Evaluation of the effect of Matricaria recutita monotherapy or in combination with photodynamic therapy on tissue repair in the dorsum of the tongue of rats

Abstract

Objective: The search for treatments that accelerate the healing of lesions is of constant interest. Matricaria recutita (chamomile) is a plant with antimicrobial, anti-inflammatory, and healing properties, and antimicrobial Photodynamic Therapy (aPDT) eradicates microorganisms, which favors tissue repair. This study aimed to evaluate the effect of the topical use of chamomile with or without aPDT on tissue repair in rats' tongues.

Methodology: A total of 75 male Wistar rats underwent standardized ulceration on the dorsum of the tongue using a punch of 5 mm diameter and were randomly allocated into the following groups: control (G1), chamomile fluid extract (G2), chamomile infusion (G3), aPDT (G4), and chamomile infusion + aPDT (G5). On the 3rd, 7th, and 14th days postoperatively, euthanasia was performed, and the ulcers were measured using calipers. The presence of edema, inflammatory infiltrate, cellularity, re-epithelialization, and characterization of total collagen were evaluated using sections stained with Hematoxylin and Eosin and Red Sirius. Histomorphometry analyses of the percentage of total collagen, the distance from the basal layer to the epithelial surface, and the thickness of the stratum corneum were performed. Descriptive (absolute/relative frequencies and modes) and exploratory analyses were performed. The associations between the groups and the presence of ulcers were analyzed with Fisher's exact test. All analyses were performed using the R program and statistical significance was set at p=0.05.

Results: The G2 positively modulated the exudative and proliferative phases of repair, both clinically (p<0.0001) and histologically, whether in descriptive or inferential analyses (p<0.05). The G3 showed a significant difference in clinical parameters compared with G1 (p<0.0001). The G4 and G5 did not positively modulate tissue repair.

Conclusion: The chamomile fluid extract showed better outcomes for tissue repair in the rat tongue.

Figure 1. Morphological analysis of experimental groups. Photomicrographs of histological sections stained with Hematoxylin and Eosin (HE) obtained in the 10× objective of the centers of the ulcers, demonstrating the degrees of re-epithelialization in the groups within 3, 7, and 14 days. Notably, the sections of all groups showed no re-epithelialization on the 3rd day. On the 7th day, only G2 exhibited complete re-epithelialization of all sections. The other groups exhibited initial epithelium formation at the wound edges, as shown in the G5 section (arrowhead). On day 14, although all groups showed complete epithelial coverage, G4 and G5 presented sections with no re-epithelialization. The G2, G4, and G5 also showed differentiation of lingual papillae (arrow). a: technique artifact. n: necrosis (LBO/UFBA, 2022)

Figure 2. Morphological analysis of experimental groups. Photomicrographs of histological sections stained with HE obtained in the 40× objective of the regions of the ulcers, illustrating the histomorphological characteristics in the groups within 3, 7, and 14 days. Notably, on the 3rd day, all groups exhibited edema (e) and inflammatory infiltrate (red asterisk). Ulcer area (arrowhead) can be observed in this period as well. At 7 days, G2 and G3 showed tissue cellularity – fibroblasts (black asterisk) and a collagen matrix (cm). On day 14, most groups showed no ulcer in all sections (G1, G2, and G3), with complete re-epithelialization. a: technique artifact. Black cross: blood vessel light (LBO/UFBO, 2022)

Figure 3. Morphological analysis of the experimental groups. Representative photomicrographs of histological sections (Red Sirius) to illustrate collagen expression on the 7th and 14th days obtained using a 10× objective. The groups showed a similar pattern from the 7th to the 14th day, in which fibers showed a normal appearance and a more delicate pattern (arrowhead), except for G2, which exhibited thicker but disorganized collagen fibers (asterisk). On day 14, the collagen fibers were thicker and organized in all groups. The G2 manifests a pattern close to normality. a: technique artifact.

Figure 4. Box plot of percentage of collagen area as a function of group and time