Hypoxia-mediated carbohydrate metabolism and transport promotes early stage murine follicle growth and survival.
Am J Physiol Endocrinol Metab. 2014 Feb 25;
Authors: Makanji Y, Tagler D, Pahnke J, Shea LD, Woodruff TK
Oxygen tension is critical for follicle growth and metabolism, especially for early-stage follicles where vascularity is limited. Its role and underlying mechanism in the in vitro activation and maturation of immature to ovulatory follicles, is largely unknown. In this study, early secondary (100 μm) murine follicles were isolated and encapsulated in alginate hydrogels to replicate the in vivo environment of the growing/maturing follicle. Encapsulated follicles were cultured for 8 days at either 2.5% O2 or 20% O2. Survival (2.6-fold) and growth (1.2-fold) were significantly higher for follicles cultured at 2.5% O2 compared to 20% O2. Using a mouse hypoxia signaling pathway qRT-PCR array and GeneGo Metacore analysis, we found that direct target genes of hypoxia-activated HIF1-complex were significantly up-regulated in follicles cultured for 8 days at 2.5% O2 compared to 20% O2, including the carbohydrate transport and metabolism genes Slc2a3, Vegfa, Slc2a1, Edn1, Pgk1, Ldha, and Hmox1. Other up-regulated genes included carbohydrate transporters (Slc2a1, Slc2a3 and Slc16a3) and enzymes essential for glycolysis (Pgk1, Hmox1, Hk2, Gpi1, Pfkl, Pfkp, Aldoa, Gapdh, Pgam1, Eno1, Pkm2 and Ldha). For follicles cultured at 2.5% O2, a 7.2-fold up-regulation of Vegfa correlated to an 18-fold increase in VEGFA levels and a 3.2-fold up-regulation of Ldha correlated to a 4.8-fold increase in lactate levels. Both VEGFA and lactate levels were significantly higher in follicles cultured at 2.5% O2 compared to 20% O2. Therefore, enhanced hypoxia-mediated glycolysis is essential for growth and survival of early secondary follicles, and provides vital insights into improving in vitro culture conditions.
PMID: 24569591 [PubMed - as supplied by publisher]