Transfer of mitochondria from astrocytes to neurons after stroke

In a mouse model of ischaemia, mitochondrial particles released from astroctyes are taken up by adjacent neurons, leading to enhanced cell survival signalling; disruption of this release mechanism resulted in worsened neurological outcomes. Emerging results suggest that neurons can transfer damaged mitochondria into adjacent astrocytes for disposal and recycling. Here Eng Lo and colleagues identify a transfer of healthy mitochondria in the opposite direction. In a mouse model of ischaemia, the authors demonstrate the release of mitochondrial particles from astrocytes that are taken up by adjacent neurons, leading to enhanced cell survival signalling. Disrupting this transfer led to worsened neurological outcomes. These findings suggest a previously unknown form of crosstalk between glia and damaged neurons, and suggest pathways that may be potentially targeted for improving stroke recovery in the future. Neurons can release damaged mitochondria and transfer them to astrocytes for disposal and recycling1. This ability to exchange mitochondria may represent a potential mode of cell-to-cell signalling in the central nervous system. Here we show that astrocytes in mice can also release functional mitochondria that enter neurons. Astrocytic release of extracellular mitochondrial particles was mediated by a calcium-dependent mechanism involving CD38 and cyclic ADP ribose signalling. Transient focal cerebral ischaemia in mice induced entry of astrocytic mitochondria into adjacent neurons, and this entry amplified cell survival signals. Suppression of CD38 signalling by short interfering RNA reduced extracellular mitochondria transfer and worsened neurological outcomes. These findings suggest a new mitochondrial mechanism of neuroglial crosstalk that may contribute to endogenous neuroprotective and neurorecovery mechanisms after stroke.