Characterization of Temperature-Dependent Cellular Responses in a Novel Larval-Derived Rainbow Trout Cell Line

Reliable fish cell models are essential for studying cellular processes under controlled in vitro conditions and thereby reducing the need for animal experiments. In this study, we established and characterized OMYlar5, a novel larval cell line derived from rainbow trout (Oncorhynchus mykiss). OMYlar5 demonstrated sustained proliferative capacity over at least 60 passages, indicating spontaneous immortalization and its suitability for long-term applications in fish biology and aquaculture research. To investigate temperature-dependent cellular responses, cells were cultured at 18, 20, and 22 °C, and changes in growth, morphology, cytoskeletal organization, stress responses, and gene expression were analyzed. Increased temperature enhanced cell proliferation, whereas the expression of the proliferation-associated genes pcna and c-myc remained unchanged. Temperature-dependent alterations in cell morphology and F-actin organization were observed, with enhanced actin bundle formation at 22 °C. However, no significant induction of Hsp70 or Hsp90 was detected at the transcript or protein level, suggesting that the tested temperature range was not associated with detectable induction of these heat shock proteins. Furthermore, OMYlar5 cells expressed nanog, nes, pax3, and sox9, whereas pou5f1 and sox2 were expressed at very low levels. These expression patterns provide information on the molecular characteristics of the cell line. Overall, OMYlar5 may provide a useful in vitro model for investigating temperature responses, cellular physiology, and developmental processes in rainbow trout.