Abstract
Purpose: :
CD9, a member of the tetraspanin protein family, is involved in important cellular processes like proliferation, migration and differentiation. It is expressed in a wide variety of cells including several cell types present in retina and choroid. Here we describe the investigation of its expression and putative function in pigment epithelial cells using the well-established ARPE-19 cell line.
Methods: :
Expression of CD9 in ARPE-19 was analyzed by immunofluorescence staining. Proliferation of ARPE-19 cells and its modulation by a CD9-specific antibody was studied by a standard WST-1 proliferation assay (Roche) and in a wound healing assay, in which cell migration was also monitored. In the wound healing assay, the cell monolayer was disrupted with a cell scraper (1.6 mm) and repair of the lesion in the presence and absence of anti-CD9-antibody or control antibody was measured after 24hours and 48hours. In addition, lesion closure was recorded by videomicroscopy.
Results: :
CD9 is localized mainly in the plasma membrane in confluent ARPE-19 with additional intracellular staining as shown by immunofluorescence staining. A CD9-specific monoclonal antibody significantly inhibited proliferation of ARPE-19 and lesion repair in a wound-healing assay (endpoint after 48 hours). Analysis of videomicroscopic images strongly suggested that both migration and proliferation of ARPE-19 was affected.
Conclusions: :
We previously described that tetraspanins CD9, CD63, CD151 are expressed in the retina and the choroid. Our results indicate that CD9 also plays a role in the regulation of proliferation and migration of pigment epithelial cells. Since cellular processes that are deregulated in retinal diseases like diabetic retinopathy are the same for which a functional involvement of tetraspanins is known, a contribution of such proteins to pathogenic processes in the eye can be assumed.
Keywords: retinal pigment epithelium • wound healing • microscopy: light/fluorescence/immunohistochemistry