Grass carp S100A10a/10b, two skin wound-induced genes, augment epithelial cell proliferation and migration in vitro

S100A10 protein, a member of S100 protein family, has been extensively studied in mammalian models. In fish species, evolution of S100 proteins including S100A10 has been clarified, revealing that two paralogous genes, S100A10a and S100A10b, arose in teleosts through the fish-specific whole-genome duplication event. However, the functional roles of fish S100A10 genes remain largely uncharacterized. In the present study, we identified two S100A10 homologs in grass carp, designated gcS100A10a and gcS100A10b, and demonstrated that their mRNA is highly expressed in grass carp skin and strongly upregulated after skin trauma by real-time quantitative PCR. Using the fish epithelial cell line, Epithelioma papulosum cyprini (EPC) cells, as a model, we showed that overexpression of gcS100A10a or gcS100A10b enhances cell viability, increases expression of proliferating cell nuclear antigen (PCNA), and promotes DNA synthesis, thereby demonstrating their capacity to stimulate cell proliferation. Flow cytometric analysis further uncovered that both proteins accelerate EPC cell cycle progression by promoting transition into the S and G2/M phases. Additionally, gcS100A10a and gcS100A10b significantly elevate EPC cell migration and this elevation is attenuated by a broad-spectrum matrix metalloproteinase (MMP) inhibitor, GM6001, suggesting involvement of MMP activity in this process. This suggestion is strongly supported by findings that overexpression of gcS100A10a or gcS100A10b increases extracellular MMP activity and decreases intracellular MMP accumulation although ‌MMP-2/MMP-9 mRNA levels remain unchanged. Collectively, these results demonstrate the positive regulation of gcS100A10a and gcS100A10b on fish epithelial cell proliferation and migration, together with their high and injury-inducible expression in grass carp skin, indicating their possible involvement in fish skin wound healing.