Remodelling of collagen fibers has been described during every phase of cancer genesis and progression. Changes in morphology and organization of collagen fibers contribute to the formation of microenvironment that favors cancer progression and development of metastasis. However, there are only few data about remodelling of collagen fibers in healthy looking mucosa distant from the cancer. Using SHG imaging, electron microscopy and specialized softwares (CT-FIRE, CurveAlign and FiberFit), we objectively visualized and quantified changes in morphology and organization of collagen fibers and investigated possible causes of collagen remodelling (change in syntheses, degradation and collagen cross-linking) in the colon mucosa 10 cm and 20 cm away from the cancer in comparison with healthy mucosa. We showed that in the lamina propria this far from the colon cancer, there were changes in collagen architecture (width, straightness, alignment of collagen fibers and collagen molecules inside fibers), increased representation of myofibroblasts and increase expression of collagen-remodelling enzymes (LOX and MMP2). Thus, the changes in organization of collagen fibers, which were already described in the cancer microenvironment, also exist in the mucosa far from the cancer, but smaller in magnitude. Extracellular matrix (ECM) is no longer considered as an inert substrate, a three-dimensional network which only "fills the spaces" between cells and provide mechanical support 1,2. Today, ECM is known to be a complex and dynamic structure, whose chemical and biophysical properties affect cell adhesion 3 , proliferation 4 morphology 5 , migration 6 , regulate tissue morphogenesis 7,8 and fluid volume in tissues 9. The most abundant component of ECM in the lamina propria of the colon mucosa is type I collagen. Remodelling of collagen fibers has been described in almost every solid cancer, including colorectal cancer. During tumor formation and progression, collagen remodelling is constantly carried out: degradation, synthesis, cross-linking of fibers, change of fiber orientation, and interaction of cells of the innate and acquired immune system with collagen fibers 10,11. Changes in morphology, representation, and organization of collagen fibers contribute to the formation of the microenvironment that favors tumor progression, primarily through its effect on cell migration and polarization 12. Also, remodelling of collagen fibers on premetastatic sites is of great importance in determination of survival and growth of disseminated cancer cells, and thus, formation of metastasis 13,14. Remodelling of collagen fibers may be a result of changes in synthesis, degradation or cross-linking. Main cells responsible for synthesis of collagen in colon mucosa are fibroblasts and myofibroblasts. The most important enzymes for degradation of collagen fibers are matrix metalloproteinases (MMPs). It has been shown that expression of MMP2 and MMP9 is increased in colorectal cancer and influences its progression and

The spleen is the only blood filter in the organism which removes foreign antigens and effete cells from circulation. The significant role in capturing, transporting and presentation of antigens to immune cells is executed by a special subset of splenic macrophages called marginal metallophilic macrophages. Upon stimulation with lipopolysaccharide, these cells promptly migrate from their preferential location at the inner aspect of the splenic marginal sinus into the B-cell lymphoid follicles. This migration is executed via CXC chemokine ligand 13 in a lymphotoxin-dependent fashion. However, the role of tumour necrosis factor-α/tumour necrosis factor receptor-1 signalling axis has not been studied, despite its critical role in the formation of B-cell lymphoid follicles, follicular dendritic cell networks and germinal centres. Here, we show that signalling via tumour necrosis factor receptor-1 is not required for the migration of marginal metallophilic macrophages into the B-cell zone and that the presence of organized B-cell lymphoid follicles is not a prerequisite for their dislocation.