ABSTRACT
Mesenchymal stem cells (MSCs) can differentiate into osteogenic, adipogenic, chondrogenic, myocardial, or neural lineages when exposed to specific stimuli, making them attractive for tissue repair and regeneration. We have used reporter gene-based imaging technology to track MSC transplantation or implantation in vivo. However, the effects of lentiviral transduction with the fluc-mrfp-ttk triple-fusion vector on the transcriptional profiles of MSCs remain unknown. In this study, gene expression differences between wild-type and transduced hMSCs were evaluated using an oligonucleotide human microarray. Significance Analysis of Microarray identified differential genes with high accuracy; RT-PCR validated the microarray results. Annotation analysis showed that transduced hMSCs upregulated cell differentiation and antiapoptosis genes while downregulating cell cycle, proliferation genes. Despite transcriptional changes associated with bone and cartilage remodeling, their random pattern indicates no systematic change of crucial genes that are associated with osteogenic, adipogenic, or chondrogenic differentiation. This correlates with the experimental results that lentiviral transduction did not cause the transduced MSCs to lose their basic stem cell identity as demonstrated by osteogenic, chondrogenic, and adipogenic differentiation assays with both transduced and wild-type MSCs, although a certain degree of alterations occurred. Histological analysis demonstrated osteogenic differentiation in MSC-loaded ceramic cubes in vivo. In conclusion, transduction of reporter genes into MSCs preserved the basic properties of stem cells while enabling noninvasive imaging in living animals to study the biodistribution and other biological activities of the cells.
Subject(s)
Gene Expression Profiling , Genes, Reporter , Mesenchymal Stem Cells/metabolism , Transcription, Genetic , Transduction, Genetic , Whole Body Imaging , Adipogenesis , Animals , Biological Assay , Ceramics , Gene Regulatory Networks , Humans , Luciferases/metabolism , Luminescent Proteins/metabolism , Mesenchymal Stem Cell Transplantation , Mesenchymal Stem Cells/cytology , Mice , Oligonucleotide Array Sequence Analysis , Pluripotent Stem Cells/cytology , Pluripotent Stem Cells/metabolism , Prosthesis Implantation , Software , Thymidine Kinase/metabolism , Red Fluorescent ProteinABSTRACT
A slat collimator in single photon emission computed tomography consists of a set of parallel slats. As the collimator spins, the detector measures a one-dimensional projection data set. A complete data set can be obtained by rotating the detector/collimator assembly around the object (patient) while the collimator spins continuously. The measured projection data are assumed to be weighted planar integrals of the object. This paper describes the development of an approximate three-dimensional image reconstruction algorithm for a rotating/spinning slat collimator. This algorithm is in filtered backprojection form. Computer simulations were performed to verify the effectiveness of the algorithm.
