Porcine Fetal-Derived Fibroblasts Alter Gene Expression and Mitochondria to Compensate for Hypoxic Stress During Culture

The Warburg effect is characterized by decreased mitochondrial oxidative phosphorylation and increased glycolytic flux in adequate oxygen. The preimplantation embryo has been described to have characteristics of the Warburg effect, including similar changes in gene expression and mitochondria, which are more rudimentary in appearance. We hypothesized hypoxia would facilitate anaerobic glycolysis in fibroblasts thereby promoting gene expression and media metabolite production reflecting the Warburg effect hallmarks in early embryos. Additionally, we speculated that hypoxia would induce a rudimentary small mitochondrial phenotype observed in several cell types evidenced to demonstrate the Warburg effect. While many have examined the role hypoxia plays in pathological conditions, few studies have investigated changes in primary cells which could be used in somatic cell nuclear transfer. We found that cells grown in 1.25% O(2) had normal cell viability and more, but smaller mitochondria. Several hypoxia-inducible genes were identified, including seven genes for glycolytic enzymes. In conditioned media from hypoxic cells, the quantities of gluconolactone, cytosine, and uric acid were decreased indicating higher consumption than control cells. These results indicate that fibroblasts alter gene expression and mitochondria to compensate for hypoxic stress and maintain viability. Furthermore, the metabolic changes observed, making them more similar to preimplantation embryos, could be facilitating nuclear reprogramming making these cells more amendable to future use in somatic cell nuclear transfer.