title: Human bone marrow derived mesenchymal stem cells do not undergo transformation after long-term in vitro culture and do not exhibit telomere maintenance mechanisms.
abstract: Significant improvement in the understanding of mesenchymal stem cell (MSC) biology has opened the way to their clinical use. However, concerns regarding the possibility that MSCs undergo malignant transformation have been raised. We investigated the susceptibility to transformation of human bone marrow (BM)-derived MSCs at different in vitro culture time points. MSCs were isolated from BM of 10 healthy donors and propagated in vitro until reaching either senescence or passage (P) 25. MSCs in the senescence phase were closely monitored for 8 to 12 weeks before interrupting the cultures. The genetic characterization of MSCs was investigated through array-comparative genomic hybridization (array-CGH), conventional karyotyping, and subtelomeric fluorescent in situ hybridization analysis both before and after prolonged culture. MSCs were tested for the expression of telomerase activity, human telomerase reverse transcriptase (hTERT) transcripts, and alternative lengthening of telomere (ALT) mechanism at different passages. A huge variability in terms of proliferative capacity and MSCs life span was noted between donors. In eight of 10 donors, MSCs displayed a progressive decrease in proliferative capacity until reaching senescence. In the remaining two MSC samples, the cultures were interrupted at P25 to pursue data analysis. Array-CGH and cytogenetic analyses showed that MSCs 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 MSCs tested. BM-derived MSCs can be safely expanded in vitro and are not susceptible to malignant transformation, thus rendering these cells suitable for cell therapy approaches.
authors.affiliation: Oncoematologia Pediatrica , Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, Università di Pavia, Pavia, Italy. mebernardo@gmail.com
authors.forename: Maria Ester
authors.initials: ME
authors.lastname: Bernardo
authors.forename: Nadia
authors.initials: N
authors.lastname: Zaffaroni
authors.forename: Francesca
authors.initials: F
authors.lastname: Novara
authors.forename: Angela Maria
authors.initials: AM
authors.lastname: Cometa
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Avanzini
authors.forename: Antonia
authors.initials: A
authors.lastname: Moretta
authors.forename: Daniela
authors.initials: D
authors.lastname: Montagna
authors.forename: Rita
authors.initials: R
authors.lastname: Maccario
authors.forename: Raffaella
authors.initials: R
authors.lastname: Villa
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Daidone
authors.forename: Orsetta
authors.initials: O
authors.lastname: Zuffardi
authors.forename: Franco
authors.initials: F
authors.lastname: Locatelli
mesh_terms: D001854:Bone Marrow Cells / Q000473:pathology* / Q000502:physiology / Q000648:ultrastructure; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000473:pathology* / Q000648:ultrastructure; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D016158:Genes, p53; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D059630:Mesenchymal Stem Cells / Q000473:pathology* / Q000502:physiology / Q000648:ultrastructure; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D019098:Telomerase / Q000096:biosynthesis / Q000235:genetics; D016615:Telomere / Q000235:genetics* / Q000378:metabolism; D013997:Time Factors
chemical_list: D012333:RNA, Messenger; C509186:TERT protein, human; D019098:Telomerase