A Modified Repetitive Closed Head Injury Model Inducing Persistent Neuroinflammation and Functional Deficits Without Extensive Cortical Tissue Destruction

Traumatic brain injury (TBI) remains a significant clinical challenge, with limited treatment options and long-term neurological impairments. Mild to moderate TBI represents the most common form, making it a critical therapeutic target. However, current animal models poorly reflect human TBI pathophysiology, necessitating improved preclinical paradigms. Here, we present a refined repetitive closed head injury (rCHI) model using consecutive controlled impacts within a single session, without craniotomy. We initially compared closed head injury (CCI) and rCHI models showing that the rCHI model enables precise impact application while preserving brain macrostructure. We evaluated the acute and chronic effects of increasing injury severity through 1, 3, or 5 consecutive impacts in adult C57BL6/J mice. MRI revealed severity-dependent blood-brain barrier (BBB) disruption, with significant gadolinium leakage in the 3- and 5-impact groups. Neuroinflammatory responses, assessed by immunofluorescence and qRT-PCR, demonstrated proliferation of microglia (IBA1) and astrocytes (GFAP), alongside increased inflammatory markers (<i>NOS2</i>, <i>NOX2</i>, <i>Casp1</i>, <i>IL-1</i>β, <i>TNF</i>-α). Functional assessments (beam walk, CatWalk gait analysis, novel object recognition) confirmed sustained motor and cognitive deficits in the 5-impact group over 28 days. Diffusion MRI indicated persistent white matter alterations supporting progressive neurodegeneration. This rCHI model successfully replicates key TBI features-BBB dysfunction, chronic neuroinflammation, and functional impairments-without direct cortical destruction. It serves as a valuable platform for evaluating acute-phase interventions and investigating neuroprotective strategies targeting inflammation and BBB integrity. Our findings highlight the importance of injury severity in shaping TBI outcomes and reinforce the need for tailored therapeutic approaches.