title: Imaging early stage osteogenic differentiation of mesenchymal stem cells.
abstract: Stem cells, such as mesenchymal stem cells (MSCs), contribute to bone fracture repair if they are delivered to the injury site. However, it is difficult to assess the retention and differentiation of these cells after implantation. Current options for non-invasively tracking the transplanted stem cells are limited. Cell-based therapies using MSCs would benefit greatly through the use of an imaging methodology that allows cells to be tracked in vivo and in a timely fashion. In this study, we implemented an in vivo imaging methodology to specifically track early events such as differentiation of implanted human MSCs (hMSCs). This system uses the collagen type 1 (Col1α1) promoter to drive expression of firefly luciferase (luc) in addition to a constitutively active promoter to drive the expression of green fluorescent protein (GFP). The resulting dual-promoter reporter gene system provides the opportunity for osteogenic differentiation-specific luc expression for in vivo imaging and constitutive expression of GFP for cell sorting. The function of this dual-promoter reporter gene was validated both in vitro and in vivo. In addition, the ability of this dual-promoter reporter system to image an early event of osteogenic differentiation of hMSCs was demonstrated in a murine segmental bone defect model in which reporter-labeled hMSCs were seeded into an alginate hydrogel scaffold and implanted directly into the defect. Bioluminescence imaging (BLI) was performed to visualize the turn-on of Col1α1 upon osteogenic differentiation and followed by X-ray imaging to assess the healing process for correlation with histological analyses.
authors: Department of Radiology, University Hospitals Case Medical Center, Cleveland, Ohio 44016, USA.
authors: David J
authors: DJ
authors: Corn
authors: Yunhui
authors: Y
authors: Kim
authors: Melissa D
authors: MD
authors: Krebs
authors: Troy
authors: T
authors: Mounts
authors: Joseph
authors: J
authors: Molter
authors: Stanton
authors: S
authors: Gerson
authors: Eben
authors: E
authors: Alsberg
authors: James E
authors: JE
authors: Dennis
authors: Zhenghong
authors: Z
authors: Lee
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D024042:Collagen Type I / Q000235:genetics*; D000090602:Collagen Type I, alpha 1 Chain; D015870:Gene Expression; D017930:Genes, Reporter; D006801:Humans; D049409:Luciferases, Firefly / Q000235:genetics / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000502:physiology*; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010012:Osteogenesis; D011401:Promoter Regions, Genetic; D051381:Rats
chemical_list: D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D049409:Luciferases, Firefly