Variant load of Mitochondrial DNA in single human Mesenchymal stem cells

Abstract

Abstract Mesenchymal stem cells (MSCs) are the parent cells to many cells of the musculoskeletal system including osteoblasts. Previous work has shown that in mouse models mitochondrial DNA (mtDNA) pathological variants lead to dysfunction of the respiratory chain of these osteoblasts and the premature development of age related osteoporosis. An increased rate of respiratory chain deficiency has also been observed in human osteoblasts. An experimental pipeline to isolate single MSCs using flow cytometry was developed before performing next generation sequencing to analyse the pathogenic variant load of 13 patients aged 22-88. In all patients, somatic mtDNA variants were detected in individual cells. As per previous studies, increased variants within the mtDNA control region (D-Loop) were detected. However overall, there was no significant difference in the distribution of variants across the rest of the genome in all patients. Although a higher proportion of non-synonymous variants were seen this was not statistically significant. It is possible to isolate and sequence individual MSCs and detect somatic mtDNA variants. This gives a snapshot in time of the variant load for each patient. Due to low sample numbers when compared to studies investigating the role of pathogenic mtDNA variants in other cell types, it was not possible to observe any age related increase in pathological variants. However, this this study adds further evidence that clonally expanded, somatic mtDNA variants are common and could contribute to age related diseases including osteoporosis.