Construction of the miRNA-mRNA regulatory networks for both the cartilage formation and remodel zones in the antler tip in sika deer (Cervus nippon)

Context. Deer antlers offer a premium model for investigating the mechanisms underlying arguably the most rapid cartilage formation and remodelling system. Although the cartilage formation process in the antler has been relatively intensively studied, thus far, at a molecular level, the cartilage remodelling has essentially been untouched. Aims. To construct miRNA-mRNA regulatory networks for both the cartilage formation and remodel zones in the antler tip. Methods. The tissues from both the cartilage formation zone (FZ) and remodel zone (RZ) in rapid growing antlers of sika deer were sampled, profiles of both mRNA and miRNA from these samples were sequenced and analysed, miRNA-mRNA regulatory networks for these two zones were constructed, and their encoded/targeted differentially expressed genes (DEGs) were identified through bioinformatics analysis. Key results. In total, 3703 DEGs in the FZ over the RZ were identified, with 1615 being upregulated and 2088 downregulated. The upregulated DEGs in the FZ were found to be mainly enriched in cell proliferation and chondrogenesis/osteogenesis, whereas those in the RZ were enriched in the formation of chondroclasts and osteoclasts. In total, 308 unique mature miRNAs were detected including 110 significantly differentially expressed miRNAs. These miRNAs are predicted to target extracellular matrix proteins, growth factors and receptors, and transcriptional factors, all related to cartilage formation and remodelling. To verify the reliability of our datasets, we successfully tested the regulatory function of one of the top 10 hub miRNAs, miR-155, in vitro. Conclusions. The miRNA-mRNA regulatory networks for cartilage formation zone (FZ) in relation to cartilage remodel zone (RZ) were successfully constructed, and validated, which has laid the foundation for the identification of potent growth factors and novel regulation system in bone formation through endochondral ossification.