Comparative transcriptome analysis provides insight into the molecular targets and signaling pathways of deer TGF-1 regulating chondrocytes proliferation and differentiation.

Background: Chondrocytes are the only cell components in the cartilage, which has the poor regeneration ability. Thus, repairing damaged cartilage remains a huge challenge. Sika deer antlers are mainly composed of cartilaginous tissues that have an astonishing capacity for repair and renewal. Our previous study has demonstrated the transforming growth factor β (TGF-β1) is considered to be a key molecule involved in rapid growth, with the strongest expression in the cartilage layer. However, it remains to be clarified whether deer TGF-β1 has significantly different function from other species such as mouse, and what is the molecular mechanism of regulating cartilage growth.

Methods: Primary chondrocytes was collected from new born mouse rib cartilage. The effect of TGF-β1 on primary chondrocytes viability was elucidated by RNA sequencing (RNA-seq) technology combined with validation methods such as quantitative real-time polymerase chain reaction (qRT-PCR) and immunofluorescence assay (IFA). Differential expression genes were identified using the DEGseq package.

Results: Our results demonstrated that the overexpression of deer TGF-β1 possibly promoted chondrocyte proliferation and extracellular matrix (ECM) synthesis, while simultaneously suppressing chondrocyte differentiation through regulating transcription factors, growth factors, ECM related genes, proliferation and differentiation marker genes, such as Comp, Fgfr3, Atf4, Stat1 etc., and signaling pathways such as the MAPK signaling pathway, inflammatory mediator regulation of TRP channels etc. In addition, by comparing the amino acid sequence and structures between the deer TGF-β1 and mouse TGF-β1, we found that deer TGF-β1 and mouse TGF-β1 proteins are mainly structurally different in arm domains, which is the main functional domain. Phenotypic identification results showed that deer TGF-β1 may has stronger function than mouse TGF-β1.

Conclusion: ​These results suggested that deer TGF-β1 has the ability to promote chondrogenesis by regulating chondrocyte proliferation, differentiation and ECM synthesis. This study provides insights into the molecular mechanisms underlying the effects of deer TGF-β1 on chondrocyte viability.