Adult Bone Marrow-derived Mesenchymal Stem Cells Cultured And Differentiate Into Neuron-like Cells By Directional Induction In Vitro

OBJECTIVE: Significant improvement in the understanding of mesenchymal stem cell (HMSC) biology has opened the way to their clinical use. However, concerns regarding the possibility that HMSCs undergo malignant transformation have been raised. We investigated the susceptibility to transformation of human bone marrow (BM)–derived HMSCs at different in vitro culture time points.METHODS: HMSCs were isolated from BM of 10 healthy donors and propagated in vitro until reaching either senescence or passage (P) 25. HMSCs in the senescence phase were closely monitored for 8 to 12 weeks before interrupting the cultures. The genetic characterization of HMSCs was investigated through array-comparative genomic hybridization (array-CGH), conventional karyotyping,and subtelomeric fluorescent in situ hybridization analysis both before and after prolonged culture. HMSCs were tested for the expression of telomerase activity, human telomerase reverse transcriptase (hTERT) transcripts, and alternative lengthening of telomere (ALT) mechanism at different passages.Results: A huge variability in terms of proliferative capacity and HMSCs life span was noted between donors. In eight of 10 donors, HMSCs displayed a progressive decrease in proliferative capacity until reaching senescence. In the remaining two HMSC samples, the cultures were interrupted at P25 to pursue data analysis. Array-CGH and cytogenetic analyses showed that HMSCs expanded in vitro did not show chromosomal abnormalities. Telomerase activity and hTERT transcripts were not expressed in any of the examined cultures and telomeres shortened during the culture period. ALT was not evidenced in the HMSCs tested.Conclusion: BM-derived HMSCs can be safely expanded in vitro and are not susceptible to malignant transformation, thus rendering these cells suitable for cell therapy approaches.