title: THE ROLE OF B1 METHYLATION, PHYSIOLOGIC REPLICATION INDEPENDENT ENDOGENOUS DNA DOUBLE STRAND BREAKS (PHY-RIND-EDSB) AND LAMININ 511 E8 PROTEINS IN RAT SECOND DEGREE BURN WOUND HEALING
Creators: name: Meevassana, Jiraroch
Publisher: name: University of Liverpool Repository
Year: 2022

description: Background: The rate of re-epithelialisation is a primary determinant of the morbidity and mortality in patients with severe burn injuries. Alu elements are retrotransposons associated with epigenetic modifications. DNA methylation via short interspersed nuclear element (SINE) small interfering (si)RNA prevents DNA damage and promotes cell proliferation. Furthermore, laminin α5 β1 γ1(LM511) is an extracellular structural protein that can support epithelial cell adhesion and migration. Box A of high-mobility group box 1 protein (Box A of HMGB1), a component of high mobility group (HMG) family of non-histone proteins, is a common nuclear protein in eukaryotic cells that can reduce DNA damage response toward burn injury. Therefore, SINE siRNA, LM511and Box A of HMGB1 may be able to promote burn wound healing. Here, a SINE B1 siRNA was used to treat burn wounds in rats. Objective: To investigate whether treatment of burn wounds using B1 siRNA, Box A of High-mobility group box 1 protein (Box A of HMGB1) and LM511-E8 fragment improved wound closure in a rat second-degree burn wound model. Methods: I performed a cross-sectional analytical study using tissue and blood samples from post-burn and healthy patients (N = 23 each) to measure Alu methylation levels and patterns. The results of the combined bisulfite restriction analyses were categorised into four groups based on the methylation status at the CpG dinucleotides from the 5′ to 3′ ends of the Alu sequence: hypermethylated (mCmC), hypomethylated (uCuC), and partially methylated (uCmC and mCuC). In in vivo experiments, second-degree burn wounds were introduced on the backs of rats. The rats were then divided into control and experiment groups: a B1 siRNA-treated, Box A of HMGB1 protein and LM511-E8, saline-treated control, and calcium phosphate-nanoparticle-treated control group (N = 15–20/group). The wounds were imaged on days 0, 7, 14, 21, and 28 post-injuries. The tissue sections were processed for methylation and histological and immunohistochemical examination and scored based on the overall expression of histone H2AX phosphorylated on serine 139 (γH2AX), 8-hydroxy-2′-deoxyguanosine (8-OHdG), and presence of cytokeratin 10 and 14. Results: Alu methylation levels were lower in hypertrophic scar tissues than in normal skin (29.4 ± 2.5% vs. 35.6± 3.2%, P = 0.0002). Receiver operating characteristic analysis indicated that the uCmC and uCuC patterns were useful as post burn hypertrophic scar DNA methylation markers, with 91.3% sensitivity and 96.2% specificity and 100% sensitivity and 94.2% specificity, respectively. Burn wound closure improved in the B1 siRNA-treated group compared to that in the control group, especially from days 14 to 28 post-injury (P &lt; 0.001). The overall pathological score and degree of B1 methylation in the B1 siRNA-treated group improved at days 14–28 days post-injury, with the maximum improvement observed on day 14 (P &lt; 0.01) compared to the NSS and Ca-P nanoparticle groups. Immunohistochemical staining revealed lower expression of γH2AX and 8-OHdG in the B1 siRNA-treated group than in the control groups at days 14–28 post-injury; the maximum improvement was observed on days 14 and 21. The Box A of HMGB1 protein group demonstrated a significant improvement in burn wound closure rate, starting from day 7th until day 28th after injury, compared to the wound closure rate of the normal saline, scramble plasmid, and calcium-phosphate nanoparticle-treated groups, especially on days 14 to 21 (P &lt; 0.001). Furthermore, γH2AX expression in the HMGB1 plasmid-treated group was lower than that in the control group from day 7 to day 21 (P &lt; 0.05), especially on day 14 (P &lt; 0.01). The Box A of HMGB1-treated group showed lower levels of 8-OHdG in burn wounds than did the NSS-treated group from days 7 to 21 (P &lt; 0.05). Burn wound healing improved in the LM511-E8-treated group from 7–28 days post-injury (P &lt; 0.01). The re-epithelialisation in the LM511-E8-treated group was quicker than that of the control group at 7–28 days post-injury, with the largest improvement observed on days 7 and 14 (P &lt; 0.001). The overall pathological score of the LM511-E8-treated group was higher than that of the control group at 14–28 days post-injury; maximum improvement was observed on days 14 and 21. Conclusion: These results imply that LM511-E8 fragment, B1 siRNA, and Box A of High-mobility group box 1 protein (Box A of HMGB1) are promising therapeutic options for managing second-degree burns. Moreover, these findings suggest that epigenetic modifications play a major role in hypertrophic scar pathogenesis and may be the starting point for developing a novel strategy for burn scar treatment.