Transcriptomic dynamics of the elite hibernator and cold-stressed human cells: potential insights into mammalian hibernation

Golden-mantled ground squirrels (Callospermophilus lateralis) are elite hibernators. Seasonal torpor secondary to environmental extremes elicits a reduction in body temperature (Tb) to approximately 4°C and oxygen consumption rates 1/100th of euthermic rates. Many hibernators are not capable of Tb reduction and metabolic depression to this degree; instead, mammalian hibernators employ varied strategies and undergo torpor at Tb’s ranging from cold (rodents) to hot (bears). We studied the ground squirrel model as a hibernator as they can execute torpor over a wide temperature range, evaluating nuances in physiological and molecular strategies across hot, warm, and cold torpor. We performed transcriptomic analysis of brain, heart, liver, and kidney tissues collected from ground squirrels during the early phase of torpor across a range of ambient temperatures (4, 12, 20, 25, 30°C). The highest number of differentially expressed genes (DEG’s) in the brain was between the euthermic squirrels and those torpid at 25ºC (3425 DE genes; pFDR<0.01). The highest number of DEG’s for heart (2742 genes), liver (3586 genes), and kidney tissue (2233 genes) occurred between euthermic squirrels and those torpid at 20ºC. These results suggest warm torpid temperatures around 20-25ºC induce the most robust molecular response, indicating there may be cellular dysregulation occurring. Using WGCNA, we produced a consensus network of genes demonstrating correlated differential expression in all four tissues and across all pairwise comparisons between the euthermic squirrels and each experimental torpor temperature, this network contained 488 genes. Pathway analysis within the consensus network highlights enrichment of key pathways related to ubiquitination, RNA binding, DNA repair, and alternative splicing. To elucidate human cells responses to metabolic depression, mirroring a torpor-like state, a 24-hour temperature exposure was performed at the torpor temperatures listed above. Human cells were chosen to reflect tissues investigated in the squirrel model including a human astrocytoma cell line, AC-16 cardiomyocytes, HEK-293T, and HEPG2 cells. Temperature-responsive differential gene expression was compared between cells kept in 37°C incubators and cold-stressed cells at each experimental temperature. The highest number of DEG’s for heart (7,979), brain (8,339), and kidney cells (8,610) were between cells kept at 37°C and those cold-stressed at 25°C. In the liver, the most DEG’s were found between cells at 20°C and 4°C (8,707), cells kept at 37°C and those stressed at 25°C had (6,421) DEG’s. Investigating the temperature-specific differences occurring in conjunction with consensus responses will tease apart molecular strategies mammals engage across wide ranging hibernation phenotypes. Funded by the Translational Research Institute for Space Health This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.