Chromosomal variability of human mesenchymal stem cells cultured under hypoxic conditions.
Bottom Line: The safe, rapid expansion of hMSCs is critical for their clinical application.Chromosomal aberrations, including structural instability or aneuploidy, were detected in significantly earlier passages under hypoxic conditions than under normoxic culture conditions, suggesting that amplification of hMSCs in a low-oxygen environment facilitated chromosomal instability.In conclusion, we propose that the continuous monitoring of hMSCs will be required before they are used in therapeutic applications in the clinic, especially when cells are cultured under hypoxic conditions.
Affiliation: Department of Pharmacoepidemiology, Graduate School of Medicine and Public Health, Kyoto University, Yoshidakonoecho, Sakyo-ku, Kyoto, Japan.Show MeSH
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Mentions: We compared spontaneous transformations in cells cultured under normal-oxygen (20%) and low-oxygen (5%) conditions. Figure 3A shows aberration-free survival curves for occurrence of spontaneous chromosomal aberrations as an end-point throughout in vitro expansion, which is estimated using the Kaplan–Meier method. In survival analysis, once abnormal karyotypes are detected or follow-up time is ended, the donor becomes not at risk. Under hypoxia, spontaneous transformations were detected in earlier passages than under normoxic conditions, which was statistically significant (log-rank test; P = 0.032). Overall increased risk of spontaneous transformations under hypoxic conditions was estimated at 2.70 (95% CI, 1.01–8.10) compared with normoxic conditions, presented as odds ratios in Table 2. Smoothed hazard modelling for occurrence of chromosomal aberrations illustrated the increased hazard risk after passage 4 in both sets of culture conditions (Fig. 3B). An increased hazard of primary karyotypic abnormality was detected when donors had hMSCs with an initial anomalous karyotype. We found significant effects of PDL and donor age on the risk of spontaneous transformation after controlling for culture conditions. Incremental risk associated with one increase in PDL was estimated at 1.14 (95% CI, 1.04–1.26) and the risk associated with overall expansion was estimated at 18.6 (95% CI, 2.61–158), as presented by the odds ratios in Table 2. Similarly, donor age range of 50s, 60s and 70s elevated the risk of spontaneous transformations compared with donors in their 40s, at 6.59 (95% CI, 0.99–130), 17.3 (3.00–329) and 7.33 (1.09–146), respectively (Table 2). The confidence intervals of estimated odds ratio for donor age were wide because the sample size was limited in this research.
Affiliation: Department of Pharmacoepidemiology, Graduate School of Medicine and Public Health, Kyoto University, Yoshidakonoecho, Sakyo-ku, Kyoto, Japan.