Intravitreal aflibercept for macular oedema secondary to central retinal vein occlusion in patients with prior treatment with bevacizumab or ranibizumab.

PurposeTo report the visual and anatomic outcomes in eyes with macular oedema (MO) secondary to central retinal vein occlusion (CRVO) that were switched from either intravitreal bevacizumab or ranibizumab to intravitreal aflibercept.MethodsTwo-center retrospective chart review. Eyes with MO secondary to CRVO that received a minimum of three intravitreal injections of bevacizumab or ranibizumab and were switched to intravitreal aflibercept for persistent or recurrent MO not responding to either bevacizumab and/or ranibizumab.ResultsIn all 42 eyes of 42 patients were included in the study. The median visual acuity before the switch was 20/126, 1 month after the first injection of aflibercept 20/89 (P=0.0191), and at the end of the follow-up 20/100 (P=0.2724). The median CRT before the switch was 536 µm, 1 month after the first injection of aflibercept 293.5 µm (P=0.0038), and at the end of the follow-up 279 µm (P=0.0013 compared to before the switch). The median number of weeks between injections before the switch was 5.6 and after the switch was 7.6 (P<0.0001).ConclusionConverting eyes with refractory MO due to CRVO to aflibercept can result in stabilization of the vision, improved macular anatomy, and extension of the injection interval.

Necrotic enlargement of cone photoreceptor cells and the release of high-mobility group box-1 in retinitis pigmentosa.

Retinitis pigmentosa (RP) refers to a group of inherited retinal degenerations resulting form rod and cone photoreceptor cell death. The rod cell death due to deleterious genetic mutations has been shown to occur mainly through apoptosis, whereas the mechanisms and features of the secondary cone cell death have not been fully elucidated. Our previous study showed that the cone cell death in rd10 mice, an animal model of RP, involves necrotic features and is partly mediated by the receptor interacting protein kinase. However, the relevancy of necrotic cone cell death in human RP patients remains unknown. In the present study, we showed that dying cone cells in rd10 mice exhibited cellular enlargement, along with necrotic changes such as cellular swelling and mitochondrial rupture. In human eyes, live imaging of cone cells by adaptive optics scanning laser ophthalmoscopy revealed significantly increased percentages of enlarged cone cells in the RP patients compared with the control subjects. The vitreous of the RP patients contained significantly higher levels of high-mobility group box-1, which is released extracellularly associated with necrotic cell death. These findings suggest that necrotic enlargement of cone cells is involved in the process of cone degeneration, and that necrosis may be a novel target to prevent or delay the loss of cone-mediated central vision in RP.

Membrane-bound and soluble Fas ligands have opposite functions in photoreceptor cell death following separation from the retinal pigment epithelium.

Fas ligand (FasL) triggers apoptosis of Fas-positive cells, and previous reports described FasL-induced cell death of Fas-positive photoreceptors following a retinal detachment. However, as FasL exists in membrane-bound (mFasL) and soluble (sFasL) forms, and is expressed on resident microglia and infiltrating monocyte/macrophages, the current study examined the relative contribution of mFasL and sFasL to photoreceptor cell death after induction of experimental retinal detachment in wild-type, knockout (FasL-/-), and mFasL-only knock-in (ΔCS) mice. Retinal detachment in FasL-/- mice resulted in a significant reduction of photoreceptor cell death. In contrast, ΔCS mice displayed significantly more apoptotic photoreceptor cell death. Photoreceptor loss in ΔCS mice was inhibited by a subretinal injection of recombinant sFasL. Thus, Fas/FasL-triggered cell death accounts for a significant amount of photoreceptor cell loss following the retinal detachment. The function of FasL was dependent upon the form of FasL expressed: mFasL triggered photoreceptor cell death, whereas sFasL protected the retina, indicating that enzyme-mediated cleavage of FasL determines, in part, the extent of vision loss following the retinal detachment. Moreover, it also indicates that treatment with sFasL could significantly reduce photoreceptor cell loss in patients with retinal detachment.

Macrophage- and RIP3-dependent inflammasome activation exacerbates retinal detachment-induced photoreceptor cell death.

Detachment of photoreceptors from the retinal pigment epithelium is seen in various retinal disorders, resulting in photoreceptor death and subsequent vision loss. Cell death results in the release of endogenous molecules that activate molecular platforms containing caspase-1, termed inflammasomes. Inflammasome activation in retinal diseases has been reported in some cases to be protective and in others to be detrimental, causing neuronal cell death. Moreover, the cellular source of inflammasomes in retinal disorders is not clear. Here, we demonstrate that patients with photoreceptor injury by retinal detachment (RD) have increased levels of cleaved IL-1ß, an end product of inflammasome activation. In an animal model of RD, photoreceptor cell death led to activation of endogenous inflammasomes, and this activation was diminished by Rip3 deletion. The major source of Il1b expression was found to be infiltrating macrophages in the subretinal space, rather than dying photoreceptors. Inflammasome inhibition attenuated photoreceptor death after RD. Our data implicate the infiltrating macrophages as a source of damaging inflammasomes after photoreceptor detachment in a RIP3-dependent manner and suggest a novel therapeutic target for treatment of retinal diseases.

Mammalian STE20-like kinase 2, not kinase 1, mediates photoreceptor cell death during retinal detachment.

Photoreceptor cell death is the definitive cause of vision loss in retinal detachment (RD). Mammalian STE20-like kinase (MST) is a master regulator of both cell death and proliferation and a critical factor in development and tumorigenesis. However, to date the role of MST in neurodegeneration has not been fully explored. Utilizing MST1(-/-) and MST2(-/-) mice we identified MST2, but not MST1, as a regulator of photoreceptor cell death in a mouse model of RD. MST2(-/-) mice demonstrated significantly decreased photoreceptor cell death and outer nuclear layer (ONL) thinning after RD. Additionally, caspase-3 activation was attenuated in MST2(-/-) mice compared to control mice after RD. The transcription of p53 upregulated modulator of apoptosis (PUMA) and Fas was also reduced in MST2(-/-) mice post-RD. Retinas of MST2(-/-) mice displayed suppressed nuclear relocalization of phosphorylated YAP after RD. Consistent with the reduction of photoreceptor cell death, MST2(-/-) mice showed decreased levels of proinflammatory cytokines such as monocyte chemoattractant protein 1 and interleukin 6 as well as attenuated inflammatory CD11b cell infiltration during the early phase of RD. These results identify MST2, not MST1, as a critical regulator of caspase-mediated photoreceptor cell death in the detached retina and indicate its potential as a future neuroprotection target.

Programmed necrosis, not apoptosis, is a key mediator of cell loss and DAMP-mediated inflammation in dsRNA-induced retinal degeneration.

There is no known treatment for the dry form of an age-related macular degeneration (AMD). Cell death and inflammation are important biological processes thought to have central role in AMD. Here we show that receptor-interacting protein (RIP) kinase mediates necrosis and enhances inflammation in a mouse model of retinal degeneration induced by dsRNA, a component of drusen in AMD. In contrast to photoreceptor-induced apoptosis, subretinal injection of the dsRNA analog poly(I : C) caused necrosis of the retinal pigment epithelium (RPE), as well as macrophage infiltration into the outer retinas. In Rip3(-/-) mice, both necrosis and inflammation were prevented, providing substantial protection against poly(I : C)-induced retinal degeneration. Moreover, after poly(I : C) injection, Rip3(-/-) mice displayed decreased levels of pro-inflammatory cytokines (such as TNF-α and IL-6) in the retina, and attenuated intravitreal release of high-mobility group box-1 (HMGB1), a major damage-associated molecular pattern (DAMP). In vitro, poly(I : C)-induced necrosis were inhibited in Rip3-deficient RPE cells, which in turn suppressed HMGB1 release and dampened TNF-α and IL-6 induction evoked by necrotic supernatants. On the other hand, Rip3 deficiency did not modulate directly TNF-α and IL-6 production after poly(I : C) stimulation in RPE cells or macrophages. Therefore, programmed necrosis is crucial in dsRNA-induced retinal degeneration and may promote inflammation by regulating the release of intracellular DAMPs, suggesting novel therapeutic targets for diseases such as AMD.