title: Hypoxia Induces a Metabolic Shift and Enhances the Stemness and Expansion of Cochlear Spiral Ganglion Stem/Progenitor Cells.
abstract: Previously, we demonstrated that hypoxia (1% O2) enhances stemness markers and expands the cell numbers of cochlear stem/progenitor cells (SPCs). In this study, we further investigated the long-term effect of hypoxia on stemness and the bioenergetic status of cochlear spiral ganglion SPCs cultured at low oxygen tensions. Spiral ganglion SPCs were obtained from postnatal day 1 CBA/CaJ mouse pups. The measurement of oxygen consumption rate, extracellular acidification rate (ECAR), and intracellular adenosine triphosphate levels corresponding to 20% and 5% oxygen concentrations was determined using a Seahorse XF extracellular flux analyzer. After low oxygen tension cultivation for 21 days, the mean size of the hypoxia-expanded neurospheres was significantly increased at 5% O2; this correlated with high-level expression of hypoxia-inducible factor-1 alpha (Hif-1α), proliferating cell nuclear antigen (PCNA), cyclin D1, Abcg2, nestin, and Nanog proteins but downregulated expression of p27 compared to that in a normoxic condition. Low oxygen tension cultivation tended to increase the side population fraction, with a significant difference found at 5% O2 compared to that at 20% O2. In addition, hypoxia induced a metabolic energy shift of SPCs toward higher basal ECARs and higher maximum mitochondrial respiratory capacity but lower proton leak than under normoxia, where the SPC metabolism was switched toward glycolysis in long-term hypoxic cultivation.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Cheng-Kung Road, Taipei 114, Taiwan.
authors.forename: Hsin-Chien
authors.initials: HC
authors.lastname: Chen
authors.affiliation: Department of Otolaryngology, Auditory Medical Center, Cheng Hsin General Hospital, No. 45, Cheng Hsin Street, Taipei 112, Taiwan.
authors.forename: Jen-Tin
authors.initials: JT
authors.lastname: Lee
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Cheng-Kung Road, Taipei 114, Taiwan ; Graduate Institute of Medical Sciences, National Defense Medical Center, No. 161, Section 6, Minquan East Road, Taipei 114, Taiwan.
authors.forename: Cheng-Ping
authors.initials: CP
authors.lastname: Shih
authors.affiliation: Medical Research Center, Cardinal Tien Hospital, No. 362, Zhongzheng Road, Xindian District, New Taipei City 23148, Taiwan.
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Chao
authors.affiliation: Graduate Institute of Medical Sciences, National Defense Medical Center, No. 161, Section 6, Minquan East Road, Taipei 114, Taiwan ; Graduate Institute of Microbiology and Immunology, National Defense Medical Center, No. 161, Section 6, Minquan East Road, Taipei 114, Taiwan.
authors.forename: Huey-Kang
authors.initials: HK
authors.lastname: Sytwu
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Cheng-Kung Road, Taipei 114, Taiwan.
authors.forename: Shiue-Li
authors.initials: SL
authors.lastname: Li
authors.affiliation: Laboratory Animal Center, National Defense Medical Center, No. 161, Section 6, Minquan East Road, Taipei 114, Taiwan.
authors.forename: Mei-Cho
authors.initials: MC
authors.lastname: Fang
authors.affiliation: Graduate Institute of Medical Sciences, National Defense Medical Center, No. 161, Section 6, Minquan East Road, Taipei 114, Taiwan.
authors.forename: Hang-Kang
authors.initials: HK
authors.lastname: Chen
authors.affiliation: Graduate Institute of Medical Sciences, National Defense Medical Center, No. 161, Section 6, Minquan East Road, Taipei 114, Taiwan.
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Lin
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Cheng-Kung Road, Taipei 114, Taiwan.
authors.forename: Chao-Yin
authors.initials: CY
authors.lastname: Kuo
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Cheng-Kung Road, Taipei 114, Taiwan ; Graduate Institute of Medical Sciences, National Defense Medical Center, No. 161, Section 6, Minquan East Road, Taipei 114, Taiwan ; Graduate Institute of Microbiology and Immunology, National Defense Medical Center, No. 161, Section 6, Minquan East Road, Taipei 114, Taiwan.
authors.forename: Chih-Hung
authors.initials: CH
authors.lastname: Wang
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D015687:Cell Hypoxia / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D019069:Cell Respiration / Q000187:drug effects; D002469:Cell Separation; D002478:Cells, Cultured; D006019:Glycolysis / Q000187:drug effects; D007150:Immunohistochemistry; D008808:Mice, Inbred CBA; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology; D058985:Side-Population Cells / Q000166:cytology; D018874:Spheroids, Cellular / Q000166:cytology / Q000187:drug effects; D013136:Spiral Ganglion / Q000166:cytology*; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D015415:Biomarkers; D001973:Bromodeoxyuridine; D010100:Oxygen