Arginine Promotes Antler Reserve Mesenchymal Cell Proliferation and Chondrogenesis via Altered Wnt/β-catenin and mTOR Signaling.

Arginine (Arg) is a functional amino acid implicated in tissue growth, but its effects on deer antler reserve mesenchymal cells (RMCs) remain unclear. We evaluated Arg-induced changes in the proliferation and chondrogenic differentiation of RMCs in vivo and in vitro and characterized the associated transcriptomic signatures. Dietary supplementation with Arg increased the proportion of Ki67-positive cells in the mesenchymal cell-rich region of growing antlers. In vitro, Arg enhanced RMC viability and 5-Ethynyl-2'-deoxyuridine incorporation assay (EdU)incorporation in a dose-dependent manner, with 400 μM showing the strongest effect. RNA sequencing revealed broad transcriptional remodeling, with enrichment of extracellular matrix (ECM)/adhesion programs and growth-related pathways including PI3K-Akt, Wnt and mTOR signaling pathway. Arg also enhanced chondrogenic differentiation, as indicated by stronger Alcian blue staining and increased expression of SOX9 and COL2A1. During chondrogenic induction, Arg (800 μM) was associated with activation of mTOR signaling and attenuation of Wnt/β-catenin output. Collectively, these findings show that Arg promotes the expansion and chondrogenic differentiation of RMCs. Moreover, the Wnt/β-catenin and mTOR pathways are candidate signaling axes linked to Arg responses.