Microarray analysis of gene expression in fibrovascular membranes excised from patients with proliferative diabetic retinopathy

PURPOSE. We determined the profile of genes expressed in fibrovascular membranes (FVMs).

METHODS. Six FVMs were surgically removed from patients with proliferative diabetic retinopathy (PDR) during pars plana vitrectomy with membrane peeling. The FVMs were classified into three active FVMs or three inactive FVMs according to the presence or absence of neovascularization (NV) in the membranes. Total RNA was isolated from the six FVMs and also from three normal human retinas. The DNA microarray analysis was performed to compare the genes expressed in the FVMs to those in normal human retinas, and also between active and inactive FVMs. Ingenuity pathway analysis (IPA) was used to determine the key biological networks related to the genes that were significantly altered. Quantitative RT-PCR and immunohistochemistry were performed to validate the microarray analyses.

RESULTS. There were 87 genes expressed at significantly higher levels in FVMs than in normal human retinas. Functional classification of these genes showed that the most clustered genes were those related to extracellular matrix formation. The top biological network generated by the IPA was cellular assembly and organization involving nodes of genes related to extracellular matrix formation. These networks included the collagen family and matricellular proteins, THBS2, POSTN, and TNC. There were 91 genes significantly upregulated in active FVMs, and the most clustered functional category was angiogenesis. In contrast, 89 genes were significantly upregulated in inactive FVMs, and the most clustered functional category was metabolism. The IPA revealed that the top biological network related to the genes that were significantly altered in this comparison was cell-to-cell signaling, and interactions involving the PDGF and TGFβ families. The results of quantitative RT-PCR analyses and immunohistochemistry for several selected molecules were in good agreement with the microarray data.

CONCLUSIONS. Our data indicate that extracellular matrix-related molecules such as POSTN, TNC, TGFβ, and angiogenic factors have important roles in promoting the development of FVMs associated with PDR.