Human schistosomiasis develops
extensive and dense fibrosis in portal space, together with congested new blood
vessels. This study demonstrates that
Calomys callosus
infected
with
Schistosoma mansoni
also develops fibrovascular lesions,
which are found in intestinal subserosa. Animals were percutaneously infected
with 70 cercariae and necropsied at 42, 45, 55, 80, 90 and 160 days after infection.
Intestinal sections were stained for brightfield, polarization microscopy, confocal
laser scanning, transmission and scanning electron microscopies. Immunohistological
analysis was also performed and some nodules were aseptically collected for cell
culture.
Numerous intestinal nodules, appearing from 55 up to 160 days after infection,
were localized at the interface between external muscular layer and intestinal
serosa, consisting of fibrovascular tissue forming a shell about central granuloma(s).
Intranodular new vessels were derived from the vasculature of the external vascular
layer and were positive for laminin, chondroitin-sulfate, smooth muscle alpha-actin
and FVIII-RA. Fibroblastic cells and extracellular matrix components (collagens
I, III and VI, fibronectin and tenascin) comprised the stroma. Intermixed with
the fibroblasts and vessels there were variable number of eosinophils, macrophages
and haemorrhagic foci.
In conclusion, the nodules constitute an excellent and accessible model to study
fibrogenesis and angiogenesis, dependent on
S. mansoni eggs. The fibrogenic
activity is fibroblastic and not myofibroblastic-dependent. The angiogenesis is
so prominent that causes haemorrhagic ascites.
