## 3 Results  
Cutaneous wound healing was studied employing a mouse ear pinna model in healthy and diabetic animals. Forty-seven animals--24 non-diabetic and 23 diabetic--were included in the analysis. The premature death of one diabetic mouse led to the reduction of the group size (\(n=5\)) in the chitosan hydrogel treatment group. To minimize wound contraction, a donut-shaped splint was sutured to the pinna with a nylon thread through six equidistant holes. Figure 2 shows an example photograph of the wound splinting with the wound at the center of the circular opening of the splint. Angiographic OCT imaging was performed before and immediately after wounding and on five additional time points within the next 18 days. Example OCT angiograms from one non-diabetic (Figure 3a) and one diabetic mouse (Figure 3b) acquired at the different time points of the study are given in Figure 3. The top left image in Figure 3a was acquired at baseline before wounding, while the subsequent images present the angiograms immediately after wounding and 1, 4, 7, 12, and 18 days later. The circular measurement area defined by the donut-shaped ring can be easily recognized in each of the angiograms. In Figure 3b, the same timeline is depicted for the wound healing in a diabetic animal. Images provide a clear visualization of the vascular network in the mouse pinna with vessels in a size range between 20 In the angiograms shown in Figure 3a,b, various vessels of different diameters are visible within the open circular area provided by the plastic ring. The top left image (BL) shows the baseline measurement before wounding. In the next image (D00) acquired  
Figure 3: Optical coherence tomography angiography of dermal wound healing. Images present the angiogram time series of (**a**) one non-diabetic and (**b**) one diabetic animal. While the depicted non-diabetic mouse belonged to the control group that received no treatment, the diabetic animal received fibrin sealant at each study day directly after OCT measurements. BL is the baseline measurement before and D00 the measurement directly after wounding. D01 to D18 denote the angiograms acquired on the following days until the last study day 18. Figure 2: Wound splinting in the mouse ear pinna wound model. immediately after wounding, most of the vessels outside the wound area can be recognized when compared with the baseline image. At the wound site at the center, however, many predominantly small vessels belonging to the upper removed skin layers are missing. Instead, OCTA signals of deeper-lying vessels previously not visible can be seen. When comparing the image directly after wounding (D00) with the next image one day later (D01), formation of anastomoses to restore blood circulation can be observed. Images in the following days (D04 to D18) show a fine network of small vessels of various orientation formed at the wound margin and slowly closing in on the wound area. The wound site itself reveals only a weak OCTA signal that arises from vessels in deeper layers and is excluded from the calculation of the vascular parameters. The OCT angiograms were processed in order to analyze the vascular network of the investigated tissue region. Figure 4 depicts the vascular network derived from the OCT angiograms shown in Figure 3a. Here, vessels are shown in unicolor grey and the non-vessel background is black. A thin white line at the center of the vessels indicates the network graph, with red dots highlighting bifurcations. Comparison of the vessel network parameters derived from OCTA measurements performed on the first study day before wounding revealed no significant difference between non-diabetic and diabetic animals. Data are summarized in Table 2.  
Figure 5a,b show the vessel density in the ears of both non-diabetic and diabetic mice and the different study groups. In non-diabetic animals, vessel density significantly increased in the first days (D4 to D7) after wounding by 28% (fibrin group) to 45% (VEGF/PDGF group) (\(p<0.02\) for all groups). Thereafter, measured values decreased again.