Gene-modified Exosomes Protect the Brain Against Prolonged Deep Hypothermic Circulatory Arrest.

Background: Neurologic deficit remains a major complication after cardiovascular surgeries with deep hypothermic circulatory arrest (DHCA). We hypothesized that exosomes derived from bone marrow mesenchymal stem cells (MSCs) may conduct cerebral protection against prolonged DHCA in rats, and overexpressing microRNA-214 (miR-214) may further enhance the neuroprotection.

Methods: Cultured MSCs were transfected with lentivirus vectors containing pre-miR-214 or control vectors. Exosomes were isolated by centrifugation. The DHCA was conducted for 60 minutes when the pericranial temperature was cooled to 18°C. Exosomes from MSCs, MSCs transfected with control vectors, or pre-miR-214 were administered by intracerebroventricular injection 1 day before DHCA.

Results: Transfection of pre-miR-214 significantly enhanced the miR-214 expression in exosomes from MSCs. All exosome-pretreating groups exhibited lower levels of interleukin-1β and tumor necrosis factor-α, higher capillary density, more significant neurogenesis and angiogenesis, and more normal neurons in the hippocampus than those of the control group. Exosome pretreatment markedly improved the spatial learning and memory function and vestibulomotor function. Compared with exosomes from MSCs or MSCs transfected with control vectors, miR-214-enriched exosomes remarkably enhanced the miR-214 level and expressions of phosphor-protein kinase B and Bcl-2, inhibited expressions of phosphate and tension homology, Bcl-2 interacting mediator of cell death, Bcl-2-associated X protein, and cleaved Caspase-3, and increased the number of survival neurons. Significantly better neurologic functions were also detected in rats pretreated with miR-214-enriched exosomes.

Conclusions: Exosomes from MSCs conduct powerful neuroprotection against cerebral injury induced by DHCA, which can be further enhanced by genetic modification of the exosomes to overexpress miR-214.