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Matrix metalloproteinases in the mouse retina: a comparative study of expression patterns and MMP antibodies
Lies De Groef1, Lien Andries2, Kim Lemmens3
1Laboratory of Neural Circuit Development and Regeneration, Animal Physiology and Neurobiology Section, Department of Biology; KU Leuven, Naamsestraat 61, Box 2464, B-3000, Leuven, Belgium. lies.degroef@bio.kuleuven.be.
Background:
Matrix metalloproteinases (MMPs), a family of Zn(2+)-dependent endoproteases, have been shown to act as fine regulators of both health and disease. Limited research revealed that they are essential to maintaining ocular physiology and inordinate MMP activities have been linked to several neurodegenerative disorders of the retina, including age-related macular degeneration, proliferative diabetic retinopathy and glaucomatous optic neuropathies (GONs). Nevertheless, a clear definition of their pathology-exacerbating and/or -resolving actions is lacking, especially in the context of GONs, as most studies thus far merely focused on expression profiling in human patients. Therefore, in an initial step towards an improved understanding of MMP functions in the retina, we studied the spatial expression pattern of MMP-2, -3, -9 and MT1-MMP in the healthy mouse retina.
Methods:
The spatial expression pattern of MMP-2, -3, -9 and MT1-MMP was studied in the healthy mouse retina via immunohistochemical stainings, and immunoreactivity profiles were compared to existing literature. Moreover, we considered sensitivity and specificity issues with commercially available MMP antibodies via Western blot.
Results:
Basal expression of MMP-2,-3, -9 and MT1-MMP was found in the retina of healthy, adult mice. MMP-2 expression was seen in Müller glia, predominantly in their end feet, which is in line with available literature. MMP-3 expression was described for the first time in the retina, and was observed in vesicle-like structures along the radial fibers of Müller glia. MMP-9 expression, about which still discords exists, was seen in microglia and in a sparse subset of (apoptosing) RGCs. MT1-MMP localization was for the first time studied in adult mice and was found in RGC axons and Müller glia, mimicking the MT1-MMP expression pattern seen in rabbits and neonatal mice. Moreover, one antibody was selected for each MMP, based on its staining pattern in Western blot.
Conclusions:
The present MMP immunoreactivity profiles in the mouse retina and validation of MMP antibodies, can be instrumental to study MMP expression in mouse models of ocular pathologies and to compare these expression profiles to observations from clinical studies, which would be a first step in the disentanglement of the exact role MMPs in ocular/retinal diseases.
Insights
This study maps the expression of matrix metalloproteinases (MMPs) in healthy mouse retinas. Findings reveal specific MMP locations, aiding research into retinal diseases like glaucoma.
Area of Science:
- Ophthalmology and Neuroscience
- Molecular and Cellular Biology
- Enzyme Function and Regulation
Background:
- Matrix metalloproteinases (MMPs) are critical regulators in physiological and pathological processes.
- While essential for ocular health, aberrant MMP activity is implicated in retinal neurodegenerative diseases such as glaucoma.
- Current understanding of MMP roles in glaucomatous optic neuropathies (GONs) is limited, with a need for detailed expression profiling.
Purpose of the Study:
- To investigate the spatial expression patterns of MMP-2, MMP-3, MMP-9, and MT1-MMP in the healthy adult mouse retina.
- To establish a baseline understanding of MMP distribution to facilitate future studies on ocular pathologies.
- To validate the specificity and sensitivity of commercially available MMP antibodies for retinal research.
Main Methods:
- Immunohistochemical staining was employed to determine the spatial expression of MMP-2, MMP-3, MMP-9, and MT1-MMP in healthy mouse retinas.
- Western blot analysis was performed to assess the sensitivity and specificity of antibodies used for MMP detection.
- Expression profiles were compared with existing literature and validated across different species and developmental stages where applicable.
Main Results:
- Basal expression of MMP-2, MMP-3, MMP-9, and MT1-MMP was detected in healthy adult mouse retinas.
- MMP-2 localized to Müller glia end feet; MMP-3 was newly identified in Müller glia radial fibers; MMP-9 was found in microglia and apoptotic retinal ganglion cells (RGCs).
- MT1-MMP was observed in RGC axons and Müller glia, consistent with patterns in rabbits and neonatal mice. Antibody validation confirmed selection of one antibody per MMP.
Conclusions:
- The established MMP immunoreactivity profiles provide a crucial foundation for studying MMP expression in mouse models of retinal diseases.
- These findings will enable comparative analysis between experimental models and clinical observations, aiding in understanding MMPs' roles in ocular pathologies.
- This work represents a significant first step toward clarifying the precise functions of MMPs in the pathogenesis and resolution of retinal diseases.
