Comprehensive Proteomic Profiling of Aqueous Humor Proteins in Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is a serious ocular disease that can lead to retinal microvascular complications in patients with diabetes mellitus. To date, no studies have explored PDR development by analyzing the aqueous humor (AH). Therefore we carried out tandem mass tag (TMT) proteomic quantification to compare AH protein profiles between PDR and non-PDR subjects.

We enrolled six PDR and six control (senile cataract) subjects. AH samples were collected during surgery and stored at -80°C. Proteins were extracted, trypsin-digested, and labeled with TMTs for mass spectrometric analysis.

We found 191 proteins to be changed with |log2 (fold change)| ≥1 (P < 0.05 and identification with at least two peptides per protein). Of them, 111 were downregulated, whereas 80 were upregulated in the PDR group. Proteomic bioinformatic analysis indicated that PDR development was related to complement and coagulation cascades, platelet activation, extracellular matrix-receptor interaction, focal adhesion, protein digestion and absorption, human papillomavirus infection, PI3K-Akt signaling pathway, cholesterol metabolism, peroxisome proliferator-activated receptor signaling pathways, fat digestion and absorption, and vitamin digestion and absorption pathways.

Comprehensive proteomic profiling of the AH revealed 191 differentially expressed proteins between the two groups. Most of these proteins belong to secretory pathways, and therefore can be used as biomarkers in clinical testing and basic research.

Pathway analysis and a review of the literature enabled us to draw a novel biological map that will support further studies on the underlying mechanisms and therapeutic control of PDR development.