Figure 4: Shows representative pictures of the tissue reaction to the BEGO Collagen Fleece (CFM) within the subcutaneous connective tissue (CT). A) Shows the tissue reaction at day 3 after implantation. Single mononuclear cells (arrow heads) were adherent on both sides of the fleece (CFM) while only few cells have started to penetrate the fleece body (arrows) (H & E-staining, 400x magnification, scale bar = 10 μm). B) Shows the tissue reaction at day 10 after implantation. A compact cell-rich layer of macrophages (arrow heads) was located at the material-tissue-interface, while also at this time point only few mononuclear cells (arrows) were detectable within membranes body (F4/80- immunostaining, 400x magnification, scale bar = 10 μm). C) Shows the tissue reaction at day 15 after implantation. At this time point a fiber-rich layer was located at the material-tissue interface that contained mostly mononuclear cells (black arrow heads) but also a few multinucleated giant cells (red arrow heads). Furthermore, a higher amount of mononucleated cells (arrows) was detectable within the fleece body. Additionally, the gaps between the single collagen fibers of the fleece were now filled up by fibers of the murine connective tissue (asterisk) as a sign of materials integration (Movat´s Pentachrome-staining, 400x magnification, scale bar = 10 μm). D) Shows the tissue reaction at day 30 after implantation. At this time point the fleece showed signs of integrity reduction, which was expressed by allowing the invasion of connective tissue cords (yellow asterisks). Mono- and multinucleated giant cells (arrows / red arrow heads) infiltrated the fleece (Azan-staining, 400x magnification, scale bar = 10 μm). E) Shows multinucleated giant cells (red arrow heads) in close location to (micro-) vessels (green arrows) at the peripheral region of the collagen fleece at day 30 after implantation (mononuclear cells = black arrows), (CD31-immunostaining, 400x magnification, scale bar = 10 μm). F) Shows the tissue reaction at day 60 after implantation. At this time point only small fragments of the collagen fleece were detectable within the subcutaneous connective tissue (CT). Only mononuclear cells (black arrows) and single small vessels (green arrows) infiltrated these islands (H & E-staining, 400x magnification, scale bar = 10 μm).