Astrocytic monoamine oxidase B (MAOB)–gamma-aminobutyric acid (GABA) axis as a molecular brake on repair following spinal cord injury

Abstract

Neuroregeneration and remyelination rarely occur in the adult mammalian brain and spinal cord following central nervous system (CNS) injury. The glial scar has been proposed as a major contributor to this failure in the regenerative process. However, its underlying molecular and cellular mechanisms remain unclear. Here, we report that monoamine oxidase B (MAOB)-dependent excessive γ-aminobutyric acid (GABA) release from reactive astrocytes suppresses the CNS repair system by reducing brain‒derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) expression in severe spinal cord injury (SCI) animal models. Genetic deletion of MAOB in a mouse SCI model promotes both functional and tissue recovery. Notably, the selective MAOB inhibitor, KDS2010, facilitates recovery and regeneration by disinhibiting the BDNF-TrkB axis in a rat SCI model. Its dose-dependent effects were further validated in a monkey SCI model. Moreover, KDS2010 demonstrated a tolerable safety profile and dose-proportional pharmacokinetics in healthy humans during a phase 1 clinical trial. This pathway therefore represents a pivotal target for overcoming the intrinsic barriers to CNS repair after injury. Our findings identify the astrocytic MAOB‒GABA axis as a crucial molecular and cellular brake on the CNS repair system following SCI and highlight the translational potential of KDS2010 as a promising therapeutic candidate for SCI treatment.