## 4 Discussion  
This study demonstrated that during the healing of burn wounds, the content of HS in the injured tissue changes with different intensities and different dynamics, although with a similar tendency in each of the four experimental systems. It was observed, as in the case of previous experimental achievements of the co-authors of this manuscript, that from the onset of the burn injury until the 3 rd day of the healing process, there was a notable rise in the content of HS in tissues treated with nonwoven dressings containing 5% and 10% propolisis [10; 11]. However, this increase was followed by a rapid decline in the concentration of these particular GAGs, persisting until the conclusion of the experiment on day 21. Strong changes were caused by 10% propolisis. Changes in the HS content in  
Figure 2: Dynamics of changes in the content of HA in a burn wound during subsequent days of its treatment with a nonwoven dressing containing 5% propolisis: a—statistically significant difference compared to day 0 after the burn (\(p<0.001\)), b—statistically significant difference in relation to the 3 rd day after the burn (\(p<0.001\)), c—statistically significant difference in relation to the 5 th day after the burn (\(p<0.001\)), d—statistically significant difference in relation to the 10 th day after the burn (\(p<0.001\)), e—statistically significant difference compared to day 0 after the burn (\(p<0.05\)), f—statistically significant difference in relation to the 10 th day after the burn (\(p<0.01\)). Differences in the content of HA in post-burn wounds in the following days after the exposure to the thermal factor, depending on the wound dressing method used: g—statistically significant difference in the HA content in the wound treated with a nonwoven dressing containing 5% propolisis, compared to the wound treated with NaCl solution, on the same day of the experiment (\(p<0.001\)), h—statistically significant difference in the HA content in the wound treated with a nonwoven dressing containing 10% propolisis, compared to the wound treated with NaCl solution, on the same day of the experiment (\(p<0.001\)), i—statistically significant difference in the HA content in the wound treated with a nonwoven dressing without propolisis compared to the wound treated with NaCl solution, on the same day of the experiment (\(p<0.001\)). wounds treated with nonwoven dressings not containing propolis or treated with sodium chloride were characterized by convergent trends and dynamics. The findings from this study regarding the fluctuation in heparan sulfate content, specifically a transient increase observed in the ECM of the wound, align with the phenomenon described by [PERSON] et al. [54]. This phenomenon, characterized by a transient increase in HSPG (heparan sulfate proteoglycan) expression during tissue repair, was similarly noted in our study and was particularly evident when treating burn wounds with polymer nanofibers infused with 5% and 10% propolis. The cited authors used mesoglycan--consisting of GAGs (including HS)--to examine its effect on the repair of tissue damage. The above-mentioned authors observed a significant relationship between the migration of keratinocytes and fibroblasts during the healing of venous ulcers and the content of GAGs in the wound bed. The described studies indicated the involvement of HS in the course of repair phenomenon, throughout the orchestration of the movement, growth, division and specialization of cells initiating inflammatory responses and cells synthesizing ECM particles, as well as those playing a key role in repepithelialisation [54, 55]. Studies by [PERSON] et al. [10] also showed (visible in the first three days after the burn) a short-term increase in the content of HS in the bed of burn wounds treated with propolisis, which confirmed the beneficial effect of the mentioned compound of natural origin on the tissue repair process. The initial increase in HS content is crucial in the early stages of wound healing. After injury, HSPGs are degraded by heparanases [10, 56].