In diabetic retinopathy patients the expression of circ_0005015 was elevated in the fibrovascular membranes, the plasma and the vitreous sample, which resulted in enhanced endothelial angiogenic responses via sponging miR-519d-3p and increased expression of matrix metallopeptidase 2 (MMP-2), signal transducer and activator of transcription 3 (STAT3), and X-linked inhibitor of apoptosis (XIAP) (Zhang et al., 2017). Here, MMP2 is linked to diabetic retinopathy.