Hypoxia increases Sca-1/CD44 co-expression in murine mesenchymal stem cells and enhances their adipogenic differentiation potential

Abstract

Mesenchymal stem cells (MSCs) are usually cultured under normoxic conditions (21% oxygen). However, in vivo, the physiological "niches" for MSCs have a much lower oxygen tension. Because of their plasticity, stem cells are particularly sensitive to their environments, and oxygen tension is one developmentally important stimulus in stem cell biology and plays a role in the intricate balance between cellular proliferation and commitment towards differentiation. Therefore, we investigated here the effect of hypoxia (2% oxygen) on murine adipose tissue (AT) MSC proliferation and adipogenic differentiation. AT cells were obtained from the omental fat and AT-MSCs were selected for their ability to attach to the plastic dishes, and were grown under normoxic and hypoxic conditions. Prior exposure of MSCs to hypoxia led to a significant reduction of ex vivo expansion time, with significantly increased numbers of Sca-1(+) as well as Sca-1(+)/CD44(+)double-positive cells. Under low oxygen culture conditions, the AT-MSC number markedly increased and their adipogenic differentiation potential was reduced. Notably, the hypoxia-mediated inhibition of adipogenic differentiation was reversible: AT-MSCs pre-exposed to hypoxia when switched to normoxic conditions exhibited significantly higher adipogenic differentiation capacity compared to their pre-exposed normoxic-cultured counterparts. Accordingly, the expression of adipocyte-specific genes, peroxisome proliferator activated receptor gamma (Ppargamma), lipoprotein lipase (Lpl) and fatty acid binding protein 4 (Fabp4) were significantly enhanced in hypoxia pre-exposed AT-MSCs. In conclusion, pre-culturing MSCs under hypoxic culture conditions may represent a strategy to enhance MSC production, enrichment and adipogenic differentiation.

The Alliance of Mesenchymal Stem Cells, Bone, and Diabetes

“…Oxygen tension within the marrow microenvironment is physiologically lower than other tissues and the diabetes status may further alter cellular homeostasis. Indeed, some authors have shown reduced differentiation of MSC toward either adipose or osteoblast phenotype [202, 203], while others suggested an increased differentiation of MSC under hypoxia conditions [204, 205]. Finally, hyperglycemia-induced acidosis may enhance bone resorption and impair bone quality [128].…”

Adipose tissue oxygen tension

“…However, contrasting results have also been reported. Preexposure of adipose tissue-derived MSCs to hypoxia (2% O 2 ) increased their adipogenic potential [62,63], and 8% O 2 accelerated bone marrow-derived MSC differentiation [64]. Taken together, extremely low PO 2 seems to increase proliferation but no consensus has been reached at the moment regarding its effect on differentiation towards the adipogenic lineage.…”

Heterogeneity of adipose tissue in development and metabolic function

“…In 1895, Hammar posited that adipocytes arise from undifferentiated stem cells of a primitive mesenchymal type (Hammar, 1895). Since then, the ability of mesenchymal stem cells to differentiate into adipocytes in culture has been shown repeatedly (Kim et al, 2010;Lim et al, 2011;Qian et al, 2010;Scott et al, 2011;Styner et al, 2010;Valorani et al, 2010;Welter et al, 2013) because sets of mesenchymal markers can be used to enrich adipogenic precursors from the stromal vascular fraction Rodeheffer et al, 2008). This was further corroborated by the identification of Pref-1 ( preadipocyte factor 1) as a marker for early adipocyte precursor cells (Hudak et al, 2014).…”