miR-370-3p Inhibited the Proliferation of Sheep Dermal Papilla Cells by Inhibiting the Expression of SMAD4

The proliferation and maturation of hair follicles in follicular papilla cells are predominantly governed by miRNAs, which significantly influence the cell cycle, apoptosis, and proliferation. <i>miR-370-3p</i> has been associated with several biological processes and targets <i>SMAD4</i>, a crucial component in hair follicle development. Tissue expression profiling revealed significant differences in <i>miR-370-3p</i> levels between skin tissues of the two sheep breeds in January and October, as well as between tissues of the Xinji fine-wool sheep and Small-tail Han sheep. <i>SMAD4</i> exhibited significant differences in tissue-specific expression in the heart, spleen, skin, lungs, and muscles from Xinji fine-wool sheep and Small-tail Han sheep. Bioinformatics analysis and dual-luciferase reporter assays validated the regulatory interaction between <i>miR-370-3p</i> and <i>SMAD4</i>. CCK-8 experiments demonstrated that <i>miR-370-3p</i>'s targeting of <i>SMAD4</i> suppressed cell growth. Cell cycle analysis demonstrated that <i>miR-370-3p</i>'s targeting of <i>SMAD4</i> influenced the cell cycle. Annexin V-FITC/PI dual labeling demonstrated that <i>miR-370-3p</i>'s targeting of <i>SMAD4</i> promoted cell apoptosis. RT-qPCR data demonstrated that <i>miR-370-3p</i>'s targeting of <i>SMAD4</i> elevated the expression of <i>JUN</i>, <i>c-MYC</i>, and <i>TCF7L2</i> while suppressing β-catenin expression. Western blot (WB) analysis demonstrated that <i>miR-370-3p</i> targeting of <i>SMAD4</i> significantly promoted c-MYC expression while inhibiting CCND1, CCND2, and β-catenin expression. <i>miR-370-3p</i> and <i>SMAD4</i> exhibit spatiotemporal expression differences in sheep skin tissues, with widespread expression across various tissues. Furthermore, it confirmed that <i>miR-370-3p</i> targets <i>SMAD4</i> to inhibit follicular papilla cell proliferation, promote apoptosis, and influence the cell cycle.