Mesenchymal stem cells immortalization's and state-of-art: a systematic review and meta-analysis

Abstract Background The immortalization of mesenchymal stem cells (MSCs) allows them to avoid senescence and be cultured through limitless cell passages. Thus, several experimental strategies, such as retrovirus-mediated gene transfer or viral oncogenesis, have been applied for the immortalization of MSCs. The aim was to identifier the most commonly used methodologies and their particularities for the immortalization of human and animal MSCs. Methods The search was conducted in June 2019 and developed in SCOPUS, PUBMED, and SCIENCE DIRECT. Statistical analysis was performed, obtaining the values of total n, mean and standard deviation, confidence interval (CI), and percentage (frequency) for all the predictors. Results The most used immortalization methodology was viral transfection, being the most common immortalized cell type was the bone marrow-derived MSC, and the most used gene for immortalizing both human and animal MSCs was hTERT (39.3%) and SV40T (54.5%). Among the articles analyzed in this review, only 39.3% and 36.4% of human and animal MSCs immortalization protocols, respectively, underwent the tumorigenicity test. Conclusions The virus-mediated gene transfection was observed as the most used and established technique. The insertion of the hTERT gene is still the most used gene for cell immortalization, suggesting that the maintenance of telomerase is efficient for maintaining cell proliferation and bypassing cell senescence. The review concluded that the tumorigenicity tests should become mandatory in order to safely use the immortalized MSCs for translation.