Hypoxia Preconditioned Serum (HPS)-Hydrogel Can Accelerate Dermal Wound Healing in Mice—An In Vivo Pilot Study

The ability to use the body’s resources to promote wound repair is increasingly becoming an interesting area of regenerative medicine research. Here, we tested the effect of topical application of blood-derived hypoxia preconditioned serum (HPS) on wound healing in a murine wound model. Alginate hydrogels loaded with two different HPS concentrations (10 and 40%) were applied topically on full-thickness wounds created on the back of immunocompromised mice. We achieved a significant dose-dependent wound area reduction after 5 days in HPS-treated groups compared with no treatment (NT). On average, both HPS-10% and HPS-40% -treated wounds healed 1.4 days faster than NT. Healed tissue samples were investigated on post-operative day 15 (POD 15) by immunohistology and showed an increase in lymphatic vessels (LYVE-1) up to 45% with HPS-40% application, while at this stage, vascularization (CD31) was comparable in the HPS-treated and NT groups. Furthermore, the expression of proliferation marker Ki67 was greater on POD 15 in the NT-group compared to HPS-treated groups, in accordance with the earlier completion of wound healing observed in the latter. Collagen deposition was similar in all groups, indicating lack of scar tissue hypertrophy as a result of HPS-hydrogel treatment. These findings show that topical HPS application is safe and can accelerate dermal wound healing in mice.

Immunologic Roles of Hyaluronan in Dermal Wound Healing

Hyaluronic acid (HA), a glycosaminoglycan ubiquitous in the skin, has come into the limelight in recent years for its role in facilitating dermal wound healing. Specifically, HA’s length of linearly repeating disaccharides—in other words, its molecular weight (MW)—determines its effects. High molecular weight (HMW)-HA serves an immunosuppressive and anti-inflammatory role, whereas low molecular weight (LMW)-HA contributes to immunostimulation and thus inflammation. During the inflammatory stage of tissue repair, direct and indirect interactions between HA and the innate and adaptive immune systems are of particular interest for their long-lasting impact on wound repair. This review seeks to synthesize the literature on wound healing with a focus on HA’s involvement in the immune subsystems.

Effect of Pulsed 810 nm Laser Photobiomodulation on Dermal Wound Healing and Oxidative Stress in Immunosuppressed Rats

Under immunosuppression, the sequential overlapping wound repair phases get hampered due to dysregulated or persistent inflammation leading to non-healing chronic wounds formation. The present study investigates the effect of low-power 810 nm diode laser (70 mW mean output power; 40 mW/cm2 average irradiance; 24 J/cm2 total fluence; 10 Hz pulse frequency; duty cycle 50 per cent; 10 min. illumination time once daily for seven days) photobiomodulation (PBM) on dermal penetration ability, wound healing and oxidative stress in hydrocortisone-induced immunosuppressed rats. The results of the penetration ability of 810 nm laser irradiation to the depth of the sub-dermal region revealed that the transmitted power of laser at 10 Hz pulsed-mode was better and easier than continuous-mode. The present findings clearly delineated that PBM with 810 nm laser at 10 Hz significantly augmented healing and reduced oxidative stress as evidenced by decreased free radicals, nitric oxide (NO) levels, enhanced superoxide dismutase (SOD) enzyme activity and wound area contraction facilitating the cellular redox homeostasis and promoting the tissue repair process. In conclusion, PBM with NIR 810 nm laser at pulsed-mode 10 Hz frequency showed better penetration and accelerated dermal wound healing in immunosuppressed rats.

Spatially heterogeneous epidermal growth factor release from microporous annealed particle (MAP) hydrogel for improved wound closure

We present lyophilized heparin microgels which can be directly rehydrated with epidermal growth factor and mixed with PEG microgels to form heterogenous MAP scaffolds. These EGF-releasing MAP scaffolds promote accelerated dermal wound healing.