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Authors & Affiliations
Chiara Nappi, Espe Selva, Francisco J. Taberner
Abstract
Burns of diverse etiologies pose a significant health burden, resulting in varying levels of tissue damage and pain. Despite extensive research utilizing mouse models to elucidate burn-induced pain and recovery, discrepancies across different methodologies underscore the intricate complexity of burn pain and the necessity of standardized burn injury paradigms. To address this limitation, we developed the Burn Injury by Repeated Heat Exposure (BIRHE) model. By laying the hind paw for 10-seconds to a 52°C plate for 10 or 20 repetitions we reproducibly induce distinct pain intensities. We used the model to study the contribution of different nociceptors to burn pain.Our findings indicate that increasing BIRHE intensity leads to a marked reduction in acute mechanical and thermal pain thresholds accompanied by an increase in spinal interneuron recruitment. Notably, while thermal hyperalgesia was significantly reduced following TRPV1 fiber ablation, mechanical hyperalgesia was partially alleviated after MRGPRD fiber removal suggesting the contribution of other sensory fibers. Importantly, we observed disparities in paw inflammation and recovery of normal pain thresholds between female and male mice. Immunohistochemical studies on injured skin at different time points revealed sex-specific differences in the extent of damage to nociceptive terminals and regeneration rates, as well as the number and morphology of skin dendritic cells, which can account for the observed variations in pain behavioral outcomes.In summary, the BIRHE model recapitulates the common manifestations of pain following burn injury and offers a readily accessible and robust paradigm to investigate the peripheral and central mechanisms underlying pain sensitization.