Abstract: Objective: To investigate the influence of miR-126 knock down on the development of mouse thymocytes and explore its significance preliminarily. Methods: The volume, weight and total cells number of thymus in miR-126 knockdown (KD) mice were conventional detected. The expression of miRNA-126 in thymus also was detected by Real-time PCR. The pathologic morphology change of thymus was observed by HE staining. The proportion, as well as the expression of nuclear antigen Ki-67 and the apoptosis of lymphocytes in thymus from miR-126KD mice were determined by Flow cytometry analysis. Finally, the expression level of p-AKT and p-ERK1/2 in the thymus were detected by Western blot. Results: Compared with those of WT mice, the volume, weight and total cells number of miR-126KD mice thymus were no obvious differenced. The expression level of miRNA-126 in miR-126KD mouse thymus was significantly lower than that in the WT mice(P<0.05). Thymus morphology of miR-126KD mice was abnormal. Compared with WT mice, the percentage and absolute number of thymic CD4+ SP cells in miR-126KD mouse were increased obviously (P<0.05), however, the proportion and number of DP cells were significantly decreased(P<0.05). Furthermore, compared with that in WT mice, the expression of nuclear antigen Ki-67 in thymic CD4+ SP cells from miR-126KD mouse were abnormally increased and the apoptosis of thymic CD4+ SP cells were decreased(P<0.05); Conversely, the expression of nuclear antigen Ki-67 in DP cells were significantly decreased(P<0.05). Finally, the expression level of p-AKT and p-ERK1/2 in the thymus were decreased in miR-126 KD mice (P<0.05). Conclusion: miR-126 knock down could affect the development of thymocytes in the thymus, especially on the development of CD4+T cells, which provide an important experimental basis for further exploring the roles of miR-126 in the development and function of thymocytes.

Key words: [Key words] miR-126, knock down, thymus, CD4+ T cell