Effects of corticosteroids vs halofuginone on vocal fold wound healing in an ovine model

Abstract

Objectives To evaluate antifibrotic effects of corticosteroids and halofuginone, a small molecule inhibitor of Smad3, in an ovine model of vocal fold (VF) injury. Methods Thirty sheep, using a paired study design, underwent controlled right VF injury by biopsy and then were treated with either no treatment, oral dexamethasone, intralesional triamcinolone, or oral halofuginone. Larynges were evaluated for histological evidence of fibrosis, immunohistochemical presence of Smad3, and vibratory parameters. Outcomes were compared across treatment groups. Results Following injury, VF collagen density decreased in both halofuginone‐treated and dexamethasone‐treated sheep but not in triamcinolone treated sheep. A significant difference was noted between halofuginone and triamcinolone treated sheep (27.8% vs 37%, P = .017). Elastin was preserved postinjury by halofuginone treatment in contrast with all steroid treated animals where significant loss of elastin was noted (P <.05). Smad3 staining was up‐regulated at all injury sites compared to normal left VFs however halofuginone and dexamethasone treatment reduced Smad3 activity significantly whereas triamcinolone treatment did not (P <.05). Ex‐vivo stroboscopic evaluation demonstrated mucosal wave in all excised larynges with a normalized glottal gap less than 3, suggesting adequate glottal closure. Conclusions VF injury in an ovine model results in a wound response able to be modified by Smad3 inhibitor, halofuginone, with benefit to vibratory function. Halofuginone treated sheep demonstrated reduced collagenization of lamina propria with greater elastin density after injury, than sheep treated with either steroid medication. These data support this pathway as a suitable target for manipulation to prevent or reverse fibrosis in the glottis and restore voice quality. Level of Evidence: NA.

Effects of compound betamethasone on vocal fold wound healing in rabbit model: A preliminary study

“…In this study, VF injuries resulted in the decreased HA and the elevated collagen no matter what was injected into the VFs, compared to the control group. This was consistent with the previous study 22. Kishimoto et al found that the scar-associated collagen accumulation might be reversed within 4 weeks by the knockdown of a collagen-specific siRNA 23.…”

“…This was consistent with the previous study. 22 Kishimoto et al found that the scar‐associated collagen accumulation might be reversed within 4 weeks by the knockdown of a collagen‐specific siRNA. 23 …”

Current approaches to management of vocal fold scar

“…Wound healing in the VF follows known phases of haemostasis and formation of a platelet plug, vasoconstriction, release of cytokines and mediators that stimulate influx of repair cells and produce an inflammatory response, proliferation of cells and substrates and then remodelling and restitution. Cellular machinery involved in this process is akin to elsewhere in the body, however, VF fibroblasts (VFF), key participants in this process, can drive a pro-fibrotic state that results in imbalance of reticular elements (increase in collagen and loss of elastin) in addition to changes in the extracellular matrix (ECM) constitution [1,4,5]. Collagen typically accounts for 43% by weight of total protein in the SLP and is most dense in the deep layer of the fold [6].…”

“…IL-17 is implicated in a wide range of autoimmune diseases, is strongly inflammatory, and was recently identified as promoting subglottic stenosis through activation of fibroblasts cultured from SGS tissue [16,17]. Abrogation of IL-17 effects may be a pathway worthy of further exploration to halt airway stenosis, and halofuginone, a known inhibitor of T H17 cell differentiation has demonstrated antifibrotic effects, potentially acting through this mechanism in combination with its known Smad inhibition effects [1,18].…”

“…TGF-ß effects are mediated through the Smad family of intracellular messengers which are activated by ligand binding at TGF-receptors. In the cytosol, Smad2, 3 and 4 form a trimeric molecule that may translocate to the nucleus and bind directly to DNA promotor elements to trigger collagen type 1A transcription [1]. Inhibition of Smad3 has become a target for modifying the fibrotic response, with Allen reporting Smad antagonism using halofuginone, and Branski et al developing and utilizing small interfering (silencing) RNA [siRNA] vs Smad3 [1,19,20].…”