Effects of Pirfenidone and Collagen-Polyvinylpyrrolidone on Macroscopic and Microscopic Changes, TGF- β 1 Expression, and Collagen Deposition in an Experimental Model of Tracheal Wound Healing

Abstract

Tracheal stenosis (TS) is a fibrosis originated by prolonged inflammation and increased transforming growth factor beta 1 (TGF-β1) expression and collagen deposition (CD) in the tracheal wound. Several wound-healing modulators (WHMs) have been used to modulate the tracheal healing process and prevent TS, but they have failed, justifying the need to evaluate alternative WHM. The pirfenidone (PFD) and collagen-polyvinylpyrrolidone (Collagen-PVP) decrease inflammation and fibrosis. This study assessed the effect of PFD administration and Collagen-PVP topical application on macroscopic and microscopic changes, TGF-β1 expression, and CD in an experimental model of tracheal wound healing. Forty Wistar rats underwent cervical tracheoplasty, were divided into 4 groups (n = 10), and were treated with different WHM: group I, saline solution (SS); group II, Collagen-PVP; group III, mitomycin C (MMC); and group IV, 40 mg/kg PFD. Four weeks after surgery, the macroscopic and microscopic changes, in situ TGF-β1 expression, and CD in posttracheoplasty scars were evaluated. The animals treated with Collagen-PVP and PFD developed less inflammation and fibrosis than animals in the other study groups (p < 0.05, Kruskal-Wallis) and, moreover, showed lower TGF-β1 expression and CD than animals in group I (p < 0.05, ANOVA and Tukey's test). In conclusion, PFD and Collagen-PVP decrease inflammation, fibrosis, TGFβ-1 expression, and CD in the posttracheoplasty rats' scar.

Figures

Figure 1

Tracheal wound healing and lumen diameter at the end of the study. (a) Normal wound healing and minimal tracheal lumen decrease in an animal from the SS group. Normal wound healing without stenosis in the group treated with Collagen-PVP (b) and PFD (d). (c) Fibrotic scarring and decreased tracheal lumen in a euthanized animal from group III.

Figure 2

Micrograph of tracheal wound healing stained with Masson's trichrome (40x magnification). (a) Moderate inflammation and moderate amount of disorganized, thick collagen fibers in group I. (b) Mild inflammation and minimal number of organized, thick collagen fibers in the Collagen-PVP group. (c) Moderate inflammation and fibrosis with a moderate amount of disorganized, thin collagen fibers in animals from group III. (d) Tracheal wound free of inflammation and few organized, thin collagen fibers in the group treated with PFD.

Figure 3

Photomicrographs of immunohistochemical detection of TGF-β1 in tracheal scar (40x), showing strong TGF-β1 expression (dark brown immunostaining) in the SS (a) and MMC (c) groups, in contrast to weak TGF-β1 expression (light brown immunostaining) in animals treated with Collagen-PVP (b) and PFD (d).

Figure 4

Amount of collagen formed per mg of tracheal tissue in each group, 28 days after tracheal surgery, and a comparison among groups. Each bar represents the mean ± EE of the collagen concentration in the tracheal tissue for each study group; ∗p < 0.05 (ANOVA and Tukey's test) showing the reduced collagen depositions observed in the PFD group versus the SS group. X-±SE. ∗p < 0.05 ANOVA, Tukey's test, PFD versus SS.