Histological and Transcriptomic Characterization of Full-Thickness Skin Wound Healing in Maraena Whitefish (Coregonus maraena Bloch, 1779)

The healing process of full-thickness skin wounds in maraena whitefish (<i>Coregonus maraena</i>) was investigated to provide preliminary insights into the species' tissue regeneration mechanism and dynamics following mechanical injury-simulating standard aquaculture PIT tagging procedures. A mechanical skin injury was induced on the dorsal flank of one-year-old maraena whitefish using a 15G needle, and skin regeneration was tracked for 15 days post-wounding (dpw). Expression levels of six genes involved in immune response and inflammation (<i>IL-17D</i> and <i>CD-4</i>), cellular stress response (<i>HSP-90</i>), and cell proliferation and tissue growth (<i>MMP-9</i>, <i>p53</i>, and <i>TGF-β</i>) were examined in wounded and intact skin tissues, liver, and head kidney. Histological analyses were also performed to monitor wound-healing progression. Histological examination revealed typical fish wound-healing characteristics involving re-epithelialization on the 1st day post-wounding (dpw), acute inflammation on the 3rd dpw, granulation tissue formation and intensive wound remodeling on the 8th dpw, and full tissue regeneration by the 15th dpw. Gene expression analysis revealed dynamic tissue-specific patterns: <i>IL-17D</i> and <i>CD-4</i> were upregulated early in wounded skin, indicating rapid immune and inflammation activation, while <i>MMP-9</i> and <i>TGF-β</i> peaked later, supporting tissue remodeling and regeneration. <i>HSP-90</i> and <i>p53</i> genes were highly expressed in the mid to late stage of healing, reflecting cellular stress response associated with acute inflammation and a high rate of cell proliferation in wounded skin. Significant transcriptional changes in the liver and head kidney further supported the systemic nature of the wound response and emphasized the importance of immune function in the species' tissue-repair process. The obtained findings provide novel insights into the mechanisms and dynamics of skin healing in maraena whitefish, potentially supporting the development of improved health management strategies for this species in aquaculture.