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Warren Campbell, Ameya deshmukh, Sydney Blum, Jennifer Leight, Andrew J Fischer; Gelatinase activity and the formation of Müller glia-derived progenitor cells in the avian retina. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2339.
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Matrix metalloproteinase 2 and 9 (MMP-2, MMP-9) and the tissue inhibitors of matrix metalloproteinases (TIMPs) are important regulators of the extracellular matrix (ECM) and have been implicated in retinal function, development, and pathology. We hypothesized that gelatinase activity decreases in response to retinal damage and influences the reprogramming of Müller glia into proliferating progenitor cells. Thus, the purpose of this study was to investigate changes in gelatinase activity and how this activity influences the formation of Müller glia derived progenitor cells (MGPCs) in the chick model system.
Chicks (white leghorn strain) aged P7-P21 were subject to intravitreal injection of NMDA (74µg/dose) and harvested at 4, 24, 48, 72, and 7 days after damage. Gelatinase activity was measured by embedding tissue into a hydrogel containing a bicysteine MMP-degradable peptide (10.75 mM, KCGPQG↓IWGQCK) using fluorescent resonance energy transfer (FRET). MMP activity was suppressed by small molecule inhibitors SB-3CT and MMP2i-II that were delivered intravitreally. MMP and TIMP expression was assessed by using single cell RNA sequencing (10X Genomics). Significance of difference was assessed via a Student’s T test, one-way ANOVA, and Tukey’s test for multiple comparisons.
MMP-2 was expressed by oligodendrocytes and non-astrocytic inner retinal glia (NIRGs). Gelatinase activity was significantly decreased 24 hrs (ctrl 0.975 ± 0.081, trt 0.684 ± 0.184; n = 4; p < 0.01), 48 hrs (ctrl 0.989 ± 0.047, trt 0.377 ± 0.085; n = 4; p < 0.0001), 72 (ctrl 0.821 ± 0.156, trt 0.457 ± 0.013; n = 4; p < 0.05), and 168 hrs (ctrl 0.679 ± 0.070, trt 0.538 ± 0.142; n = 4; p < 0.05) after NMDA damage. This decrease in activity correlated with an increase in TIMP2 expression in Müller glia and TIMP3 expression in NIRG cells. Treatment with SB-3CT or MMP2i-II increased the formation of proliferating MGPCs in damaged retinas (SB-3CT - ctrl 18 ± 8, trt 57 ± 22; n = 8; p < 0.01; MMP2i-II - ctrl 48 ± 21, 84 ± 20; n = 8; p < 0.05).
In response to damage, gelatinase activity is significantly reduced for several days, which correlates with an increase in expression of TIMP2 in Müller glia and TIMP3 in NIRGs. Treatment with gelatinase inhibitors potentiates MGPC formation in damaged retinas. Thus, inhibition of gelatinases may represent a therapeutic target to facilitate retinal regeneration.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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