Neuronal Injury and Regeneration-Linked Gene Expression Dynamics in the Hypothalamic-Pituitary-Adrenal Axis Following Experimental Traumatic Brain Injury.

Traumatic brain injury (TBI) induces complex molecular and neuroendocrine alterations that extend beyond the site of injury. The hypothalamic-pituitary-adrenal (HPA) axis, a hierarchically organized neuroendocrine system composed of the hypothalamus, pituitary gland, and adrenal glands, plays a central role in coordinating stress and metabolic homeostasis. Despite its critical importance, the temporal transcriptional mechanisms underlying HPA axis dysregulation following TBI remain poorly understood, particularly in relation to coordinated neuronal injury and regeneration processes. This study aimed to investigate the time-dependent transcriptional dynamics of genes associated with neuronal injury and regeneration within the HPA axis following experimental TBI. Moderate-to-severe TBI was induced in Sprague-Dawley rats using a controlled cortical impact (CCI) model. Animals were allocated into sham, acute (24 h), and chronic (30 days) groups. Transcript profiles of 24 HPA axis- and neuroregeneration-related genes were analyzed in hypothalamic, pituitary, and adrenal tissues using quantitative real-time PCR, with normalization to a housekeeping gene and statistical evaluation of differential expression across time points. TBI induced distinct, tissue-specific, and time-dependent transcriptional alterations across the HPA axis. In the acute phase, stress-response genes showed divergent regulation between central and peripheral tissues, whereas the chronic phase was characterized by transcriptional reorganization involving neurotrophic, metabolic, and neuroendocrine pathways. Key regulators such as Hif1a, Rad18, Avp, Gata3, and OxtR exhibited significant and region-specific expression changes. These findings demonstrate that TBI triggers coordinated yet heterogeneous transcriptional responses within the HPA axis, linking central injury to systemic endocrine adaptation. This study provides novel insight into the molecular basis of neuroendocrine dysfunction and recovery after TBI and identifies candidate targets for future therapeutic strategies.