Standardizing the lateral fluid percussion model of trauma in marmosets (Callithrix jacchus): regional vulnerability and inflammatory response.

Traumatic brain injury (TBI) is a major global health concern. The lateral fluid percussion injury (LFPI) model, widely used in rodents to simulate nonpenetrating TBI, has limited translational applicability due to anatomical differences between rodent and human brains. The common marmoset (Callithrix jacchus), a New World primate with a quasi-gyrencephalic brain, offers a promising alternative. This study aimed to standardize the LFPI model in marmosets by comparing trauma responses across parietal and temporal lobes. Ten adult marmosets underwent LFPI in these regions. Lesion volume was measured using Nissl staining; astrocytic and microglial responses were assessed via GFAP and Iba-1 immunofluorescence, and degenerating neurons were identified with Fluoro-Jade B. Righting reflex time and hemorrhage presence were evaluated as injury markers. Percussion aiming at the temporal lobe injury resulted in the most prominent lesions, epidural and subdural hematomas, and significant neuronal degeneration. Astrocytes showed longer processes after temporal trauma in the cortex and fewer branches in the hippocampal region CA1 than in the naive group. In contrast, hippocampal microglia showed fewer elongated branches in CA1 and dentate gyrus (DG), indicative of a reactive phenotype. Our results highlighted region-specific vulnerability, with temporal injury triggering the most pronounced inflammatory and degenerative responses. The marmoset LFPI model effectively mirrored key aspects of human TBI, supporting its translational relevance.