Regulation of microRNA to the expression of matrix metalloproteinases in bone marrow-derived cells in mice with choroidal neovascularization

Background Matrix metalloproteinases (MMPs) play important roles in the formation of choroidal neovascularization (CNV), but its mail origin is not ocular cells in situ.Bone marrow-derived cells (BMCs) participate in the formation of CNV and is probably a primary source of expressing MMPs in CNV.MMP-2/MMP-13 is speculated to be the regulating target genes of miR188-5p. Objective This study was to verify whether BMCs are the main source of MMPs, and whether the MMP-2/MMP-13 expression is potentially regulated by miR188-5p. Methods BMCs expressed green fluorescent protein (GFP) from transgenic female C57BL/6J mice were transplanted to female wild-type C57BL/6J mice to establish C57BL/6J. GFP chimeras models, and 42 mice with chimerisms more than 85% by flow cytometry were included as the experimental group.Other 42 wild-type C57BL/6J mice without the BMCs transplantation were enrolled as the control group.CNV was induced by laser coagulation of retinas on the mice of both groups.MMP-2/MMP-13 levels in the retinochoroid tissue were quantified by ELISA at day 1, 3, 5, 7, 10, 14, and 28 after photocoagulation.The expression of miR188-5p mRNA in the retinochoroid tissue was assayed by real-time quantitative PCR (RT-qPCR).Immunofluorescence stain and fluorescent in situ hybridization were used to identify the MMP-2/MMP-13 and miR188-5p expressed by GFP-positive BMCs in CNV, and the expression level was quantified by images analysis. Results The proportion of GFP+mouse mononuclear cells was (90.67±3.02)% in the C57BL/6J.GFP chimeras.The concentration changes of MMP-2/MMP-13 in retinochoroid homogenate showed a same tendency with the lapse of time between the experimental group and the control group (MMP-2:F=0.060, P=0.810;MMP-13:F=0.012, P=0.915).The expression level was zoomed in retinochoroid tissue after induce of CNV with the maximal value on the third day in both groups, and the proportion in the experimental group was 64.21%;while the expression level of MMP-13 was slowly raised after induce of CNV with the peak at the seventh day, and the proportion in the experimental group was 79.61%.A complementary association point of miR188-5p was exhibited in the 3'-untranslated regions of MMP-2 or MMP-13 by target gene prediction.The expression level of miR188-5p mRNA in the BMCs of CNV area was sharply declined after induce of CNV with the lowest value on the seventh day.A negative correlation was found between the expressing level of miR188-5p and MMP-13 protein (r=-0.868, P<0.05) as well as early stage of expression level of MMP-2 protein (r=-0.997, P<0.05). Conclusions The elevation of MMP-2/MMP-13 expression levels is associated with the formation of CNV, and the regulation of miR188-5p expression in the BMCs of CNV area is responsible for increase of MMP-2/MMP-13 expression. The tendency of miR188-5p expression is inversed with MMP-2/MMP-13. Key words: Choroidal neovascularization; Matrix metalloproteinase; Bone marrow cell; MicroRNA