Desmin expression in fibroblasts of murine periovular granuloma during liver Schistosoma mansoni infection

We have studied the expression of the desmin gene, a muscle-specific intermediate filament protein in the granuloma cells of mouse liver infected with Schistosoma mansoni. In situ hybridization using a desmin DNA probe showed that fibroblastic cells in the granuloma strongly expressed desmin mRNAs, while in normal liver these cells did not express this mRNA to a detectable degree. The quantitative analysis of total RNAs demonstrated that the proportion of specific desmin mRNA increased from 14 to 18 weeks after infection and decreased at 20 weeks. The analysis of collagen gene expression indicated that the amount of type III collagen mRNAs was still increasing after 18 weeks from infection; in contrast, the amount of type I collagen mRNAs remained unchanged at that stage. A good correlation was observed between the detection of the specific mRNAs and the detection of both desmin and collagen molecules. Therefore, these data point to a coordinate induction of desmin and collagen gene expression during Schistosomal granuloma formation. They also suggest that the expression of the myofibroblast phenotype involves the induction of both genes.