Dual transcriptomics of Besnoitia besnoiti infected fibroblasts reveals hallmarks and molecular biomarkers of early fibrosis associated to TGF beta upregulation and MAPK signalling and novel parasite effectors

Endothelial activation, inflammation and fibrosis are predominant lesions in the testis of sterile bulls that may end up with sterility during acute and chronic besnoitiosis. Moreover, fibroblasts, that are key players in fibrosis, are parasite target cells during Besnoitia besnoiti chronic infection. Thus, the purpose of the study was to dissect the underlaying molecular mechanisms that promote a drift towards fibrosis during the disease progression. A dual transcriptomic analysis was carried out at two times post-infection (p.i.), representative of invasion (12 h p.i.) and intracellular proliferation (32 h p.i.) in primary bovine aorta fibroblasts infected with B. besnoiti tachyzoites. Once relevant host pathways were identified, we investigated the expression of relevant differentially expressed genes (DEGs), in the scrotal skin of sterile naturally infected bulls.Functional enrichment analyses of DEG in the in vitro model revealed shared hallmarks of cancer and early fibrosis. Inflammation, angiogenesis and apoptosis stood out at 12 h p.i., and ECM remodelling, cell migration and proliferation at 32 h p.i. Interestingly, some DEGs were also regulated in the scrotal skin of naturally infected bulls (PLAUR, TGF beta-1 and FosB). We have identified potential biomarkers of the different phases of fibrosis that may hold prognostic significance. Ultimately, we identified potential parasite effectors primarily associated with host cell invasion, protein synthesis and metabolism that might promote parasite survival leading to chronic infection. Finally, both host and parasite pathways emerge as potential therapeutic targets.