Toward an ideal animal model to trace donor cell fates after stem cell therapy: production of stably labeled multipotent mesenchymal stem cells from bone marrow of transgenic pigs harboring enhanced green fluorescence protein gene.

The discovery of postnatal mesenchymal stem cells (MSC) with their general multipotentiality has fueled much interest in the development of cell-based therapies. Proper identification of transplanted MSC is crucial for evaluating donor cell distribution, differentiation, and migration. Lack of an efficient marker of transplanted MSC has precluded our understanding of MSC-related regenerative studies, especially in large animal models such as pigs. In the present study, we produced transgenic pigs harboring an enhanced green fluorescent protein (EGFP) gene. The pigs provide a reliable and reproducible source for obtaining stable EGFP-labeled MSC, which is very useful for donor cell tracking after transplantation. The undifferentiated EGFP-tagged MSC expressed a greater quantity of EGFP while maintaining MSC multipotentiality. These cells exhibited homogeneous surface epitopes and possessed classic trilineage differentiation potential into osteogenic, adipogenic, and chondrogenic lineages, with robust EGFP expression maintained in all differentiated progeny. Injection of donor MSC can dramatically increase the thickness of infarcted myocardium and improve cardiac function in mice. Moreover, the MSC, with their strong EGFP expression, can be easily distinguished from the background autofluorescence in myocardial infarcts. We demonstrated an efficient, effective, and easy way to identify MSC after long-term culture and transplantation. With the transgenic model, we were able to obtain stem or progenitor cells in earlier passages compared with the transfection of traceable markers into established MSC. Because the integration site of the transgene was the same for all cells, we lessened the potential for positional effects and the heterogeneity of the stem cells. The EGFP-transgenic pigs may serve as useful biomedical and agricultural models of somatic stem cell biology.

Isolation of therapeutically functional mouse bone marrow mesenchymal stem cells within 3 h by an effective single-step plastic-adherent method.

OBJECTIVES: Isolation of mouse mesenchymal stem cells (mMSCs), by the approach of plastic adherence, has been difficult due to persistent contamination by haematopoietic cells (HCs); we have observed that this contamination was due to engagement between HCs and mMSCs. The HCs can be lifted together with the mMSCs despite their insensitivity to trypsin digestion. Herein, we provide a single-step procedure to rapidly segregate mMSCs from HC contaminants using transient lower-density plastic adherence (tLDA). MATERIALS AND METHODS: The tLDA was performed by replating bone marrow adherent cells at lower density (1.25 x 10(4) cells/cm(2)) than usual, allowing for transient adherence of no more than 3 h, followed by trypsin digestion. tLDA-isolated cells were evaluated by immunophenotyping, multi-differentiation potentials, immunosuppressive properties, and therapeutic potential as demonstrated by symptoms of osteoporosis. RESULTS: The single-step tLDA method can effectively eliminate the persistent HC contaminants; tLDA-isolated cells were phenotypically equivalent to those reported as mMSCs. The isolated cells possessed classic tri-lineage differentiation potential into osteogenic, adipogenic and chondrogenic lineages and had immunosuppressive properties. After intravenous transplantation, they migrated into the allogeneic bone marrow and rescued hosts from osteoporosis symptoms, demonstrating their therapeutic potential. CONCLUSIONS: We have developed a simple and economical method that effectively isolates HC-free, therapeutically functional mMSCs from bone marrow cell adherent cultures. These cells are suitable for various mechanistic and therapeutic studies in the mouse model.