Metabolic extract of Fusarium oxysporum induces histopathologic alterations and apoptosis in the skin of Wistar rats.

Background: Most patients with Fusarium infection present with affection of the tegumentary system, with the presence of necrotic and/or inflammatory lesions associated with pain.

Aim: To evaluate the effect of the intradermal application of a metabolic extract of Fusarium oxysporum in the skin of Wistar rats.

Methods: The extract was obtained from fungal cultivation in Czapek-Dox medium. It was sterilized by filtration through a Millipore membrane, and injected (0.5 mg/mL) intradermally into the skin of rats, which were killed 3, 6, 12, and 24 h after inoculation. Skin specimens were placed in paraffin and stained using hematoxylin and eosin, and toluidine blue, for the evaluation of the inflammatory response, and Sirius red for the quantification of collagen. Terminal deoxynucleotidyl transferase-mediated UTP nick end labelling (TUNEL) was used for the identification of apoptosis. Tissue reactions were graded and compared over time and compartment.

Results: The inflammatory reaction reached a peak at 12 h for both the dermis and subcutaneous region, being graded as moderate and moderate to severe, respectively. There was an influx of granulocytes, lymphocytes, and macrophages. A significant increase in the number of mast cells, as well as the presence of hyperemic vessels and apoptotic bodies, was observed. There was TUNEL staining in keratinocytes, fibroblasts, endothelial cells, muscles, and in the cells of the inflammatory infiltrate. There was a significant decrease in the area occupied by collagen after 12 h.

Conclusions: The extract induced histopathologic alterations in the skin, probably as a result of the presence of active toxic metabolites.