Table 1.

Effects of O₂ tension (between 2–18% O₂) on cellular metabolism, mitochondrial abundance, morphology, and network dynamics.

Cell Types	Experimental Conditions	Methods	Outcomes	Reference
Metabolic Effects
Stem cells	hMSCs/18% or 3% O2	Seahorse XF analysis, microarray, RT-PCR	↑ OCR/ECAR ratio at 18% O2 ↑ expression HIF targets involved in glucose metabolism at 3% O2	[19]
	hPSCs/18% or 5% O2	Seahorse XF analysis, NMR spectroscopy, RNA-seq, RT-PCR	↑ OCR/ECAR ratio at 18% O2 ↑ glycolytic intermediates at 3% O2 ↑ expression HIF targets involved in glucose metabolism at 3% O2	[60]
	MPCs from old mice/18% or 3% O2	Seahorse XF analysis	↓ OCR at 18% O2 ↑ ECAR at 18% O2	[25]
Primary differentiated cells	hCEnCs/18% or 2.5% O2	Seahorse XF analysis	↑ ECAR at 2.5% O2	[94]
	Rat primary cortical neurons/18% or 5% O2	ATP bioluminescent assay, LSC, lactate assay	↑ glucose uptake at 5% O2 ↓ glucose oxidation at 5% O2 ↑ lactate levels at 5% O2	[21]
	HRPTEC/18–3% O2	Resazurin assay	↑ metabolic activity at 18% O2, compared to 15% and 12% O2	[24]
Cancer/immortalized cells	U87MG/18–3% O2	Resazurin assay	↓ metabolic activity at 18% O2, compared to 8–3% O2
	MCF-7/18–3% O2	Resazurin assay	↓ metabolic activity at 18% O2, compared to 8% O2
	MCF-7/18% or 5% O2	Seahorse XF analysis	↓ basal and maximal OCR at 18% O2	[97]
	LNCaP/18% or 5% O2	Seahorse XF analysis	↓ basal OCR at 18% O2 ↑ maximal OCR at 18% O2
	Huh-7/18% or 5% O2	Seahorse XF analysis	↓ basal and maximal OCR at 18% O2
	SaOS2/18% or 5% O2	Seahorse XF analysis	↓ maximal OCR at 18% O2
Effects on mitochondrial morphology, abundance, and dynamics
Primary differentiated cells	rat primary neurons/18%, 5%, or 2% O2	TEM and confocal microscopy; Image J	Globular-shaped mitochondria at 18% O2 (versus elongated at 2% and 5% O2) ↓ mitochondrial network size, mitochondrial fraction, and mitochondrial perimeter at 18% O2	[99]
Cancer/immortalized cells	U87MG/18–3% O2	Confocal microscopy; Volocity	Rounder mitochondria at 18% O2	[24]
	HEK293/18–3% O2	Confocal microscopy; Volocity	Rounder mitochondria at 18% O2
	MCF-7/18–3% O2	Confocal microscopy; Volocity	Elongated mitochondria at 18% O2
	LNCaP/18% or 5% O2	Confocal microscopy; MiNA	↓ mitochondrial footprint at 18% O2 ↓ mean network size 18% O2	[97]
	Huh-7/18% or 5% O2	Confocal microscopy; MiNA	↑ mitochondrial footprint at 18% O2
	SaOS2/18% or 5% O2	Confocal microscopy; MiNA	↑ mitochondrial footprint at 18% O2 ↓ mean network size 18% O2

Abbreviations: ECAR, extracellular acidification rate; hCEnCs, human corneal endothelial cells; hMSCs, human mesenchymal stem cells; hPSC, human pluripotent stem cells; HRPTEC, human renal proximal tubule epithelial cells; LSC, liquid scintillation counting; MiNA, mitochondrial network analysis; NMR, nuclear magnetic resonance; OCR, oxygen consumption rate; TEM, transmission electron microscopy; XF, extracellular flux.