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. 2021 Dec 10:9:713840.
doi: 10.3389/fbioe.2021.713840. eCollection 2021.

Euglena gracilis and Its Aqueous Extract Constructed With Chitosan-Hyaluronic Acid Hydrogel Facilitate Cutaneous Wound Healing in Mice Without Inducing Excessive Inflammatory Response

Jin Li  1   2   3 , Zezhou Zheng  1 , Ming Du  1 , Jinchun Chen  4 , Hui Zhu  3 , Zhangli Hu  1   2 , Yanxia Zhu  4 , Jiangxin Wang  1
Affiliations

Euglena gracilis and Its Aqueous Extract Constructed With Chitosan-Hyaluronic Acid Hydrogel Facilitate Cutaneous Wound Healing in Mice Without Inducing Excessive Inflammatory Response

Jin Li et al. Front Bioeng Biotechnol. .

Abstract

Naturally occurring compounds isolated from the microalga Euglena gracilis, such as polysaccharide paramylon, exhibit antimicrobial, anti-viral, antitumor, and anti-inflammatory activities. Whether live E. gracilis cells and its aqueous extract accelerate burn wound healing remains to be investigated. In this study, live E. gracilis cells and its aqueous extract were mixed with chitosan-hyaluronic acid hydrogel (CS/HA) to form cell + CS/HA and extract + CS/HA, which were then smeared onto the deeply burned skin of mice. The efficacy of these mixtures in accelerating wound healing was assessed through wound size reduction measurement, histological and immunofluorescence analyses, and serum pro-inflammatory cytokine level (INF-γ, IL-1β, and IL-6) determination. The live E. gracilis cells and its aqueous extract were found to facilitate wound healing by enhancing re-epithelization and reducing fibroplasia without stimulating excessive inflammatory response. In conclusion, live E. gracilis cells and its aqueous extract can be potentially used to treat cutaneous wounds.

Keywords: aqueous extract; chitosan-hyaluronic acid hydrogel; live Euglena gracilis cells; microalgal therapeutics; wound healing.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Macroscopic appearance of wounds treated with CS/HA, extract + CS/HA, and cell + CS/HA at 1, 7, and 14 days in the mice. (A–C) Untreated (n = 1). (D–F) CS/HA (n = 7). (H–J) Extract + CS/HA (n = 7). (K, L) Cell + CS/HA (n = 7). Scale bar = 1 cm.
FIGURE 2
FIGURE 2
Comparison of wound size reduction among CS/HA, extract + CS/HA, and cell + CS/HA treatments at 14 days post-wounding. Wound size reduction was significantly greater in extract + CS/HA and cell + CS/HA. Significant difference compared to CS/HA. *p < 0.05, **p < 0.01. n = 14 per group.
FIGURE 3
FIGURE 3
Representative H&E-stained images of wound sections and comparison of scar length among wounds treated with CS/HA, cell + CS/HA, and extract + CS/HA at 14 days post-wounding. (A) Representative images of H&E-stained wound sections. Black double-headed arrows indicate the edges of scars. G: CS/HA; EC: extract + CS/HA; GC: cell + CS/HA. Scale bar = 500 μm. (B) Comparison of scar length after H&E staining. Wounds treated with extract + CS/HA had significantly narrower scar length than those treated with cell + CS/HA and CS/HA. Significant difference compared to CS/HA. *p < 0.05, **p < 0.01. n = 7 per group.
FIGURE 4
FIGURE 4
The representative Masson’s trichrome images of untreated group (n = 1) (A), CS/HA (n = 7) (B), extract + CS/HA (n = 7) (C), and cell + CS/HA (n = 7) (D). Wound tissue was stained with Masson’s trichrome to access collagen content and organization at 14 days post-wounding. Scale bar: 200 μm (top) or 10 μm (bottom).
FIGURE 5
FIGURE 5
H&E- and Masson’s trichrome-stained images of wounds treated with CS/HA, extract + CS/HA, and cell + CS/HA at 14 days post-wounding. (A) Untreated tissue. (B) CS/HA. (C,D) Extract + CS/HA. (E,F) Cell + CS/HA. Scale bar = 200 μm.
FIGURE 6
FIGURE 6
Comparison of INF-γ and IL-1β levels among wounds treated with CS/HA, extract + CS/HA, and cell + CS/HA at 14 days post-wounding. No notable changes in INF-γ and IL-1β levels in the mice treated with cell + CS/HA and extract + CS/HA.
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