Mitochondrial DNA copy number (mtDNA-CN) refers to the total number of mitochondrial DNA molecules within a cell, which varies depending on cell type and environmental factors. This variation provides critical insights into cellular health and function. A reduction in mtDNA-CN can signal changes in the cellular environment, potentially triggered by various factors, including stress or disease. The regulation of mtDNA-CN is governed by mitochondrial replication processes and influenced by factors such as energy demand, nutrient availability, and aging.

Several methods are used to measure mtDNA-CN, including quantitative PCR (qPCR), digital PCR (dPCR), and next-generation sequencing (NGS). These techniques enable accurate quantification, although each has limitations. MtDNA-CN is increasingly recognized as a potential biomarker for various health conditions, including cancer, neurodegenerative diseases, and aging-related disorders. Research indicates that mtDNA-CN could reflect mitochondrial biogenesis, oxidative stress, or cellular aging, making it a valuable tool in disease diagnosis and monitoring.

Despite its potential, challenges remain in standardizing mtDNA-CN measurements and understanding its role in different tissues and conditions. Further research is needed to fully realize its clinical utility and to explore its implications in health and disease.