Association Between a Pro-Inflammatory Axis Comprised By TSP1-TGFβ-CTGF with Three microRNAs, Mir-19a, miR122 and Mir-133a in the Pathophysiology of Diabetic Retinopathy: A Therapeutic Novel Modality

Introduction: Diabetic retinopathy (DR) is a severe ocular complication of type 2 diabetes (T2DM). Our laboratory has been studying the role of a pro-inflammatory axis comprised by TSP1-TGFb and CTGF in T2DM. The axis is differentially expressed in patients with T2DM and non-proliferative DR (NPDR) when compared with patients with T2DM and proliferative DR (PDR). The differential expression of such axis is accompanied by interesting cytokine profiles as well. The purpose of this study was to evaluate potential microRNAs associated with the above changes in order to understand better the pathophysiology of T2DM. Recent studies indicate that miRNAs transported to exosomes or HDL can be transferred in an active form to recipients cells potentially involving them in cell-to-cell communication.

Methods: Institutional approved IRB and informed consent allowed this prospective study to recruit a total of 40 individuals afflicted by T2DM (n=20 NPDR and n=20 PDR) from the Ophthalmology Department Diabetes Clinic at Temple Hospital, normal controls (n=20) were recruited from the Sol Sherry Thrombosis Research Center at Temple. Western-blotting technique was utilized to document the presence of fragments from CTGF in plasma, which have been documented in vitreous fluid to be angiogenic. Multiplexed protein profiling on microarrays by rolling-circle amplification was employed to determine IL-4 and MIP-1b. Commercially available ELISA was the method to determine the plasma concentration of TSP1, TGFb and CTGF. Total RNA was extracted from human plasma using the miRCURY ^TM RNA isolation kit by Exiqon at their facility in Denmark.

Results and Discussion: TSP1, TGFb, CTGF, IL4, MIP-1b were significantly elevated in NPDR patients when compared to PDR patients. Fragments of CTGF were identified more abundant in patients with PDR when compared to NPDR. Only three microRNAs were differentially expressed in the normal group when compared with either NPDR (decreased), namely miR-133a (p<0.005), miR-19a (p<0.008), miR-122 (p<0.02) or PDR (decreased), miR-19a p<0.000096) and miR-122 (p<0.005). miR19a has been implicated with expression of TSP1 and CTGF, glucose levels, insulin resistance and diabetes-associated pancreatic cancer. miR-133a has been associated with cardiac hyperthrophy, fibrosis and heart failure in diabetes. miR-122 has been identified as a potential biomarker for non-alcoholic fatty liver. In summary our results link for the first time in the literature three circulating microRNAs with a the above axis in the pathophysiology of NPDR and PDR.