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Mast cells and eosinophils actively participate in tissue repair and are prominent components of Schistosoma mansoni granulomas. Since pentoxifillyne (PTX) is an immunomodulatory and antifibrotic substance, we aimed to characterize, by morphological techniques, the effect of this drug on fibrosis developed inside murine hepatic schistosomal granulomatous reaction, beyond the quantification of eosinophil and mast cell populations. The drug (1 mg/100 g animal weight) was administrated from 35 to 90 days post-infection, when the animals were killed. The intragranulomatous interstitial collagen network was analyzed by confocal laser scanning microscopy, the number of eosinophils and mast cells was quantified and the results were validated by t-student test. Treatment did not interfere on the granuloma evolution but caused a significant decrease in the total and involutive number of hepatic granulomas (p = 0.01 and 0.001, respectively), and in the intragranulomatous accumulation of eosinophils (p = 0.0001). Otherwise, the number of mast cells was not significantly altered (p = 0.9); however, it was positively correlated with the number of granulomatous structures (r = 0.955). In conclusion, PTX does not affect development and collagen deposition in S. mansoni murine granuloma, but decreases the intragranulomatous eosinophil accumulation possibly due to its immunomodulatory capability, interfering in cellular recruitment and/or differentiation.

In vivo degradation of the extracellular matrix of Schistosoma mansoni granulomas was morphologically studied by light and electron microscopy using 60 day-infected hepatic isolated and acellular granulomas (aPMC) which had been implanted into the subcutaneous tissue of syngenic albino mice and examined 4, 15, 20, 30 and 40 days after implantation. The progressive changes of aPMCs were estimated by measurements of aPMCs surface (micron2) on paraffin sections. After implantation, polymorphonuclear leukocytes were the initial population recruited whereas macrophages and fibroblasts were prominent in the late stages. Eosinophil leukocytes and in a lesser extent, mast cells increased in number. In electron microscopy, progressive disappearance of extracellular matrix and some modified collagen fibrils either in extracellular or intracellular localization represented matricial changes. The morphometrical analysis of aPMCs of the surface (micron2) after implantation showed a significant reduction of aPMCs (p < 0.001) in all stages after implantation. Polymorphonuclear cells, macrophages and fibroblasts seemed to be the major responsible cells involved in aPMCs resorption.

Patterns of fibrosis within hepatic and intestinal granulomas of Schistosoma mansoni-infected mice were analyzed by indirect immunofluorescence. Deposition of collagen isotypes, laminin, and fibronectin was evaluated semiquantitatively between 8 and 20 weeks of the infection. Liver granulomas were the largest at 8 weeks and contained low amounts of type I and higher amounts of type III collagen and fibronectin. Collagen deposition became pronounced as infection progressed. The relative amounts of type I collagen deposits rose and equalled that of type III. In the smaller immunomodulated granulomas at 20 weeks both types I and III were high, and type IV collagen deposition was observed. Fibronectin and laminin deposits were also detected. The small ileal granulomas did not change their size during the course of the infection. At 8 weeks, connective tissue matrix deposition was barely detectable within these lesions. Gradually, small deposits of types I and III appeared in equal amounts and attained highest levels by 20 weeks of the infection. Fibronectin deposits at that time were very prominent but laminin and type IV collagen were absent. Colon granulomas at 8 weeks of the infection were only somewhat smaller than those of the liver, yet contained very sparse deposits of types I and III collagen. During the ensuing weeks collagen deposits rose only slightly. By 20 weeks the granulomas diminished in size and within those lesions type III collagen was predominant. Whereas the presence of fibronectin was pronounced, type IV collagen and laminin were detectable only in trace amounts. These observations indicate the existence of important organ-related differences in the intragranulomatous deposition of connective tissue matrix.

The connective matrix of sarcoid granulomas is polymorphic. Immunolabeling techniques show that it is partly composed of fibronectin and collagen types I and III and is found at all stages of the granulomas' evolution. This suggests that the process known as hyalinization is not due to changes in the composition of the matrix but results from a gradual accumulation of connective tissue components. Fibronectin seems to play an essential role as mediator between different cell populations during the evolution of the granulomas.

We studied collagenase, gelatinase and stromelysin syntheses by human fibroblasts cultured on three models of tridimensional matrix: native collagen sponge, native collagen complexed with glycosaminoglycans sponge, and acellular sarcoid matrix complex prepared from human sarcoid granulomas. Collagenase and stromelysin biosyntheses were differently stimulated according to culture conditions. Fibroblasts secreted a same amount of collagenase or stromelysin when cultured on collagen and collagen-glycosaminoglycans sponges, while collagenase and stromelysin secretions were widely amplified when cultured on sarcoid matrix complex. In contrast, gelatinase production was equally induced by the three culture conditions. In the different culture conditions on tridimensional matrix, the three matrix metalloproteinases were synthesized in a latent form. Thus, the sarcoid matrix complex stimulated the release of collagenase and stromelysin by fibroblast, but did not stimulate the release of gelatinase. This suggests that collagenase and stromelysin syntheses are co-regulated while gelatinase production is controlled by a distinct mechanism.