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

In the present study the healing process of full-thickness skin wounds in maraena whitefish (Coregonus maraena) was investigated through histological and gene expression analyses. A mechanical skin injury was induced on the dorsal flank of one-year-old maraena whitefish using a 15G needle to mimic aquaculture tagging procedures and skin regeneration was tracked for 15 days post wounding (dpw). Expression of six genes involved in immune response and inflammation (IL-17D, CD-4), cellular stress response (HSP-90) and cell proliferation and tissue growth (MMP-9, p53, TGF-β) was examined in wounded and intact skin tissues, as well as in the liver and head kidney. Histological examination in the studied species revealed a typical for fishes wound healing progression characteristics with re-epithelization (at 1st dpw), acute inflammation (at 3rd dpw), granulation tissue formation and intensive wound remodeling (at 7th dpw), as well as full tissue regeneration with restored skin architecture at 15 dpw. Gene expression profiling of all analyzes genes revealed dynamic, tissue-specific patterns, indicating an orchestrated systemic response to injury. In wounded skin, IL-17D and CD-4 showed early upregulation, indicating rapid immune and inflammation activation, while MMP-9 and TGF-β peaked at later stages, reflecting their roles in tissue remodeling and regeneration. HSP-90 and p53 were also elevated expressed in the wounded skin, particularly during the mid to late healing phases, indicating elevated cellular stress response associated with acute inflammation and a high rate of cell proliferation. Pronounced changes in mRNA transcription levels of the examined genes were also detected in the liver and head kidney, indicating a systemic nature of the skin wound response and highlighting the critical role of immunity in injury regeneration in this species. The obtained in the present study findings provide novel insights into the principles and dynamics of skin repair mechanisms in maraena whitefish, supporting the future development of improved fish health management strategies in aquaculture.