Nuclear redox control of stem cell ageing

Mesenchymal stem cells (MSCs) have emerged as an important tool that can be used for drug screening, disease modeling and tissue regeneration thanks to their easy preparation, differentiation potential and immunomodulatory activity. A redox imbalance, due to extensive culture of stem cells in vitro prior to clinical use, can lead to oxidative stress. However, oxidative stress is known to play an important role in modulating different stem cells properties, such as self-renewal, proliferation, differentiation and senescence. A specific source of reactive oxygen species, the NADPH oxidase isoform 4 (Nox4), can localize also into the nuclei where it can have an impact on the regulation of crucial stemness-related genes. Moreover, the accumulation in human MSCs’ nuclei of the nuclear lamina precursor, prelamin A, gives rise to a premature aging phenotype that ultimately causes reduced functionality of these cells in vivo. The aim of the study was to investigate the aging process occurring during in vitro expansion of human fetal MSCs, obtained from amniotic fluid at similar gestational age. This process is certainly influenced by the oxidative stress exposure implied in extensive culture, but could be also donor dependent. The analysis of 15 AFSC samples allowed to classify them in groups with different levels of stemness properties evident even since the first passages in culture. In summary, the expression of Oct-4, a pluripotency gene, and proliferation rate are inversely correlated to the presence of the nuclear form of Nox4, the content of reactive oxygen species, DNA damage signs and the onset of senescence and premature aging markers, including accumulation of prelamin A, p21 and p16. Indeed, coimmunoprecipitation experiments demonstrated an interaction between prelamin A and Nox4, suggesting an interplay of these proteins in modulating the maintenance of stemness properties.