Wound healing is a complex and intricate process, yielding different outcomes based on even subtle environmental variations. Therefore, providing an ideal environment is crucial for healing.

Dressing materials, which act as barriers against external contaminants, effectively shielding the wound from microbial invasion and reducing the risk of secondary infections, play a key role in wound care [1]. The ideal material can create an optimal moisture balance around the wound site, preventing excessive dryness or moisture, both of which can impede healing. Additionally, dressings facilitate the absorption of wound exudate, the fluid that oozes from the wound, which helps maintain a clean environment conducive to healing.

By carefully selecting dressing materials that align with the specific needs of a given wound, such as size, depth, location, or type of injury, healing outcomes can be improved [1,2]. Ideally, these materials consist of biocompatible substances that prevent inflammation and rejection reactions in the wound tissue. Natural high-molecular-weight polymers, such as hyaluronic acid (HA), are preferred because of their ability to activate healing signals while maintaining a moist wound environment. HA is a glycosaminoglycan that plays a crucial role in wound healing by regulating inflammation and promoting tissue repair. Its use in dressings underscores its therapeutic benefits for optimizing the wound-healing process [3].

The present study aimed to investigate the effects of an HA-based dressing by creating full-thickness dermal wounds on the dorsal skin of rats, which is histologically similar to that of humans [4]. We compared the healing effects of HA-based dressings with those from hydrocolloid-based dressings as well as those from controls, without dressings.

Throughout the 3-week experiment, macroscopic observations revealed by approximately day 14, all of the wounds had healed, followed by wound contraction without noticeable scarring. Additionally, no complications such as infections were observed in the wound areas, and none of the subjects showed any abnormalities in their vital signs. The data were organized into tables by day for statistical analysis (Tables 2-4).

On day 3 after wound creation, significant inflammatory cell infiltration was observed in group A compared to the other groups (p= 0.045). Collagen deposition, which is indicative of extracellular matrix (ECM) formation, was also higher in group A than in the other groups (p= 0.040). On day 7 post-wound creation, while inflammatory cell infiltration remained elevated without significant differences, angiogenesis, measured by neovascularization, showed the highest values in group A, followed by group B and the control group (p= 0.011). By day 21 post-wound creation, all of the wounds had fully healed, and were filled with new epithelial cells. The thickness of the new epithelial layer, indicating the maturity of the inflammation and fibroblasts, was significantly greater in group A than the other two groups (p= 0.037). These results were prominently observed after H&E staining (Fig. 2). As shown in Fig. 2A-C, an increase in the concentration of inflammatory cells, such as neutrophils, was observed. Fig. 2B shows a higher concentration of these cells near the epidermis compared to that shown in Fig. 2A and 2C. Additionally, although inflammatory cell infiltration remained high, increased angiogenesis was seen in the surrounding area (compare Fig. 2E to Fig. 2D and 2F). Furthermore, group A shows a thicker re-epithelialization layer compared to the other groups (Fig. 2H).

The wound-healing process is a highly complex sequence of events involving overlapping stages: hemostasis, inflammation, proliferation, and maturation. Each stage relies on specific cytokines and growth factors for proper signaling and progression. Hemostasis begins with fibrin activation shortly after injury, forming blood clots that induce vasoconstriction and create a provisional matrix for inflammation. Neutrophils, monocytes, and fibroblasts migrate to the wound site during this phase to initiate healing. Inflammation persists for 2–3 days post-injury, with neutrophils playing a primary role as the first inflammatory cells to activate the complement system, target surrounding pathogens, and aid in tissue repair. Monocytes transform into macrophages within the wound bed to phagocytose dead cells and debris, while activating numerous cytokines and growth factors to facilitate creation of the ECM, fibroblasts, smooth muscle cells, and endothelial cells, preparing for the next phase. During the proliferation phase, growth factors secreted by macrophages, including fibroblast and vascular endothelial growth factors, stimulate fibroblast proliferation and angiogenesis, which are key to the subsequent granulation tissue formation and wound closure. Proteases, produced as collagen production increases, contribute to the formation of the new ECM, initiating the formation of granulation tissue approximately 5 days post-injury. Re-epithelialization begins concurrently, minimizing the area of the wound that requires recovery by inducing adjacent tissues to contract. Maturation involves apoptosis or the departure of the majority of the macrophages and fibroblasts from the wound site, while collagen fiber alignment enhances the tensile strength of the skin, aiding in restoring the skin to its pre-injury state. However, delayed or prolonged wound healing can lead to chronic wounds and an increased risk of scarring [6,7].

Dressings can accelerate the effective wound-healing process by aiding the activation of each phase when appropriately applied to the wound. Optimal wound dressings should adhere well to the damaged tissue, maintain proper moisture levels to prevent external infections [8], and be amenable to periodic replacement with reasonable cost efficiency. Because wound formation can vary widely in cause and presentation, the selection of suitable dressing materials is crucial. Ongoing development offers diverse options to maintain a moist environment, such as films, foams, hydrogels, and hydrofibers [9]. In the present study, we aimed to compare the effects of two hydrogel-based products, namely HA and hydrocolloid. Hydrogels necessitate secondary dressings enveloped with film. Additionally, a control group was included with only film dressings to eliminate potential variables from this approach.

The Duoderm hydroactive gel used in group B is a hydrogel dressing composed of natural hydrocolloids, including gelatin, pectin, and sodium carboxymethylcellulose [10]. Widely used for treating various wounds, this hydrogel is valued for its non-irritating, non-sensitizing properties, and compatibility with the pH of human skin. Additionally, the gel is sometimes used with silicone foam dressing to prevent pressure damage [11]. However, as a hydrogel, Duoderm hydroactive gel lacks strong adhesion and has a limited capacity to absorb large exudates, requiring the use of secondary dressings.

In contrast to group B, the Connettivina gel used in group A is a hydrogel dressing composed of 200 kDa low molecular weight HA, a linear polysaccharide consisting of repeated units of glucuronic acid and N-acetylglucosamine disaccharide. First discovered by Meyer and Palmer in 1934, HA has since gained attention for its abundance in the human body, particularly in the dermal layers of the skin [12]. HA is known to activate components such as macrophages, fibroblasts, and collagen, thereby facilitating the inflammatory phase. Moreover, HA promotes vascular formation and regulates wound hydration and osmoregulation [13]. Consequently, it is suitable not only for wounds caused by injury but also for maintaining scalp hydration after laser treatments or hair transplant procedures, where increased hydration is beneficial. Additionally, hyaluronidase, which can break down HA, demonstrates effectiveness in treating microstomia based on this principle [14]. However, HAbased hydrogels have drawbacks such as weak mechanical properties and rapid degradation [15], necessitating caution in their use. In this study, we compared widely used hydrocolloid-based hydrogels with HA-based hydrogels to assess their effectiveness in wound healing under similar conditions.

Visual observation alone has limitations in assessing the effectiveness of the previously mentioned processes. Instead, proper histological evaluation allows for accurate and detailed assessment by measuring essential components present in each phase. Although some studies have utilized precise and detailed quantitative scoring systems to quantify these components [16], such methods may not clearly differentiate between compared values owing to the nature of the process, thereby limiting comparability [17]. In the present study, we employed a semi-quantitative scoring system to compare the distribution of cells or vessels present in each phase of healing.

The findings of this study confirmed significant differences (p< 0.05) in several parameters among the three groups. Specifically, inflammatory cell infiltration, peaking around day 3, was notably higher in group A than in the control group and group B. Additionally, group A exhibited greater collagen deposition, suggesting that HA facilitates signaling in the dermal layer and promotes chemotaxis of surrounding inflammatory cells to the wound site [18]. Moreover, on the 7th day post-wound, during the proliferation phase, group A showed significantly higher neovascular infiltration than the other groups, attributable to HA’s known effect in promoting vascular formation [19]. Furthermore, by the 21st day, nearly all wounds showed re-epithelization, with group A demonstrating significantly higher thickness at the injury site than the other two groups, indicating accelerated tissue regeneration, potentially due to HA’s effective regulation of hydration.

Despite our promising results, this study had several limitations that warrant acknowledgment. First, we experimented on the epidermis of rats rather than human skin, necessitating further research to determine whether similar significant differences would occur in human skin. Given that the wound healing mechanism in rodents occurs through the contraction of the panniculus carnosus layer, it was noted that an 8-mm wound diameter may be restrictive for comparing healing effects. Second, the sample size was relatively small, making it challenging to generalize the findings. Future studies should expand the sample size, focusing on parameters that show statistically significant differences. Third, we were unable to perform a comparison of wound size visually using gross photos, in addition to the histological comparison. Fourth, using HA containing silver sulfadiazine instead of simple HA might have introduced a degree of error into the results. Silver sulfadiazine is a sulfa-derived antibiotic medication that operates through inhibiting the growth of bacteria. Finally, this study did not investigate wound maturation or scarring beyond the 21st day of healing. Subsequent evaluation of dermal thickness via ultrasound can be helpful in understanding the patterns of scar formation thereafter [20]. Therefore, we recommend that follow-up studies be conducted to further explore these aspects of wound recovery.

Despite various experimental and comparative studies on the wound healing effects of HA being published, this paper is valuable as we objectively compared these effects with those of a similar hydrogel type dressing product, hydrocolloid, which is widely used in our hospital. Although there are limitations to generalizing these findings, we anticipate future research to broaden the range of materials available for wound treatment. These findings highlight the potential of HA-based dressings to improve clinical outcomes in wound care, indicating opportunities for advancing therapeutic approaches.