Extraocular Muscle Derived Fibroblasts Differ From Fibroblasts of Other Skeletal Muscle

Abstract

Purpose:: Fibroblasts secrete an extracellular matrix which provides an ideal environment for the growth of other cell types, such as embryonic stem cells, keratinocytes, and neuronal progenitors. However, accumulation of extracellular matrix also can be detrimental in diseases such as Graves’ ophthalmopathy. A closer look at the functions of fibroblasts in Grave’s ophthalmopathy has brought focus on the obital fibroblast, as well as, perimysial fibroblasts of the EOM. Perimysial fibroblasts from extraocular muscle (EOM) may play a role in the progression of Grave’s ophthalmopathy through the accumulation of glycosaminoglycans by IL-1 and TGF-ß stimulation. However, focus has also been extended to the extraocular muscle as the target of autoantibody binding. Perimysial fibroblasts differ from those of the orbital fibroblast and therefore, may behave differently when exposed to cytokines and growth factors.

Methods:: Perimysial fibroblast from the leg (LM-Fibro) and EOM (EOM-Fibro) of C57BL/6J mice (3-5 week old) were individually derived and maintained in culture. Fibroblast cultures were assessed by the morphology, and immunohistochemistry with antibodies to vimentin and smooth muscle actin. Thy-1 expression was determined by Flow cytometric analysis and immunohistochemistry. Microarray analysis was performed on LM-Fibro and EOM-Fibro grown in cultured conditions of 2% horse serum and serum free.

Results:: EOM- and LM-Fibro proliferate as a monolayer. EOM-Fibro morphology is flat with few extensions while LM-Fibro exhibit angular shapes with multiple dendritic processes. Both LM-Fibro and EOM-Fibro expressed vimentin. A few cell showed expression of smooth muscle actin. Thy-1 expression pattern in EOM-Fibro is 39% positive compared to 30% in LM-Fibro. Microarray demonstrated several differences between the cultures largely in the transcription family of genes.

Conclusions:: EOM-Fibro demonstrates differences from fibroblasts of other skeletal muscle. The distinct properties of EOM-Fibro may help to explain unique recognition and responses to inflammatory disorders and treatments.

Keywords: extracellular matrix • extraocular muscles: structure