Estudio de la degeneración y neuroprotección retiniana: taurina, terapia celular, reacción glial e inyecciones intravítreas de anticuerpos anti-VEGF

Abstract

Introduction: Degenerative diseases of retinal photoreceptors comprise a heterogeneous group of retinal pathologies caused by environmental and/or genetic factors that lead to irreversible blindness. In this Doctoral Thesis, we investigate the effects of various experimental interventions on the retina of normal rats or those with hereditary or induced photoreceptor degeneration. Objectives: We studied: I) in the retina of normal albino rats, the adverse effects of intravitreal injections (IVI) of PBS, ranibizumab, aflibercept, and a rat anti-VEGF; II) in albino rats with phototoxic retinal degeneration, the role of glia in photoreceptor degeneration; III) in the retina of normal albino rats, the effect of taurine nutritional deficiency; IV) in Royal College of Surgeons (RCS) rats, the effect of taurine dietary supplementation; V) in RCS and P23H-1 rats, the effect of syngeneic cell therapy (intravitreal or subretinal) with bone marrow-derived mononuclear cells (BM-MNC). Methods: Adult Sprague-Dawley rats were used for objectives I, II, and III; RCS rats for objective IV; and RCS and P23H-1 rats for objective V. For objective III, taurine deficiency was induced by administering 3% β-alanine in the water, and for objectives II and IV, phototoxic retinal degeneration was induced. Retinas were processed as whole mounts or cross-sectioned and immunodetected to label S and L/M cones, microglial and macroglial cells, retinal ganglion cells (RGCs), intrinsically photosensitive RGCs (ipRGCs), synaptic connections, and cellular oxidative stress. Results: I) All IVIs triggered glial cell activation, which was greater with higher concentrations of ranibizumab and aflibercept, also causing RGC death but not ipRGC death; II) Phototoxicity produces rings of cone degeneration showing activated microglial and Müller cells; III) Taurine depletion induces photoreceptor degeneration, microglial activation, oxidative stress, synaptic loss, and impaired phagocytic capacity of the retinal pigment epithelium (RPE), and these effects are exacerbated by light exposure; IV) Taurine supplementation in the diet of RCS rats decreases microglial activation, synaptic degeneration, and oxidative stress, increases RPE phagocytosis, and improves electroretinographic responses; V) Intravitreal or subretinal injections of BM-MNCs in RCS and P23H-1 rats increase photoreceptor survival and reduce synaptic degeneration but do not alter microglial cell activation or migration, nor do they improve electroretinographic responses. Conclusions: I) IVIs of all substances have inflammatory effects on the retina of adult rats, which are more pronounced when humanized substances are used at high doses, causing severe inflammation and RGC death but not ipRGC death; II) Microglial cells and Müller cells have coordinated actions in photoreceptor phagocytosis, retinal remodeling, and the formation of glial seals; III) Taurine depletion in the rat retina induces photoreceptor and RGC death, impaired phagocytosis by RPE cells, and increased susceptibility of photoreceptors to phototoxic damage; IV) Taurine supplementation in the diet of RCS rats decreases microglial activation, photoreceptor degeneration, oxidative stress, and improves retinal function; V) Intravitreal and subretinal transplantation of syngeneic BM-MNCs reduces photoreceptor degeneration but does not improve retinal function.