Comparative proteomics of small extracellular vesicles reveals immune-related biomarkers in moderate equine asthma - 09/05/26

Horses with moderate asthma (MA) exhibit subtle clinical signs, and diagnostic confirmation relies on tracheal mucus and/or bronchoalveolar lavage fluid (BALF) cytology. Small extracellular vesicles (sEV), carrying bioactive molecules reflecting their cells of origin, have emerged as promising tools for biomarker discovery in respiratory diseases. The objective is to characterize the proteomic content of sEV from BALF of MA horses.

BALF was prospectively collected from both lungs of 32 actively trained Trotters. sEVs were isolated within 12 hours using a commercial kit, characterized (size, concentration, morphology, and proteins) according to international guidelines, and analyzed by high-resolution MALDI-TOF mass spectrometry. Bioinformatic analyses were first conducted across groups (MA vs. control [CTL]), regardless of the lung side, and then separately on left and right BALFs within and between groups. Statistical thresholds were set at fold change > 1.5 and P < 0.01.

Six horses were excluded due to other respiratory conditions; 13 MA and 13 CTL horses were finally included. Seventeen proteins (10 upregulated, 7 downregulated) were differentially expressed in BALF of MA vs. CTL horses. In the right BALF, 32 proteins were dysregulated, and 11 in the left BALF. None of these proteins were differentially expressed between lungs within each group. Notably, Pentraxin 3 (PTX3), LOC100064703, and S100-A9 were consistently upregulated in all MA vs CTL comparisons. These proteins are involved in phagocytosis regulation, neutrophil aggregation, and antimicrobial activity.

These preliminary findings support the involvement of sEV in MA pathophysiology, and their relevance as putative biomarkers for equine asthma.