Fractalkine isoforms differentially regulate microglia-mediated inflammation and enhance visual function in the
Derek Rodriguez1, Kaira A Church1, Alicia N Pietramale1
1Department of Molecular Microbiology and Immunology, UTSA Circle, The University of Texas at San Antonio, San Antonio, TX, 78249, USA.
Abstract:
Diabetic retinopathy (DR) affects about 200 million people worldwide, causing leakage of blood components into retinal tissues, leading to activation of microglia, the resident phagocytes of the retina, promoting neuronal and vascular damage. The microglial receptor, CX3CR1, binds to fractalkine (FKN), an anti-inflammatory chemokine that is expressed on neuronal membranes (mFKN), and undergoes constitutive cleavage to release a soluble domain (sFKN). Deficiencies in CX3CR1 or FKN showed increased microglial activation, inflammation, vascular damage, and neuronal loss in experimental mouse models. To understand the mechanism that regulates microglia function, recombinant adeno-associated viral vectors (rAAV) expressing mFKN or sFKN were delivered to intact retinas prior to diabetes. High-resolution confocal imaging and mRNA-seq were used to analyze microglia morphology and markers of expression, neuronal and vascular health, and inflammatory mediators. We confirmed that prophylactic intra-vitreal administration of rAAV expressing sFKN (rAAV-sFKN), but not mFKN (rAAV-mFKN), in FKNKO retinas provided vasculo- and neuro-protection, reduced microgliosis, mitigated inflammation, improved overall optic nerve health by regulating microglia-mediated inflammation, and prevented fibrin(ogen) leakage at 4 weeks and 10 weeks of diabetes induction. Moreover, administration of sFKN improved visual acuity. Our results elucidated a novel intervention via sFKN gene therapy that provides an alternative pathway to implement translational and therapeutic approaches, preventing diabetes-associated blindness.
Insights
Soluble fractalkine (sFKN) gene therapy protected against diabetic retinopathy (DR) by regulating microglia and reducing inflammation. This approach offers a novel therapeutic strategy to prevent diabetes-associated blindness.
Area of Science:
- Ophthalmology
- Neuroscience
- Immunology
Background:
- Diabetic retinopathy (DR) affects 200 million people globally, causing retinal tissue damage via microglial activation and inflammation.
- The fractalkine (FKN) and CX3CR1 pathway is crucial for regulating microglial function; deficiencies exacerbate DR pathology.
- Understanding microglia regulation is key to developing effective DR treatments.
Purpose of the Study:
- To investigate the therapeutic potential of soluble fractalkine (sFKN) gene therapy in preventing diabetic retinopathy.
- To elucidate the mechanisms by which sFKN influences microglial activation, inflammation, and retinal health in a diabetes model.
Main Methods:
- Recombinant adeno-associated viral vectors (rAAV) expressing membrane-bound FKN (mFKN) or sFKN were administered to retinas.
- High-resolution confocal imaging and mRNA sequencing were employed to analyze retinal tissues.
- Evaluated microglia morphology, gene expression, neuronal and vascular health, and inflammatory markers in diabetic mouse models.
Main Results:
- Prophylactic intra-vitreal administration of rAAV-sFKN, but not rAAV-mFKN, protected vasculature and neurons in FKN knockout retinas.
- rAAV-sFKN treatment reduced microgliosis, mitigated inflammation, and improved optic nerve health.
- sFKN therapy prevented fibrin(ogen) leakage and improved visual acuity in diabetic mice.
Conclusions:
- Soluble fractalkine (sFKN) gene therapy offers a novel neuroprotective and vasculoprotective approach for diabetic retinopathy.
- sFKN regulates microglia-mediated inflammation, presenting a promising translational strategy to prevent diabetes-associated blindness.
