关键词: 多房棘球蚴, 血管内皮生长因子A, 微血管密度, 血管新生

Abstract:

Objective To investigate the relationship between angiogenesis and disease progression in hepatic Echinococcus multilocularis (Em) in mice. Methods Total 60 C57BL/6 female mice with 6-8 weeks old were randomly divided into two groups: the experimental group and the control group with 30 for each. Each mouse in the experimental group was infected by direct injection into liver with 100 μl of suspension containing 400 Em protoscoleces under anesthesia of 5% chloral hydrate. In the control group mice were injected with the same volume of PBS. Some of mice were euthanized and the liver blood vessel was filled with silicone to show the distribution of blood vessels and angiogenesis 30 d, 60 d, 90 d and 120 d after infection. The vascular endothelial cell growth factor A (VEGFA) in the sera of mice were measured by ELISA. The mouse livers were collected and subjected to hematoxylin and eosin (HE) staining for observing pathological changes. The dynamic changes of VEGFA, CD31 and CD34 expression in infected liver was analyzed by immunohistochemical staining. Results The liver blood vessel filled with silicone showed that Em gradually grew in the livers of mice, surrounded by the increased blood vessels as the infection continued in the experimental group. The levels of VEGFA in the sera of infected mice were 269.00 pg/ml at 30 d, 420.62 pg/ml at 60 d, 539.00 pg/ml at 90 d and 271.73 pg/ml at 120 d after infection, which were significant higher than that in un-infected control mice (194.00 pg/ml at 30 d, 173.00 pg/ml at 60 d, 234.00 pg/ml at 90 d and 127.00 pg/ml at 120 d after infection) with statistical difference (P < 0.05). HE staining of infected liver tissue demonstrated that the growing Em tissue surrounded by the filtration of eosinophils, granuloma and fibrosis. The protoscoleces and calcification could be observed in the middle of the lesion. Immunohistochemical staining demonstrated different degrees of expression of VEGFA, CD34 and CD31 in the endothelial cells of Em tissue. The VEGFA immunohistochemical scores of Em tissues were 1.60 ± 0.52 at 30 d, 3.10 ± 0.87 at 60 d, 4.80 ± 1.32 at 90 d and 2.40 ± 1.07 at 120 d after infection, which were significant higher than that in the surrounding normal liver tissue of infected mice or livers of control mice (0) (P < 0.01). Among the infected mice, the VEGFA immunohistochemical scores at 60 d and 90 d were significant higher than that at 30 d after infection (P < 0.05, P < 0.01, respectively). The expression of CD34-MVD in the Em tissues were 38.70 ± 11.06 at 30 d, 65.50 ± 8.46 at 60 d, 109.90 ± 9.40 at 90 d, and 56.86 ± 6.64 at 120 d after infection, which were significant higher than those expressed in normal liver cells (P < 0.01). The expression of CD34-MVD at the different time of infection was also significantly different (P < 0.01). Expression of CD31-MVD in the Em tissues were 19.80 ± 3.12 at 30 d, 30.70 ± 2.50 at 60 d, 47.90 ± 4.77 at 90 d and 31.10 ± 3.84 at 120 d after infection with significant difference among different infection time points (P < 0.01), but significant lower than that expressed in normal liver tissues (P < 0.01). Conclusion E. multilocularis invasively grows in infected liver along with significant angiogenesis and expression of CD31 possibly due to the stimulated secretion of VEGFA. The secretion of VEGFA stimulated angiogenesis, neovascularization induced by Em infection in liver of mouse.

Key words: Echinococcus multilocularis, Vascular endothelial cell growth factor A, Microvessel density, Angiogenesis