Mitochondria transfer-based therapies reduce the morbidity and mortality of Leigh syndrome.

Mitochondria transfer is a recently described phenomenon in which donor cells deliver mitochondria to acceptor cells 1-3 . One possible consequence of mitochondria transfer is energetic support of neighbouring cells; for example, exogenous healthy mitochondria can rescue cell-intrinsic defects in mitochondrial metabolism in cultured ρ 0 cells or Ndufs4 - /- peritoneal macrophages 4-7 . Exposing haematopoietic stem cells to purified mitochondria before autologous haematopoietic stem cell transplantation allowed for treatment of anaemia in patients with large-scale mitochondrial DNA mutations 8,9 , and mitochondria transplantation was shown to minimize ischaemic damage to the heart 10-12 , brain 13-15 and limbs 16 . However, the therapeutic potential of using mitochondria transfer-based therapies to treat inherited mitochondrial diseases is unclear. Here we demonstrate improved morbidity and mortality of the Ndufs4 - /- mouse model of Leigh syndrome (LS) in multiple treatment paradigms associated with mitochondria transfer. Transplantation of bone marrow from wild-type mice, which is associated with release of haematopoietic cell-derived extracellular mitochondria into circulation and transfer of mitochondria to host cells in multiple organs, ameliorates LS in mice. Furthermore, administering isolated mitochondria from wild-type mice extends lifespan, improves neurological function and increases energy expenditure of Ndufs4 - /- mice, whereas mitochondria from Ndufs4 - /- mice did not improve neurological function. Finally, we demonstrate that cross-species administration of human mitochondria to Ndufs4 - /- mice also improves LS. These data suggest that mitochondria transfer-related approaches can be harnessed to treat mitochondrial diseases, such as LS.