Intranasal Wharton's Jelly-Derived Mesenchymal Stem Cell Therapy, Alone or in Conjunction With Therapeutic Hypothermia, Alleviates Neonatal Hypoxic-Ischemic Brain Injury in Mice

Objective: Neonatal hypoxic-ischemic brain injury (HIBI) caused by perinatal asphyxia is a primary cause of long-term neurological morbidity. Hypothermia is the sole available clinical intervention despite its limited efficacy. Intranasal mesenchymal stem cells (MSCs) show promise for the treatment of HIBI. This study explores the efficacy, migration, treatment window, and therapeutic mechanisms of intranasally applied Wharton's jelly-derived MSCs (WJ-MSCs) in a neonatal HIBI mouse model, and assesses its therapeutic benefit in conjunction with hypothermia. Methods: Nine-day-old C57BL/6 mice underwent hypoxia-ischemia (HI), with or without hypothermia, and were intranasally dosed with 0.1 to 2.0 × 10 ⁶ WJ-MSCs, at 3 or 10 days post-HI. WJ-MSCs were traced using different techniques. Neurogenesis was examined 2 days post-treatment. Neuroinflammation, sensorimqotor outcome, and neuronal tissue loss was assessed 28 days post-HI. Additionally, anti-inflammatory and neuroregenerative properties of WJ-MSCs were investigated in non-contact co-cultures with microglia and neural stem cells, and by secretome profiling. Results: Intranasally delivered WJ-MSCs reduced HI-induced lesion size and sensorimotor impairments. WJ-MSCs expressed multiple receptors for upregulated chemokines in the HI-lesion, and migrated from the nasal cavity into the meninges and brain parenchyma. WJ-MSCs secreted a broad spectrum of immunomodulatory and neuroregenerative proteins, and inhibited neuroinflammation and boosted neuroregeneration in vivo and in vitro. WJ-MSC potency was sustained across different donors. Importantly, intranasal WJ-MSCs augmented the therapeutic benefits of hypothermia following neonatal HIBI in mice. Interpretation: This study provides new translational evidence that intranasal WJ-MSCs, either alone or in combination with hypothermia, mitigate the consequences of neonatal HIBI by resolving inflammation and boosting neurorepair through their secretome. ANN NEUROL 2025;98:1380–1394.