Mesenchymal stromal cells (MSCs) are promising candidates for tissue engineering and regenerative medicine. The multipotent stem cell component of MSC isolates is able to differentiate into derivatives of the mesodermal lineage including adipocytes, osteocytes, chondrocytes, and myocytes. Many common pathways have been described in the regulation of adipogenesis and osteogenesis. However, stimulation of osteogenesis appears to suppress adipogenesis and vice-versa. Increasing evidence implicates a tight regulation of these processes by reactive oxygen species (ROS). ROS are short-lived oxygen-containing molecules that display high chemical reactivity toward DNA, RNA, proteins, and lipids. Mitochondrial complexes I and III, and the NADPH oxidase isoform NOX4 are major sources of ROS production during MSC differentiation. ROS are thought to interact with several pathways that affect the transcription machinery required for MSC differentiation including the Wnt, Hedgehog, and FOXO signaling cascades. On the other hand, elevated levels of ROS, defined as oxidative stress, lead to arrest of the MSC cell cycle and apoptosis. Tightly regulated levels of ROS are therefore critical for MSC terminal differentiation, although the precise sources, localization, levels and the exact species of ROS implicated remain to be determined. This review provides a detailed overview of the influence of ROS on adipogenic and osteogenic differentiation in MSCs.

Increasing evidence exposes a subpopulation of cancer cells, known as cancer stem cells (CSCs), to be critical for the progression of several human malignancies, including glioblastoma multiforme (GBM). CSCs are highly tumorigenic, capable of self-renewal, and resistant to conventional therapies, and thus considered to be one of the key contributors to disease recurrence. In order to elucidate the poorly understood evolutionary path of tumor recurrence and the role of CSCs in this process, we developed patient-derived xenograft GBM recurrent models induced by anti-glioma chemotherapy, temozolomide (TMZ). In this model, we observed a significant phenotypic shift towards an undifferentiated population. We confirmed these findings in vitro as sorted CD133-negative populations cultured in differentiation-forcing media were found to acquire CD133 expression following chemotherapy treatment. To investigate this phenotypic switch at the single cell level, GSC-specific promoter-based reporter systems were engineered to track changes in the GSC population in real time. We observed the active phenotypic and functional switch of single non-stem glioma cells to a stem-like state and that TMZ therapy significantly increased the rate of single-cell conversions. Importantly, we showed the therapy induced hypoxia inducible factors (HIF) 1α and HIF2α play key roles in allowing non-stem glioma cells to acquire stem-like traits, as the expression of both HIFs increase upon TMZ therapy and knockdown of HIFs expression inhibits the interconversion between non-stem glioma cells and GSCs post-therapy. Based on our results, we propose that anti-glioma chemotherapy promotes the accumulation of HIFs in the GBM cells that induces the formation of therapy-resistant GSCs responsible for recurrence.

Currently the use of non-autologous cell culture media (e.g., animal-derived or allogeneic serum) for clinical applications of mesenchymal stem cells (MSCs) is criticized by regulatory agencies. Autologous platelet-rich plasma (PRP) is proposed as a safer alternative medium supplement for adipose-derived mesenchymal stem cells (AT-MSC) culture. To study its efficiency on cell proliferation, AT-MSCs were cultured for 10 days in media supplemented with different concentrations of autologous non-activated PRP (nPRP) or thrombin-activated PRP (tPRP) (1-60%). AT-MSC proliferation, cell phenotype, multipotency capacity, and chromosome stability were assessed and compared to AT-MSCs expanded in a classical medium supplemented with 10% of fetal bovine serum (FBS). Culture media supplemented with nPRP showed dose-dependent higher AT-MSC proliferation than did FBS or tPRP. Twenty percent nPRP was the most effective concentration to promote cell proliferation. This condition increased 13.9 times greater AT-MSC number in comparison to culture with FBS, without changing the AT-MSC phenotype, differentiation capacity, and chromosome status. We concluded that 20% autologous nPRP is a safe, efficient, and cost-effective supplement for AT-MSC expansion. It should be considered as an alternative to FBS or other nonautologous blood derivatives. It could serve as a potent substitute for the validation of future clinical protocols as it respects good manufacturing practices and regulatory agencies' standards.