IGF-1R Regulates the Extracellular Level of Active MMP-2, Pathological Neovascularization, and Functionality in Retinas of OIR Mouse Model

Abstract

In ischemic proliferative diseases such as retinopathies, persistent hypoxia leads to the release of numerous neovascular factors that participate in the formation of abnormal vessels and eventually cause blindness. The upregulation and activation of metalloproteinases (MMP-2 and MMP-9) represent a final common pathway in this process. Although many regulators of the neovascular process have been identified, the complete role of the insulin-like growth factor 1 (IGF-1) and its receptor (IGF-1R) appears to be significantly more complex. In this study, we used an oxygen-induced retinopathy (OIR) mouse model as well as an in vitro model of hypoxia to study the role of MMP-2 derived from Müller glial cells (MGCs) and its relation with the IGF-1/IGF-1R system. We demonstrated that MMP-2 protein expression increased in P17 OIR mice, which coincided with the active phase of the neovascular process. Also, glutamine synthetase (GS)-positive cells were also positive for MMP-2, whereas IGF-1R was expressed by GFAP-positive cells, indicating that both proteins were expressed in MGCs. In addition, in the OIR model a single intravitreal injection of the IGF-1R blocking antibody (αIR3) administered at P12 effectively prevented pathologic neovascularization, accelerated physiological revascularization, and improved retinal functionality at P17. Finally, in MGC supernatants, the blocking antibody abolished the IGF-1 effect on active MMP-2 under normoxic and hypoxic conditions without affecting the extracellular levels of pro-MMP-2. These results demonstrate, for the first time, that the IGF-1/IGF-1R system regulates active MMP-2 levels in MGCs, thus contributing to MEC remodeling during the retinal neovascular process.

Simultaneous assessment of aberrant retinal vascularization, thickness, and function in an in vivo mouse oxygen-induced retinopathy model

“…When grouped correlations between vascular parameters and ERG parameters were evaluated regardless of flash intensity, b-wave peak time was positively correlated with percent retinal avascular area in only RA mice, which suggests that as the RA mice increased in vascular density with age, the b-wave peak time was also decreased. Our finding of prolonged b-wave peak times are somewhat consistent with prolonged b-wave peak times seen by Lorenc et al's (130 ms) bilateral ERGs at a flash intensity of 5 cd s/m 2 , 0.2 Hz (roughly 0.7 log cd s/m 2 ) in overnight dark-adapted P17 OIR mice compared with RA mice with peak times of 50 ms for both a and b-waves [13]. However, we found this prolonged b-wave peak times only in adult mice not neonatal.…”

“…It appeared that although the retinal veins physically recovered, both the retinal capillaries and inner retinal neuronal cells suffered permanent damage with ongoing attrition of unclear etiology, either owing to cell atrophy or arrested angiogenesis. Programmed cell death, atrophy, or loss from apoptosis have been reported as a cause of retinal thinning in OIR models of ROP and diabetic retinopathy [13,20,21] with retinal atrophy in the INL and the GCL [22,23], INL and IPL thinning [24], and neuronal apoptosis in avascular retinal regions with localized INL and IPL thinning [25]. Our in vivo studies of retinal structure highlight the vulnerability of the OIR inner retina contributing to long-standing vascular abnormalities.…”

“…Retinal neural, structural, and vascular development are related [9], and so ocular function could be affected by abnormal development of the retinal vessels [10,11]. Murine models of oxygen-induced retinopathy (OIR) have enhanced the understanding of molecular and cellular aspects of ROP [12,13]; but it is challenging to examine histological structures without sacrificing the animal. Recent in vivo studies using fluorescein angiography (FA) in live OIR mice have described tortuous retinal arteries, widened retinal veins, and reduced capillary density that vary with developmental maturity, with the eventual normalization of retinal vein width, but persistence of tortuosity and reduced capillary density in adult mice [14].…”

Metabolic Syndrome Triggered by Fructose Diet Impairs Neuronal Function and Vascular Integrity in ApoE-KO Mouse Retinas: Implications of Autophagy Deficient Activation

“…Electroretinographic activity was recorded after 2, 4, and 6 months of feeding according to previously described procedures ( Ridano et al, 2017 ; Lorenc et al, 2018 ; Subirada et al, 2019 ). Briefly, after overnight dark adaptation and under dim red illumination, mice were anesthetized with ketamine/xylazine (i.p.…”

A journey into the retina: Müller glia commanding survival and death

“…During the proliferative stage of retinopathy, IGF‐1 participates in neovessel formation by: Enhancing VEGF synthesis: The interaction of IGF‐1 with its membrane receptor (IGF‐1R) is able to activate the PI3‐Kinase and MAPK signalling pathways, which stabilize and accumulate hypoxia‐inducible factor (HIF)‐1α in the cytosol. Then, HIF‐1α translocates to the nucleus and induces gene expression, including VEGF (Treins, Giorgetti‐Peraldi, Murdaca, Monthouel‐Kartmann, & Van Obberghen, ). Stabilizing neovessel: IGF‐1 mediates the persistent activation of the ERK pathway to avoid newly formed neovessel disorganization (Jacobo & Kazlauskas, ). Remodelling the extracellular matrix: after ligand binding, IGF‐1R transduces intracellular signals that increase MMP‐2 activity in the proliferative phase, thereby contributing to the establishment of neovessels in the retina (Lorenc et al., ). There is a cooperative effect of ECs and MGCs to achieve remodelling, as both synthesize and secrete MMP‐2 to the milieu. …”