Low oxygen atmosphere facilitates proliferation and maintains undifferentiated state of umbilical cord mesenchymal stem cells in an hypoxia inducible factor-dependent manner.

BACKGROUND AIMS: As we approach the era of mesenchymal stem cell (MSC) application in the medical clinic, the standarization of their culture conditions are of the particular importance. We re-evaluated the influences of oxygens concentration on proliferation, stemness and differentiation of human umbilical cord Wharton Jelly-derived MSCs (WJ-MSCs). METHODS: Primary cultures growing in 21% oxygen were either transferred into 5% O2 or continued to grow under standard 21% oxygen conditions. Cell expansion was estimated by WST1/enzyme-linked immunosorbent assay or cell counting. After 2 or 4 weeks of culture, cell phenotypes were evaluated using microscopic, immunocytochemical, fluorescence-activated cell-sorting and molecular methods. Genes and proteins typical of mesenchymal cells, committed neural cells or more primitive stem/progenitors (Oct4A, Nanog, Rex1, Sox2) and hypoxia inducible factor (HIF)-1α-3α were evaluated. RESULTS: Lowering O2 concentration from 21% to the physiologically relevant 5% level substantially affected cell characteristics, with induction of stemness-related-transcription-factor and stimulation of cell proliferative capacity, with increased colony-forming unit fibroblasts (CFU-F) centers exerting OCT4A, NANOG and HIF-1α and HIF-2α immunoreactivity. Moreover, the spontaneous and time-dependent ability of WJ-MSCs to differentiate into neural lineage under 21% O2 culture was blocked in the reduced oxygen condition. Importantly, treatment with trichostatin A (TSA, a histone deacetylase inhibitor) suppressed HIF-1α and HIF-2α expression, in addition to blockading the cellular effects of reduced oxygen concentration. CONCLUSIONS: A physiologically relevant microenvironment of 5% O2 rejuvenates WJ-MSC culture toward less-differentiated, more primitive and faster-growing phenotypes with involvement of HIF-1α and HIF-2α-mediated and TSA-sensitive chromatin modification mechanisms. These observations add to the understanding of MSC responses to defined culture conditions, which is the most critical issue for adult stem cells translational applications.

Human mesenchymal stem cells in the treatment of neurological diseases.

Here we provide a comprehensive data on the unique features of mesenchymal stem cells (MSCs) which makes them feasible and preferred candidate for cell-based therapy in neurological clinic. From this point of view the most important features of these cells are: (1) availability from autologous sources independently from age of patient; (2) extensive expansion in vitro; (3) immunomodulatory "bystander" function after transplantation in vivo; (4) potentiality to protect, repair or eventually replace impaired or dysfunctional host cells. For complete this last task of functional regeneration of central nervous system, we have to take advantages of MSCs capability for transient, time-locked proliferation, migration to site of injury and their commitment to neuronal differentiation. However, if we are to make progress in the use of MSCs for therapy in the clinic it will be necessary to establish more unified, advanced standards for cells processing in vitro as well as safer and improved procedures for their delivery in vivo.