Introduction  Anterior and tangential traction on the macular area is believed to cause the idiopathic macular hole formation. The contraction of the ERM contributes to the subsequent hole enlargement and surgical failure. It has been reported that many extracellular matrix proteins and cells are involved in the ERM formation. Little is known about the distribution of the ECM and the relationship with the cellular components in the epiretinal membrane of macular hole. With the advantages of flat mount technique, we report the ECM components, which are involved in epiretinal membrane formation of macular hole. These findings will provide a better understanding of the pathogenesis of idiopathic macular hole formation at the cellular and molecular level.
Purpose  To evaluate the presence and distribution of extracellular matrix (ECM) proteins and cellular components associated with the inner limiting membranes (ILMs) of idiopathic macular hole.
Methods  ILMs were obtained from patients who underwent vitrectomy combined with ILM peeling for idiopathic macular hole. These samples were flat-mounted and subjected to immunohistochemistry. The distribution of type I, III, IV, V and VI collagen, CD68 (a macrophage marker) and Glial Fibrillary Acidic Protein (GFAP, glial cell marker) were mapped. Images were documented by fluorescent microscope and confocal laser scanning microscope (CLSM).
Results  Thirteen out of 23 cases showed a fibrocellular complexes on the clinical examination. All of them showed fibrocellular proliferation microscopically. The ERM were positive for collagen type I, III and V, CD68 and GFAP. Type II and VI collagen were not observed on these fibrocellular membranes. GFAP-positive gliosis was found on the surface of all ILMs that at individually variable distances to the edge of the macular hole.
Discussion  The initial macular hole formation may induce a wound healing process as well as an inflammatory reaction. The fibrocellular membrane formed on the ILM contains newly produced collagen types I, III, and V. The fibrillar collagens are the critical elements for contractile cells to exert traction, and may influence the rigidity of the membrane as well as the adhesion between the membrane and the underlying tissue. For surgeons, it is important since these properties may have impacts on ILM peeling.