Metabolic variations in normal and fibrotic human laryngotracheal‐derived fibroblasts: A Warburg‐like effect

Abstract

Objective/Purpose Laryngotracheal stenosis (LTS) is a chronic fibrotic disease characterized by fibroblast proliferation, collagen deposition, and matrix remodeling in the lamina propria of the larynx and/or trachea. Current medical therapies are limited by a poor understanding of the effector cell’s (fibroblasts) cellular biology and metabolism. The purpose of this study is to compare cellular proliferation, function, and metabolism between normal and LTS-derived fibroblasts in vitro. Methods Human biopsies of normal and iatrogenic LTS tissue (n=7) were obtained and fibroblasts were isolated and cultured in vitro. Cellular proliferation, cellular histology, gene expression and metabolic analyses were performed. Statistical analyses comparing normal and scar-derived fibroblasts were performed. Results LTS fibroblast proliferation rate, cellular surface area, and collagen-1 expression were increased compared to normal fibroblasts. Cellular metabolic analysis of LTS-derived fibroblasts demonstrated reduced oxidative phosphorylation and increased glycolysis/oxidative phosphorylation ratio compared with normal fibroblasts. Conclusion Human iatrogenic LTS-derived fibroblasts demonstrated aberrant behavior when compared with normal fibroblasts. A Warburg-like effect was revealed suggesting human iatrogenic LTS fibroblasts drive their proliferation with aerobic glycolysis. The distinct metabolism suggests metabolic inhibitors could reduce fibroblast hyperplasia and hypertrophy in LTS and fibrosis in general.

Fibroblasts in Hypoxic Conditions Mimic Laryngotracheal Stenosis

“…8 Recent studies have shown that compared to normal fibroblasts, fibroblasts isolated from laryngotracheal scar proliferate faster, exhibit metabolic changes, and express more collagen. 9 This echoes the fibrotic phenotype observed in other organs. In cardiac fibrosis, fibroblasts transdifferentiate into myofibroblasts in response to ischemic injury, producing excessive ECM and a contracted scar.…”

“…31 This allows fibroblasts to shift its energy production from an oxygen-dependent pathway to an oxygen-independent pathway, creating the Warburg-like effect that we’ve previously described in our scar fibroblasts. 9 …”

Targeting metabolic abnormalities to reverse fibrosis in iatrogenic laryngotracheal stenosis

“…All biopsies were obtained by the same surgeon, with source tissue initially identified by visual inspection. Primary fibroblasts were isolated from the biopsy specimens, cultured, and expanded—and then experiments were performed with passage 2 or 3 cells, as in earlier work . Cellular phenotype was confirmed through immunohistochemical staining, as previously described …”

“…However, the underlying differences in these fibroblasts are poorly understood, including biologic and metabolic differences between scar and normal laryngotracheal fibroblasts. Recent evidence indicates that there are distinct abnormalities in iLTS scar fibroblasts when compared to normal airway fibroblasts from the same patient . iLTS scar fibroblasts are hyperproliferative, have increased extracellular matrix (ECM) deposition, and demonstrate a metabolic shift to reduced oxidative phosphorylation and increased aerobic glycosis .…”

“…Recent evidence indicates that there are distinct abnormalities in iLTS scar fibroblasts when compared to normal airway fibroblasts from the same patient . iLTS scar fibroblasts are hyperproliferative, have increased extracellular matrix (ECM) deposition, and demonstrate a metabolic shift to reduced oxidative phosphorylation and increased aerobic glycosis . A similar phenotype wherein hyperproliferation is driven by aerobic glycolysis is seen in fibrosis of other organs, as in the case of idiopathic pulmonary fibrosis (IPF) .…”