Abstract
Purpose: :
Diabetic retinopathy (DR) is one of the leading causes of blindness in the industrialized world. However, there is still no efficient treatment. And the processes of development and testing new drugs have been hampered by the lack of biomarkers for accurate diagnosis and evaluation of the pathological progression of the disease. microRNAs (miRNAs) are newly-recognized level of gene-expression regulation, and have emerged as novel biomarkers for various diseases. However, whether miRNAs are expressed in the vitreous as as potential biomarkers for the diagnosis of DR has not been studied at all. The purpose of this research is to answer this question.
Methods: :
We induced diabetes in Sprague-Dawley rats by STZ injection. 2 weeks after STZ-induced diabetes, we prepared total RNA from vitreous of 3 diabetic and 3 normal control rats. We performed miRNA expression profiling using the TaqMan rodent miRNA microarray_v2.0 (Applied Biosystems). By comparison of the miRNA expression profiles, we identified miRNAs differentially expression in the vitreous of STZ-induced diabetic rats compare to normal controls.
Results: :
1. The yield of total RNA is ~764 ng and 1125 ng RNA/vitreous of control and diabetic rats, respectively.2. miRNAs are expressed the vitreous with a stable and consistent expression pattern. Approximately 236 and 279 miRNAs are detected in the vitreous of normal control and STZ-induced diabetic rats.3. At least 21 miRNAs are significantly upregulated and 8 miRNAs significantly downregulated (p<0.05) in the vitreous of diabetic rats compared to normal control, suggesting that these miRNAs may reflect pathological changes in the retina and eyes of diabetic animals at this early stage of DR.4. Further analysis on the differentially expressed miRNAs revealed that a. Co-expressed miRNAs tend to change their levels of expression simultaneously; b. Endothelial specific miRNAs are increased by in the vitreous of diabetic animals, possible a result of increased REC damage in early DR. c. neuroretinal specific miRNAs are significantly upregulated in the vitreous of diabetic rats, possibly reflecting increased damage of retinal neurons in early DR.
Conclusions: :
1. miRNAs exist in the vitreous with a unique and stable expression pattern; 2. specific changes in miRNA expression in the vitreous of diabetic rats occur as early as two weeks after the onset of diabetes; miRNA signatures in the vitreous may represent early pathological changes in both retinal microvasculature and retinal neurons, strongly supporting that miRNA signatures may be potential biomarkers for the diagnosis of DR.
Keywords: diabetic retinopathy • vitreous • gene microarray