## 4 Discussion
The cited studies showed that in the initial phase of the experiment, there was an increase in the HA content in the wound bed treated with an ointment containing propolisis and then--in the final phase--a decrease in the HA content. The observed tendency of HA content changes can be explained by the bee glue-stimulated enhanced biosynthesis of transforming growth factor-beta modulating the fibroblasts to produce the non-sulfated glycosaminoglycan [11]. The glycan in question is a compound abundantly present in the wound environment. It has been shown that HA is intensively synthesized by fibroblasts in the initial period of healing (for about 2 weeks from the moment of injury) and then--in the final phase of tissue healing--the content of this GAG in the wound bed is reduced [58]. HA can bind to specific proteins that are surface receptors of ECM cells. The most frequently described cell surface receptors include CD44, RHAMM (receptor for HA mediated motility), and ICAM-1. CD44 glycoprotein mediates the processes of migration, aggregation, cell adhesion and proliferation, angiogenesis, cell signaling, and the degradation of HA; RHAMM mediates cell migration and proliferation, while ICAM-1 is involved in the activation of inflammatory processes [63]. The nonsulfated glycan in question--functioning as a pivotal molecule in the course of connective tissue regeneration--modulates systemic reaction to infection/injury and formation of a provisional matrix (composed of fibroblasts, macrophages, and endothelial cells together with collagens and fibronectin) and resurface tissue injury by the novel epithelium formation [64; 65; 66; 67]. HA is also involved in tissue repair and serves as an integral part of the extracellular matrix, also promoting the proliferation and migration of keratinocytes in the process of reepithelialization. Keratinocyte migration is necessary to re-epithelialize the wound and to restore the continuity of damaged skin [68; 54]. [PERSON] et al. [65] found that HA and CD44 are localized in the same region of the epithelium (around mucosal keratinocytes) at all stages of human mucosal wound healing, participating in reepithelialization during the tissue repair process. The research conducted in this study demonstrated a notable positive impact of non-woven polymer dressings enriched with a natural active substance, namely propolisis, particularly at a higher concentration (10%), on the healing mechanisms of burn wounds. The latter observation may potentially be explained by the significantly increased accumulation and intensity of extractability of molecules previously referred to as mucopolysaccharide, from the matrix of experimental thermal injuries. This contrasted with the biochemical profile observed in wounds treated solely with nonwoven dressings devoid of the incorporated active substance [69; 70]. To minimize the risk of improper healing and excessive scarring, the best possible healing conditions should be ensured, which becomes possible as a result of the implementation of modern polymer dressings containing medicinal substances incorporated into therapeutic procedures [69]. As shown in this study, the use of PLGA nonwoven dressings containing propolis may prove to be an effective therapy for burn wounds [70].