Macrophages promote a profibrotic phenotype in orbital fibroblasts through increased hyaluronic acid production and cell contractility

Abstract

Graves’ orbitopathy (GO) is an autoimmune inflammatory disease affecting the orbit. Orbital fibroblasts are a key component in GO pathogenesis, which includes inflammation, adipogenesis, hyaluronic acid (HA) secretion, and fibrosis. Macrophages are thought to participate in the immunological stage of GO, but whether they can directly affect the fibroblasts phenotype and modulate disease progression is unknown. We previously showed that GO adipogenic and fibrotic phenotypes could be modelled in a pseudo-physiological 3D environment in vitro . Here, we introduced macrophages in this 3D culture model to investigate role for macrophages in modulating adipogenesis, HA production, and contractility in orbital fibroblasts. Macrophages had a minimal effect on lipid droplet formation in fibroblasts, but significantly increased HA production and cell contractility, suggesting that they may promote the fibrotic phenotype. This effect was found to be mediated at least in part through phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) activation and linked to an increase in actin polymerization and protrusive activity in fibroblasts. Overall our work shows for the first time a direct role for macrophages in modulating the fibroblasts’ phenotype in GO, supporting a role for macrophages in the progression of the fibrotic phenotype through induction of HA production and stimulation of the contractile phenotype in orbital fibroblasts.

Fibrosis in dysthyroid eye disease

“…The macrophages also promoted a contractile phenotype in the OF but no increase in expression of α-SMA. All these effects were more marked in TED than healthy control OF and mediated in part by PI3kinase (35).…”

MicroRNA-146a downregulates the production of hyaluronic acid and collagen I in Graves' ophthalmopathy orbital fibroblasts

“…GO is a common eyelid disorder that seriously affects the appearance and visual function of patients, while severe GO may also result in blindness (23). GO has been indicated to be initiated with an autoimmune inflammatory response, HA synthesis and collagen deposition, resulting in connective tissue hyperplasia and fibrosis (24). Orbital fibroblasts have been revealed to be an important pathogenetic factor of GO, contributing to inflammation, lipogenesis, HA secretion and fibrosis in GO (24).…”

“…GO has been indicated to be initiated with an autoimmune inflammatory response, HA synthesis and collagen deposition, resulting in connective tissue hyperplasia and fibrosis (24). Orbital fibroblasts have been revealed to be an important pathogenetic factor of GO, contributing to inflammation, lipogenesis, HA secretion and fibrosis in GO (24). HA is the principal component of GAG aggregation and exhibits high hydrophilicity binding to a large amount of water, thereby resulting in an abnormal eyelid tissue and extraocular muscle interstitial edema (25).…”

Isolation and Characterization of Extraocular Muscle-Derived Muscle Progenitor Cells from Normal and Graves' Orbitopathy Patients

“…A previous study reported that a COX-2 inhibitor significantly inhibited HAS3-induced HA production through a TGF-brelated pathway after TNF-a stimulation in GO myoblasts [6]. In addition, co-cultured macrophages can induce HA synthesis in orbital fibroblasts from GO patients, independent of IGF-1R signaling [44]. The activated orbital fibroblasts then secrete cytokines such as IL-1b to upregulate the production of prostaglandin E2.…”