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Transcriptomic Analysis of Skeletal Muscle Regeneration Across Mouse Lifespan Identifies Altered Stem Cell States

Walter et al., Nature Aging. 2024.

https://pubmed.ncbi.nlm.nih.gov/39578558

Age-related skeletal muscle regeneration dysfunction is poorly understood. Using single-cell transcriptomics and high-resolution spatial transcriptomics, researchers evaluated factors contributing to age-related decline in skeletal muscle regeneration after injury in young, old, and geriatric male and female mice (5, 20, and 26 months old). Eight immune cell types were identified and associated with age-related dynamics and distinct muscle stem cell states specific to old and geriatric tissue. The findings emphasize the role of extrinsic and intrinsic factors, including cellular senescence, in disrupting muscle repair. This study provides a spatial and molecular framework for understanding regenerative decline and cellular heterogeneity in aging skeletal muscle. Supported by ORIP (F30OD032097), NIA, NIAID, NIAMS, NICHD, and NIDA.

Metabolic Transitions Define Spermatogonial Stem Cell Maturation

Voigt et al., Human Reproduction. 2022.

https://www.doi.org/10.1093/humrep/deac157

The spermatogonial stem cell (SSC) is the basis of male fertility. One potential option to preserve fertility in patients treated with anti-cancer therapy is isolation and laboratory culture of the juvenile SSC pool with subsequent transplantation to restore spermatogenesis. However, efficient culture of undifferentiated spermatogonia, including SSCs, in mammals other than rodents remains challenging. Investigators reported that the metabolic phenotype of prepubertal human spermatogonia is distinct from that of adult spermatogonia and that SSC development is characterized by specific metabolic transitions from oxidative phosphorylation to anaerobic metabolism. Supported by ORIP (R01OD016575) and NICHD.

HDAC Inhibitor Titration of Transcription and Axolotl Tail Regeneration

Voss et al., Frontiers in Cell and Development Biology. 2021.

https://pubmed.ncbi.nlm.nih.gov/35036404/

New patterns of gene expression are enacted and regulated during tissue regeneration. Romidepsin, an FDA-approved HDAC inhibitor, potently blocks axolotl embryo tail regeneration by altering initial transcriptional responses to injury. Regeneration inhibitory concentrations of romidepsin increased and decreased the expression of key genes. Single-nuclei RNA sequencing at 6 HPA illustrated that key genes were altered by romidepsin in the same direction across multiple cell types. These results implicate HDAC activity as a transcriptional mechanism that operates across cell types to regulate the alternative expression of genes that associate with regenerative success versus failure outcomes. Supported by ORIP (P40OD019794, R24OD010435, R24OD021479), NICHD, and NIGMS.

Fructose Stimulated De Novo Lipogenesis Is Promoted by Inflammation

Jelena  et al., Nature Metabolism. 2020.

https://pubmed.ncbi.nlm.nih.gov/32839596

Non-alcoholic fatty liver disease (NAFD) affects 30% of adult Americans. While NAFD starts as simple steatosis with little liver damage, its severe manifestation as non-alcoholic steatohepatitis (NASH) is a leading cause of liver failure, cirrhosis, and cancer. Fructose consumption is proposed to increase the risk of hepatosteatosis and NASH. Excessive intake of fructose causes barrier deterioration and low-grade endotoxemia. Using a mouse model, the study examined the mechanism of how fructose triggers these alterations and their roles in hepatosteatosis and NASH pathogenesis. The results demonstrated that microbiota-derived Toll-like receptor (TLR) agonists promote hepatosteatosis without affecting fructose-1-phosphate (F1P) and cytosolic acetyl-CoA. Activation of mucosal-regenerative gp130 signaling, administration of the YAP-induced matricellular protein CCN1 or expression of the antimicrobial peptide Reg3b (beta) counteract fructose-induced barrier deterioration, which depends on endoplasmic-reticulum stress and subsequent endotoxemia. Endotoxin engages TLR4 to trigger TNF production by liver macrophages, thereby inducing lipogenic enzymes that convert F1P and acetyl-CoA to fatty acid in both mouse and human hepatocytes. The finding may be of relevance to several common liver diseases and metabolic disorders. Supported by ORIP (S10OD020025), NCI, NIEHS, NIDDK, NIAID, and NIAAA.