by greatly increased bioluminescence about 1 week posttransplant. Then PET was applied to acquire three-dimensional images of the whole-body in vivo biodistribution of the transplanted cells. To localize cells in the skeleton, PET was followed by computed tomography (CT). Co-registration of PET and CT mapped the sites of BM engraftment. Multiple, discrete BM cell engraftment sites were observed. Taken together, this multimodality approach may be useful for further in vivo characterization of various therapeutic cell types.