Figure 7: Shows representative pictures of the multi-stratified collagen membrane (CM) within the subcutaneous connective tissue (CT). The left row (A1-A5) shows the tissue reaction towards the compact surface layer of the membrane, while the right (B1-B5) row displays the reactions to its spongy and rough surface layer. A1) and B1) show the tissue reactions at day 3 after implantation. A multilayered wall (arrow heads) consisting of mononuclear cells was located onto the surface of the compact surface layer of the collagen membrane (A1), while only single mononuclear cells (arrows) were adherent on the spongy surface of the membrane at this early study time point (B1). Only at the membrane side with the compact layer single mononuclear cells (arrows) were detectable within the membrane body (A1) (Masson Goldner-stainings, 400x magnifications, scale bars = 10 μm). A2) and B2) show the tissue reactions to the collagen membrane at day 10 after implantation. At this time point a cell-rich peri-implant CT was detectable at the compact surface layer of the membrane. Mononuclear cells such as macrophages (black arrow heads) and single multinucleated cells (red arrow head) were located at the material´s surface. At this time point mononuclear cellular penetration (arrows) seemed to occur from mononuclear cells towards the inner region of the compact layer (A2). A wall of mononuclear cells (arrows heads) covered the spongy surface layer of the membrane (B2) (A2: F4/80-staining, B2: Sirius-staining, 400x magnification, scale bars = 10 μm). A3) and B3) show the tissue reaction to the collagen membrane at day 15 after implantation. At this time point the compact layer was covered by a high amount of multinucleated giant cells (red arrow heads) in combination with mononuclear cells (black arrow heads). Mainly single mononuclear cells (black arrows) infiltrated this membrane component (A3). In contrast, the spongy layer was covered mainly by mononuclear cells (black arrow heads), while only single multinucleated cells were detectable (red arrow head). Only single mononuclear cells (arrows) were located within the spongy membrane body at this time point (B3) (A3: Azan-staining, B3: Movat´s Pentachrome-staining, 400x magnifications, scale bars = 10 μm). A4) und B4) show the tissue reactions to the collagen membrane at day 30 after implantation. The compact layer was completely interspersed by mononuclear (black arrow heads) and multinucleated giant cells (green arrow heads) (A4). Furthermore the spongy layer was covered mainly by mononuclear cells, while only few of these cells (arrows) have started to infiltrate the membrane body at this time point (B4). (A4: Sirius-staining, B4: Azan-staining, 400x magnifications, scale bars = 10 μm). A5) and B5) show the tissue reactions to the collagen membrane at day 60 after implantation. Only a thin remnant of the compact layer (asterisk) seemed to be remaining at this late study time point. No signs of the previously observed multinucleated tissue reaction towards this membrane part were detectable and this membrane side was covered by mononuclear cells (arrow heads). Few cells have been detected penetrating into the membrane through the compact layer (arrows) (A5). The spongy layer of the membrane was furthermore mainly covered by mononuclear cells (arrow heads) and a slight tissue ingrowth was observable. Still few mononuclear cells (arrows) were locatable within membranes body (B5) (A5: Sirius-staining, B5: Azan-staining, 400x magnifications, scale bars = 10 μm).