EXPRESSION OF VASCULAR ENDOTHELIAL GROWTH FACTOR DURING NURSE CELL FORMATION IN Trichinella spiralis AND Trichinella pseudospiralis INFECTIONS

Abstract

The two most common Trichinella species causing human disease are T. spiralis and T. pseudospiralis belonging to encapsulated and non-encapsulated clades, respectively. Upon invasion, the larva of T. spiralis not only occupies and develops inside the muscle cell but also transforms it into a nurse cell surrounded by the vascular network called circulatory rete. It has been postulated that vascular endothelial growth factor (VEGF) is involved in the rete formation leading to the development and maintenance of nurse cell. This study showed that the expression of VEGF in the nurse cell of T. spiralis and T. pseudospiralis was detected by in situ hybridization. Basal expression of VEGF was found in uninfected muscle by real-time PCR technique and Western blot analysis. Nevertheless, both methods were not able to demonstrate the increase of VEGF expression above the basal expression in muscles infected with T. spiralis or T. pseudospiralis. The unexpected results are probably due to the relatively small number of infected nurse cells which could not produce enough positive signals to show significant increase in VEGF expression. It is likely that VEGF plays a role in the formation of circulatory rete and nurse cell in T. spiralis infection. However, there has been no experiment to directly validate this hypothesis. This area of study should be further investigated.