Circulating microRNAs (ECmiRNAs) are small regulatory RNAs that may function as biomarkers for heat stress (HS). This study analyzed the effects of HS on the ECmiRNA profile of 2 genotypes, Iberian purebred (IB) and Duroc × Iberian crossbred (DUIB) pigs. Forty pigs (20 per genotype) were housed individually and exposed to thermoneutral conditions (22°C) for one week, followed by another week of HS (30°C), across 2 consecutive batches. Plasma samples were collected at 3 time points: before HS (T0), 2 d after HS onset (T2), and 7 d after HS onset (T7). Sixty plasma samples (5 pigs per genotype and batch, per time point) were sequenced using the NEBNext® Small RNA Library Kit. After quality control and trimming, ECmiRNAs were identified with miRDeep2 (v. 0.1.3). Differential expression analyses were performed using edgeR, and functional implications were explored via DIANA-miRPath v4.0, using TarBase v8.0 and Gene Ontology (GO) as annotation sources. On average, 4.87 million out of 13.37 million reads per sample remained after trimming and quality control. Of these, 3.45 million (83.13%) mapped to the Sscrofa11.1 reference genome, with 67.97% identified as miRNAs, resulting in 156 detected ECmicroRNAs. No significant batch effects were observed on the ECmiRNA profile. However, HS response differed by genotype: in IB pigs, 5, 7, and 2 ECmiRNAs were differentially expressed (DE) in T0 vs. T2, T0 vs. T7, and T2 vs. T7, respectively. In DUIB pigs, no differences were detected in T0 vs. T2, but 3 and 7 ECmiRNAs were differentially expressed in T0 vs. T7 and T2 vs. T7, respectively. Four DE ECmiRNAs were identified as regulators of HS response (hsa-let-7d-5p, hsa-miR-432–5p, hsa-miR-450b-5p, hsa-miR-9–3p), while 3 were linked to stress granule assembly (hsa-miR-19b-3p, hsa-miR-30b-5p, hsa-let-7d-5p). These findings suggest genotype-dependent differences in response to HS. This work has received funding from the European Union’s Horizon Europe research and innovation program under the grant agreement No 01059609 (Re-Livestock project).
Aranguren-Rivas et al. (Wed,) studied this question.