Functional Assessment of Fibroblast Heterogeneity by the Cell-Surface Glycoprotein Thy-1

Abstract

Fibroblasts are a heterogeneous population of structural cells whose primary function is the production of extracellular matrix for normal tissue maintenance and repair. However, fibroblasts provide much more than structural support as they synthesize and respond to many different cytokines and lipid mediators and are intimately involved in the processes of inflammation. It is now appreciated that fibroblasts exhibit phenotypic heterogeneity, differing not only between organ systems, but also within a given anatomical site. Subtypes of fibroblasts can be identified by the expression of markers such as Thy-1, a cell surface glycoprotein of unknown function. Initial characterization of fibroblasts as Thy-1+ or Thy-1− can be performed by immunofluorescence or flow cytometry. They can be sorted according to their expression of Thy-1 by fluorescence-activated cell sorting (FACS), cloning and/or magnetic beading, yielding greater than 99% purity. Fibroblasts that are separated into Thy-1+ and Thy-1− subsets exhibit differences in their morphological, immunological and proliferative responses and ability to differentiate into a-smooth muscle actin-expressing myofibroblasts and adipocyte-like lipofibroblasts, key cells for wound healing and fibrotic disorders. The identification of Thy-1 as a surface marker by which to separate fibroblast subtypes has yielded vital insight into diseases such as scarring and wound healing and highlights the concept of fibroblast heterogeneity. Future research into fibroblast subsets may lead to the tissue-specific treatment of disease such as idiopathic pulmonary fibrosis and Graves’ ophthalmopathy.