Effects of Cell-Free Fat Extract and Platelet-Rich Fibrin on Scar Maturation in an Experimental Rabbit Ear Wound Model

Abstract

Background: Multiple methods have been used to treat hypertrophic scarring; however, an optimal treatment method remains to be established. We aimed to research and compare the effects of cell-free fat extract (CEFFE) and platelet-rich fibrin (PRF) on hypertrophic scar formation based on histomorphological analysis in this study.

Methods: Twelve rabbits were divided into four groups randomly. (CEFFE+PRF group, n=3; CEFFE group, n=3, PRF group, n=3 and Control group, n=3). After the ear hypertrophic scar model were established, the two ears of each rabbit in the four groups were injected with CEFFE 0.05 mL/cm² + PRF 0.05 mL/cm², CEFFE 0.1 mL/cm², PRF 0.1 mL/cm², and saline 0.1 mL/cm², respectively. The scar elevation index and histological analysis using hematoxylin-eosin and Masson staining were evaluated after injection on day 40.

Results: The CEFFE+PRF group was significantly more effective in the prevention of pathological scar formation than the CEFFE-only, PRF-only, and control groups in terms of capillary count, collagen organization, fibroblast count, and scar elevation index (p<0.05).

Discussion: CEFFE combined with PRF was the most effective treatment for the prevention of hypertrophic scar formation in our study.

Keywords: effects of cell-free fat extract; hypertrophic scar; platelet-rich fibrin; rabbit.

Graphical abstract

Figure 1

Appearance of scars in each group 40 days after injection. (A) CEFFE+PRF Group, scale bar = 5mm. (B) CEFFE-only Group, scale bar = 5mm. (C) PRF-only Group, scale bar = 5mm. (D) Control Group, scale bar = 5mm.

Figure 2

Sample images by HE staining in the scar tissues. HE staining showed that the infiltration of inflammatory cells decreased after treatment, especially in the combination group, but almost no improvement in the control group. (A) CEFFE+PRF Group: regular collagen fibers (x100). scale bar = 100 μm. (B) CEFFE+PRF Group: (x400). scale bar = 20 μm. (C) CEFFE-only Group: (x100). scale bar = 100 μm. (D) CEFFE-only Group: (x400). scale bar = 20 μm. (E) PRF-only Group: (x100). scale bar = 100 μm. (F) PRF-only Group: (x400). scale bar = 20 μm. (G) Control Group: excessive deposition of the extracellular matrix and irregular collagen fibers. (x100). scale bar = 100 μm. (H) Control Group: Fibroblast cells and capillary formations, accompanied by a substantial infiltration of inflammatory cells. (x400). scale bar = 20 μm.

Figure 3

Sample images by Masson’s trichrome staining in the scar tissues. (A) CEFFE+PRF Group: the arrangement of collagen fibers in the combination group was the loosest and regular (x100). scale bar = 100 μm. (B) CEFFE+PRF Group (x400). scale bar = 20 μm. (C) CEFFE-only Group: (x100). scale bar = 100 μm. (D) CEFFE-only Group: (x400). scale bar = 20 μm. (E) PRF-only Group: (x100). scale bar = 100 μm. (F) PRF-only Group: (x400). scale bar = 20 μm. (G) Control Group: the collagen fibers were disordered and dense. (x100). scale bar = 100 μm. (H) Control Group: (x400). scale bar = 20 μm.

Figure 4

Summary of histopathological results. (A) Mean value of SEI score pre-injection and post-injection in each group. SEI index decreased after treatment, especially in the CEFFE+PRF group (SEI is defined as ratio of the vertical distance from the highest point of scar tissue to the ear cartilage surface and the vertical distance from the surrounding normal skin surface to the ear cartilage surface. (B) Mean value of epithelial thickness for each group in millimeters. (C) Mean number of fibroblasts in each group. (D) Mean number of capillary formations in each group. (E) Mean collagen organization score for each group. (ns, no significant difference. *p < 0.05.).