Hypoxic Preconditioning Enhances the Potential of Mesenchymal Stem Cells to Treat Neonatal Hypoxic-Ischemic Brain Injury

BACKGROUND: Neonatal hypoxic-ischemic (HI) brain injury is one of the leading causes of long-term neurological morbidity in newborns. Current treatment options for HI brain injury are limited, but mesenchymal stem cell (MSC) therapy is a promising strategy to boost neuroregeneration after injury. Optimization strategies to further enhance the potential of MSCs are under development. The current study aimed to test the potency of hypoxic preconditioning of MSCs to enhance the therapeutic efficacy in a mouse model of neonatal HI injury. METHODS: HI was induced on postnatal day 9 in C57Bl/6 mouse pups. MSCs were cultured under hypoxic (hypoxic-preconditioned MSCs [HP-MSCs], 1% O 2 ) or normoxic-control (normoxic-preconditioned MSCs, 21% O 2 ) conditions for 24 hours before use. At 10 days after HI, HP-MSCs, normoxic-preconditioned MSCs, or vehicle were intranasally administered. Gold nanoparticle–labeled MSCs were used to assess MSC migration 24 hours after intranasal administration. At 28 days post-HI, lesion size, sensorimotor outcome, and neuroinflammation were assessed by hematoxylin and eosin staining, cylinder rearing task, and IBA1 staining, respectively. In vitro, the effect of HP-MSCs was studied on transwell migration, neural stem cell differentiation and microglia activation, and the MSC intracellular proteomic content was profiled using quantitative LC-MS/ms. RESULTS: Intranasally administered HP-MSCs were superior to normoxic-preconditioned MSCs in reducing lesion size and sensorimotor impairments post-HI. Moreover, hypoxic preconditioning enhanced MSC migration in an in vitro set-up, and in vivo to the lesioned hemisphere after intranasal application. In addition, HP-MSCs enhanced neural stem cell differentiation into more complex neurons in vitro but had similar anti-inflammatory effects compared with normoxic-preconditioned MSCs. Lastly, hypoxic preconditioning led to elevated abundances of proteins in MSCs related to extracellular matrix remodeling. CONCLUSIONS: This study shows for the first time that hypoxic preconditioning enhanced the therapeutic efficacy of MSC therapy in a mouse model of neonatal HI brain injury by increasing the migratory and neuroregenerative capacity of MSCs.