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 ρ⁰ 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 limbs¹⁶. 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.