DATING OF FIBROTIC LESIONS BY THE PICROSIRIUS-POLARIZATION METHOD - AN APPLICATION USING THE LESIONS OF LECHIGUANA (BOVINE FOCAL PROLIFERATIVE FIBROGRANULOMATOUS PANNICULITIS)

This work was designed to verify if a simple quantitative procedure to estimate the state of collagen aggregation is useful in describing th e natural history of a fibrous process. For this purpose sixteen cases of Lechiguana lesion were used. Histochemical evaluation of the colla gen content and its state of aggregation was done by the Picrosirius-p olarization method. Morphometric studies were done by means of a point -counting procedure, which allowed the determination of the areal frac tion of thin and thick collagenous fibers within Lechiguana lesions co llected at different times of clinical evolution (14 days through 8 mo nths). Early lesions are characterized by thin collagenous fibers. Thi s population of slender fibers decreases later on, when thick fibers b ecome more prevalent. Curve fitting procedures were employed using the state of collagen aggregation as the dependent variable and time as t he independent variable. The best fitting was obtained by linear and e xponential functions. Statistical analysis indicates that the quantita tive study of the degree of collagen organization allows an adequate d etermination of the time course of Lechiguana lesions. We concluded th at simple determinations of collagen aggregation provide numerical dat a that may be useful to build mathematical models relating time of evo lution of the disease to fibrosis.