Exploring the Immune Infiltration Landscape and M2 Macrophage-Related Biomarkers of Proliferative Diabetic Retinopathy

Abstract

BackgroundsDiabetic retinopathy (DR), especially proliferative diabetic retinopathy (PDR), is the major cause of irreversible blindness in the working-age population. Increasing evidence indicates that immune cells and the inflammatory microenvironment play an important role during PDR development. Herein, we aim to explore the immune landscape of PDR and then identify potential biomarkers correlated with specific infiltrating immune cells.MethodsWe mined and re-analyzed PDR-related datasets from the Gene Expression Omnibus (GEO) database. Using the cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT) algorithm, we investigated the infiltration of 22 types of immune cells in all selected samples; analyses of differences and correlations between infiltrating cells were used to reveal the immune landscape of PDR. Thereafter, weighted gene co-expression network analysis (WGCNA) and differential expression analysis were applied to identify the hub genes on M2 macrophages that may affect PDR progression.ResultsSignificant differences were found between infiltration levels of immune cells in fibrovascular membranes (FVMs) from PDR and normal retinas. The percentages of follicular helper T cells, M1 macrophages, and M2 macrophages were increased significantly in FVMs. Integrative analysis combining the differential expression and co-expression revealed the M2 macrophage-related hub genes in PDR. Among these, COL5A2, CALD1, COL6A3, CORO1C, and CALU showed increased expression in FVM and may be potential biomarkers for PDR.ConclusionsOur findings provide novel insights into the immune mechanisms involved in PDR. COL5A2, CALD1, COL6A3, CORO1C, and CALU are M2 macrophage-related biomarkers, further study of these genes could inform novel ideas and basis for the understanding of disease progression and targeted treatment of PDR.

Identification of differential immune cells and related diagnostic genes in patients with diabetic retinopathy

“…Many studies have shown that M2 macrophages may participate in proliferative diabetic retinopathy (PDR) angiogenesis. [23][24][25] The microglia or macrophages were activated in an oxygen-induced retinopathy model. Inhibiting macrophage polarization to M2 phenotype can inhibit the generation of retinal neovascularization, which may be an effective way to treat retinal neovascular diseases.…”

Inflammation in diabetes complications: molecular mechanisms and therapeutic interventions

“…24 At early stage of DR, both M1 and M2 microglia/macrophages were activated, but the numbers of M2 macrophages decreased with disease progress, and eventually resulted in retinal dysfunction. Previous data showed M2 macrophages-related genes, such as COL5A2 and CALD1, were highly expressed in immune cells in the retinal fibrovascular membrane and could be used as potential biomarkers for proliferative DR. 14 It has been reported that asiatic acid reduced M1 polarization through TLR4/MyD88/NF-κB p65 pathway and increased M2 polarization to prevent early DR. 25 Histone demethylase Kdm6a could affect the gene transcription of macrophages, thereby affecting retinal thickness, visual acuity, and aggravating the development of DR. 26 Macrophages can affect the neurovascular function of peripheral nerve tissue and regulate the occurrence of neuroinflammation. By analyzing the sciatic nerve of DPN mice, it was found that the markers of M1 macrophages such as TNF-α and IL-1β increased, and the markers of M2 macrophages such as IL-10 and TGF-β decreased, 27 while after treatment, macrophages expressed lower levels of proinflammatory genes and higher levels of anti-inflammatory genes.…”

“…At early stage of DR, both M1 and M2 microglia/macrophages were activated, but the numbers of M2 macrophages decreased with disease progress, and eventually resulted in retinal dysfunction. Previous data showed M2 macrophages‐related genes, such as COL5A2 and CALD1 , were highly expressed in immune cells in the retinal fibrovascular membrane and could be used as potential biomarkers for proliferative DR 14 . It has been reported that asiatic acid reduced M1 polarization through TLR4/MyD88/NF‐κB p65 pathway and increased M2 polarization to prevent early DR 25 .…”

“…In addition, inflammation was used as a biomarker to predict the occurrences of diabetes complications including DCM, 6 DN, 7 DR, 8 and DPN 9 . Inflammatory cytokines such as tumor necrosis factor‐α (TNF‐α), 8 transforming growth factor‐β (TGF‐β), 10 interleukins (ILs), 11 adhesion molecules, 12,13 and other genes related to macrophage could be used as biomarkers 14 . Due to the complex roles of inflammation in the occurrence and development of diabetes complications, their relationship has not been fully clarified.…”

Role of macrophage in ocular neovascularization

“…Furthermore, macrophages are involved in the proliferative membranes of PDR patients with or without vitreous hemorrhage [ 43 ]. The number of macrophages increases in fibrovascular membranes, vitreous samples, and iris of PDR patients compared with nondiabetic controls [ [44] , [45] , [46] , [47] ]. In the iris, macrophage staining is more pronounced in diabetics than in non-diabetics.…”