Toxic and DNA damaging effects of a functionalized fullerene in human embryonic lung fibroblasts.

Water-soluble fullerenes have been studied as potential nanovectors and therapeutic agents, but their possible toxicity is of concern. We have studied the effects of F-828, a soluble fullerene [C60] derivative, on diploid human embryonic lung fibroblasts (HELFs) in vitro. F-828 causes complex time-dependent changes in ROS levels. Inhibition of Nox4 activity by plumbagin blocks F-828-dependent ROS elevation. F-828 induces DNA breaks, as measured by the comet assay and γH2AX expression, and the activities of the transcription factors NF-kB and p53 increase. F-828 concentrations>25µM are cytotoxic; cell death occurs by necrosis. Expression levels of TGF-ß, RHOA, RHOC, ROCK1, and SMAD2 increase following exposure to F-828. Our results raise the possibility that fullerene F-828 may induce pulmonary fibrosis in vivo.

Genotoxicity of single-walled carbon nanotubes: in vitro study on human embryonic fibroblast cells.

The effects of single-walled carbon nanotubes on the levels of DNA aberrations, chromosome and genome disorders were studied on human embryonic fibroblasts, their karyotype was analyzed by the spectral karyotyping method. The level of DNA aberrations increased after 3-h exposure to the nanotubes. No appreciable increase in the incidence of aberrant metaphases, micronuclei, and chromosome 1, 6, 8, 11, X, and Y aneuploidy after 24- and 48-h incubation with the nanotubes were detected.

[Risk of genetic transformation of multipotent mesenchymal stromal cells in vitro].

Proof of the efficacy of cell therapy by numerous studies and clinical trials inevitably has raised the question of improving the regulatory framework that governs its use. Particular attention should be paid to the genetic safety of cell preparations. The immune, genetic, and pharmacological modification and expansion of cells in vitro can lead to an undesired effect, which not only has reduced the healing, recovery, and regulatory potential of cell therapy, but also increased the risk of accumulating genetically aberrant cells and the oncogenic transformation of cell preparations. The article has presented the estimation of the parameters of the genetic stability of cultured multipotent mesenchymal stromal cells (MSCs) derived from bone marrow and adipose tissue. The study was conducted using classic methods of genotoxicology, i.e., the individual cells gel-electrophoresis (DNA comets) and the micronucleus test. We described a basic level of DNA damage and the frequency of micronucleus, identified genetically instable cultures, and conducted the comparison of genetic variability of MSCs isolated from different tissues.

[Genetic safety of cellular therapy].

This paper presents the main results of the study on chromosome and genome variability of mesenchymal stem cell cultures from bone marrow and adipose tissue carried out in the Laboratory of Mutagenesis, Research Centre for Medical Genetics, over the last three years. Genome stability was assessed from DNA damage using the DNA comet assay, karyotyping and registration of aneuploidy by the FISH method. We found that DNA damage rate in MSC cultures from bone marrow was 3.9% and 3.8% at the early (2-5) passages and the late (10-15) passages respectively. The cultures were characterized by high dispersion of individual values. Karyotyping showed mosaicism in both types of MSC cultures at the early and late stages of cultivation. The fraction of abnormal cells in some cultures amounted to 80-90%. Evaluation of aneuploidy in interphase cells revealed 1.34% of aneuploid cells (on the average) per one "conventional" chromosome; their overall frequency in the genome amounted to 20-40%. The frequency of aneuploid cells was similar at the early and late passages. Cultures with clones of trisomic and monosomic cells were revealed. The probability of occurrence of abnormal cells may increase by virtue of de novo mutations in the culture and as a result of positive selection of the cells existing in the organism that exhibit a higher reproduction rate in culture. Based on the experimental data on mutational process, selection of mutant cells and clone formation, it is concluded that cytogenetic control of stem cells is necessary to ensure the safety of cellular therapy.

Assessment of DNA damage in human bone marrow cells and multipotent mesenchymal stromal cells.

We carried out a comparative analysis of DNA damage (percentage of DNA in comet tail) and frequencies of comets in apoptotic cells in BM samples and cultures of BM multipotent mesenchymal stromal cells at different terms of culturing (passages 3-11). The levels of DNA damage in mesenchymal stromal cells remained unchanged during culturing (3.5 ± 0.9 and 4.4 ± 1.2%) and did not differ from those in BM cells (3.6 ± 0.8%). In BM samples, 10-28% atypical cells with high level of DNA damage were detected. In mesenchymal stromal cells, 2.8 ± 0.9 and 3.6 ± 1.8% apoptotic cells were detected at early and late passages, respectively.