Transcriptomic signatures reveal systemic adaptations and immune modulation in response to training and competitive racing in horses.
Authors: Dąbrowska Izabela, Grzędzicka-Agko Jowita, Kiełbik Paula, Trela Michał, Witkowska-Piłaszewicz Olga
Journal: Equine veterinary journal
Summary
# Editorial Summary Researchers used RNA sequencing of peripheral blood samples to track how racehorses' molecular physiology changes across three distinct training and competitive phases—early training, mid-season training, and racing—collecting samples before and after exercise in 40 horses (29 Arabian and 11 Thoroughbreds). The transcriptomic profile revealed a clear progression: early training triggered acute stress responses with marked upregulation of immediate-early genes (FOS, FOSB) and heat shock proteins, whilst mid-season training showed a shift towards adaptive and recovery-oriented gene expression, with immune-related transcripts persisting but accompanied by remodelling genes (DNAJA1, HSPH1, CXCR4). Post-race samples demonstrated heightened stress activation through chemokine induction (particularly CCL5) and simultaneous suppression of certain immune regulators (IL18), suggesting a pattern of systemic stress combined with transient immunosuppression. For practitioners, these molecular signatures offer potential biomarkers to distinguish healthy training adaptation from maladaptive responses or overload—information that blood sampling could theoretically provide without invasive tissue sampling, though the study's limitation to three timepoints and peripheral blood assessment means caution is warranted before applying findings to individual clinical decisions. The transcriptomic approach holds promise for objectively monitoring training responses in equine athletes, particularly when integrated with conventional fitness assessments and clinical observation.
Read the full abstract on PubMed
Practical Takeaways
- •Blood transcriptomics can identify whether a horse is adapting appropriately to training or showing signs of overload—offering objective molecular markers beyond traditional fitness assessments
- •Different training phases produce distinct immune and stress signatures; monitoring these patterns could help optimize training intensity and detect problematic stress responses before clinical symptoms appear
- •Post-race immune suppression suggests a recovery window where horses may be more vulnerable to infection; consider management strategies that support immune recovery immediately after racing
Key Findings
- •Initial training (T1) triggered acute stress response with strong upregulation of immediate-early genes (FOS, FOSB, HSPA6) and immune activation
- •Mid-season training (T2) showed shift from acute stress to adaptive phase with prominent remodeling genes (DNAJA1, HSPH1, CXCR4) and persistent immune enrichment (KLRD1, CCL4, PRF1)
- •Post-race samples demonstrated heightened chemokine induction (CCL5), stress marker elevation (HSP90, JUN), and transient immune suppression (IL18, ARHGAP44 downregulation)
- •Peripheral blood transcriptomic signatures provide molecular biomarkers to distinguish physiological adaptation from overload in racehorses across training phases