The role and mechanism of miR-557 in inhibiting the differentiation and maturation of megakaryocytes in immune thrombocytopenia.

Specific miRNA in immune thrombocytopenia (ITP) was screened to explore its intervention effects and mechanisms in ITP. MTT assay and CFSE staining were used to detect the effects of gradient concentrations of thrombopoietin (TPO) on cell proliferation. Expressions of differentially expressed miRNAs were analysed via qRT-PCR in TPO-induced megakaryocytes and ITP plasma. Effects of miR-557 on cell physiological functions were examined by MTT and flow cytometry. Expressions of miR-557, apoptosis-associated genes and Akt/ERK pathways were detected by qRT-PCR and Western blot as needed. Multinucleation of TPO-induced megakaryocytes was determined by megakaryocyte colonies. The toe skin and intestinal bleeding of the ITP rat model were observed and evaluated. Effects of miR-557 on the numbers of platelets, megakaryocytes, and peripheral blood platelets and the expressions of CD4 ⁺ T cells, Treg cells, TGF-β, IL-6 and miR-557 in the ITP rats were detected by Giemsa staining, flow cytometry, ELISA and qRT-PCR. MiR-557 was identified as an specific miRNA associated with both ITP and TPO treatment. MiR-557 inhibitor enhanced the physiological functions of TPO-induced megakaryocytes, while miR-557 mimic had the opposite effect. At the molecular level, the expressions of miR-557, cleaved Caspase-3 and Bax were further silenced by inhibitor, on the contrary, the expressions of bcl-2, p-Akt and p-ERK were upregulated. Animal experiments showed that, miR-557 inhibitor increased the numbers of platelets and megakaryocytes, and improved the symptoms of ITP model rats. Our results indicated that miR-557 inhibitor improved ITP by regulating apoptosis-related genes and cellular immunity and activating the Akt/ERK pathway.