Effect of overwork on hemopoietic function of spleen in mice

Abstract

Objective To investigate the effect of overwork on the hemopoietic function of spleen in mice. Methods A total of 18 C57BL/6J mice were randomly divided into 3 groups, i.e., control group (C), 15-day-overworked group (W1) and 30-day-overworked group (W2). The mice from Groups W1 and W2 were forced to keep standing in water for 8 h and restrained for 3 h for consecutive 15 and 30 d, respectively, while those of Group C had no special treatment. The general condition, food intake and body weight of the mice were observed and measured. After modelling, the mice were euthanatized, and the spleen and heart were isolated to calculate spleen index and observe spleen pathological changes after HE staining, and then blood routine test was performed. The mRNA expression levels of CXCL12 and SCF in the spleen and that of connexin 45 (Cx45) in the heart were detected by RT-qPCR, and the protein levels of CXCL12 and SCF in spleen were detected by ELISA. The cardiac protein level of Cx45 was quantified with immunohistochemical assay. Results ① General condition showed that Groups W1 and W2 showed coarse hairs, increased at first and then decreased in activities, poor mental state, and larger food intake when compared with Group C. The body weight of Group C was increased with the feeding time, but that of Groups W1 and W2 had no such change. The spleen index was decreased significantly in Group W2 (P < 0.05). ② The results of blood routine test showed that WBC and RBC counts and HGB level were significantly increased in Group W2(P < 0.05), and PLT count in Groups W1 and W2 was significantly increased compared with Group C (P < 0.05). ③ Spleen HE staining displayed that the boundary between red pulp and white pulp was not clear, and the region of red pulp was enlarged in Group W2 when compared with Group C. ④ RT-qPCR showed that the mRNA level of Cx45 was significantly higher in heart tissue of Group W2 than that of Group C (P < 0.05), and that of SCF in spleen tissue of Group W2 was also higher than that in Groups C and W1 (P < 0.05). ⑤ Immunohistochemical assay indicated that the protein expression of Cx45 in myocardium of Groups W1 and W2 was significantly higher than that in Group C (P < 0.05). ⑥ ELISA revealed that the content of SCF in the spleen of Group W2 was notably higher than that of Groups C and W1 (P < 0.05), but there was no statistical difference between Groups W1 and C. Conclusion Overwork destroys the tight connection between cardiac myocytes, enhances the hemopoietic function of spleen, increases WBC count, and then forms a hypercoagulable state, which may be one of the precipitating factors for cardiovascular diseases related to overwork.

Keywords

• overwork
• extramedullary hematopoiesis
• spleen
• myocardial infarction