[Characterization of cultured murine mesenchymal stem cell line expressing GFP]

We have developed and characterized a murine mesenchymal stem cell line from the bone marrow of transgenic mouse C57BL ubiquitously expressing GFP. Immunostaining analysis revealed the presence of several markers typically found in fibroblasts such as smooth muscle cells actin in the form of stress fibrils and vimentin--the protein of intermediate filaments. These cells maintained capability to differentiate into adipocytes or osteoblasts under appropriate conditions. Karyotypic features include changes in the ploidy level between 2n and 8n and multiple chromosomal aberrations. After six passages 80% of the cell population was aneuploid with chromosomal numbers between 50 and 85 without well defined modal class. Differential G-staining of metaphase spreads showed variability in copy numbers of individual chromosomes and the presence of aberrations such as ectopic associations of non-homologous chromosomes. All analyzed cells contained unique dicentric marker chromosome and some of them also had numerous microchromosomes which might indicate gene amplification. These cells could be useful in the future work directed at the investigation of stem cells spontaneous oncogenic transformation in vivo and in vitro.