Intravenous administration of ex vivo expanded human umbilical cord blood-derived CD34⁺ cells in a preterm hypoxic-ischemic encephalopathy mouse model

Neonatal hypoxic-ischemic encephalopathy (HIE) in preterm infants lacks effective treatment and remains a leading cause of long-term neurological impairment. Autologous umbilical cord blood (UCB)-derived CD34⁺ cell therapy shows therapeutic potential; however, limited UCB volume in preterm infants often yields insufficient cells for clinical use. Recent advances in ex vivo expansion using chemically defined, albumin- and cytokine-free systems enable efficient proliferation of CD34⁺ hematopoietic stem cells. We evaluated the safety and efficacy of intravenously administered, ex vivo expanded CD34⁺ cells derived from human UCB in a mouse model of preterm HIE. Human UCB-derived CD34⁺ cells were cultured for 10 days using a chemically defined, serum- and cytokine-free expansion protocol. Mice with unilateral hypoxic-ischemic injury on postnatal day 5 received expanded or unexpanded CD34⁺ cells (1 × 10⁵ cells per animal) 48 h after injury. Expanded CD34⁺ cells were well tolerated and improved sensorimotor asymmetry, as assessed by the cylinder test, and reduced astrocyte and microglial activation in the injured brain compared with untreated HIE mice. Therapeutic effects did not significantly differ between expanded and unexpanded CD34⁺ cells. Ex vivo expansion under chemically defined conditions may enable autologous CD34⁺ cell therapy for preterm infants with limited UCB volume and represents a promising approach for regenerative treatment of neonatal brain injury.