Blood mir-331-3p is a potential diagnostic marker for giant panda (Ailuropoda melanoleuca) testicular tumor.

Background: In recent years, several giant pandas have suffered from testicular tumor, which has seriously affected giant panda health. However, the pathogenesis of testicular tumor in giant panda is still unclear. Studies have shown that miRNAs are involved in the occurrence and development of a variety of cancers. However, the effect of miRNAs on giant panda testicular tumor has been little studied. Therefore, this study explored the pathogenesis of giant panda testicular tumor through miRNA and mRNA sequencing, and screened out diagnostic markers of testicular tumor.

Results: Combined with phenotypic symptoms and pathological section results, three giant pandas were diagnosed with testicular tumor and divided into tumor group, and three other giant pandas were divided into normal group. A total of 29 differentially expressed miRNAs (DEmiRNAs) were screened by blood miRNA-seq, and 3149 target gene candidates were predicted. Functional enrichment analysis showed that the target genes were mainly involved in intermembrane lipid transfer and ATP-dependent chromatin remodeling. However, only 5 DEmiRNAs were screened by miRNA-seq of blood-derived exosomes and 364 target genes were predicted, which were mainly involved in antigen processing and presentation. In addition, 216 differentially expressed genes (DEGs) were screened by RNA-seq, and functional enrichment analysis showed that tumor-specific DEGs significantly enriched to protein phosphorylation. Spearman correlation analysis of miRNA-mRNA showed that the expressions of miR-331-3p and PKIG were significantly positively correlated (spearman = 0.943, p < 0.01), while the expressions of miR-331-3p and ENSAMEG00000013628 were significantly negatively correlated (spearman= -0.829, p < 0.05). RT-PCR showed that the expression of miR-331-3p was significantly decreased in giant panda with tumor (p < 0.01).

Conclusions: blood miRNAs and exosomal miRNAs exhibit distinct regulatory patterns concerning giant panda testicular tumor, potentially reflecting divergent biological processes in the disease's etiology. Meanwhile, miR-331-3p could be used as a potential diagnostic marker for giant panda testicular tumor. Our findings are conducive to the rapid clinical diagnosis of testicular tumor in giant pandas, and are also expected to provide scientific reference for further research on the pathogenesis of testicular tumor.