Post-hemorrhagic hydrocephalus (PHH) is a common neurological disorder affecting neonates and infants, characterized by increased head size, cerebrospinal fluid (CSF) accumulation, and CNS disability. Neurosurgical removal of CSF offers palliative treatment, yet affected individuals still suffer from neurological sequelae and a need for continual CSF removal and shunt revisions. No truly disease-modifying therapies are currently available. Our proposal explores a new mechanism in the etiology of PHH, particularly occurring during prenatal or premature life, through the actions of lysophospholipids (LPs). These small, membrane- derived lipids include the glycerophospholipid known as lysophosphatidic acid (LPA) that can be present at high levels in blood or hemorrhagic fluids. LPA activates a family of LPA receptors, and preliminary data demonstrate the involvement of at least one receptor, LPA1, in mediating the actions of hemorrhagic fluids and LPA in promoting PHH in an animal model. This model also recapitulates comorbid changes within the brain that have been associated with prenatal PHH in humans. Three specific aims will be pursued over a 5-year period to test the hypothesis that the initiation and progression of PHH involves LPA signaling that further provides a foundation for developing new, therapeutic approaches. Aim 1. Assess effects of prenatal LPA exposure on neuroanatomical changes associated with PHH. Aim 2. Assess intracranial fluid composition and compartments in the PHH mouse model. Aim 3. Determine LPA-dependent PHH developmental timing and assess therapeutic tractability.