Decreased mitochondrial DNA copy number in children with cerebral palsy quantified by droplet digital PCR

Mitochondrial DNA copy number is a potential biomarker for mitochondrial dysfunction and is involved in a variety of disease states including autism, neurodegenerative diseases and traumatic brain injury, but few studies on mitochondrial DNA copy number in cerebral palsy have been reported. Therefore, this study aims to investigate the role of mitochondrial DNA copy number in children with cerebral palsy. A total of 104 children with cerebral palsy and 78 typically developing children were enrolled in this study. All children with cerebral palsy were diagnosed according to clinical criteria and furtherly divided into clinical subtypes. Mitochondrial DNA copy number was quantified by droplet digital PCR. We observed a significant reduction in mitochondrial DNA copy number from children with cerebral palsy comparing to healthy controls (216.76 ± 71.39 vs 359.66 ± 72.78, p < 0.001). An upward trend in mitochondrial DNA copy number alteration with the increase of age was found in healthy controls rather than in children with cerebral palsy. In addition, the mitochondrial DNA copy number in children with spastic hemiplegia was higher than that in children with spastic quadriplegia (152.27 ± 49.78 vs 90.64 ± 21.55, p = 0.001). Our results suggest that on the basis of accurate quantification by droplet digital PCR, the declined mitochondrial DNA copy number probably has certain implications for mitochondrial dysfunction in children with cerebral palsy, which provides a new clue for the investigation on the molecular mechanism and clinical characteristics of cerebral palsy.