Effects of intravitreal injection of siRNA against caspase-2 on retinal and optic nerve degeneration in air blast induced ocular trauma

Abstract

Ocular repeated air blast injuries occur from low overpressure blast wave exposure, which are often repeated and in quick succession. We have shown that caspase-2 caused the death of retinal ganglion cells (RGC) after blunt ocular trauma. Here, we investigated if caspase-2 also mediates RGC apoptosis in a mouse model of air blast induced indirect traumatic optic neuropathy (b-ITON). C57BL/6 mice were exposed to repeated blasts of overpressure air (3 × 2 × 15 psi) and intravitreal injections of siRNA against caspase-2 (siCASP2) or against a control enhanced green fluorescent protein (siEGFP) at either 5 h after the first 2 × 15 psi (“post-blast”) or 48 h before the first blast exposure (“pre-blast”) and repeated every 7 days. RGC counts were unaffected by the b-ITON or intravitreal injections, despite increased degenerating ON axons, even in siCASP2 “post-blast” injection groups. Degenerating ON axons remained at sham levels after b-ITON and intravitreal siCASP2 “pre-blast” injections, but with less degenerating axons in siCASP2 compared to siEGFP-treated eyes. Intravitreal injections “post-blast” caused greater vitreous inflammation, potentiated by siCASP2, with less in “pre-blast” injected eyes, which was abrogated by siCASP2. We conclude that intravitreal injection timing after ocular trauma induced variable retinal and ON pathology, undermining our candidate neuroprotective therapy, siCASP2.

MicroRNA profile of extracellular vesicles released by Müller glial cells

“…Whilst the PI3K/AKT pathway is active in developing tissue and is a source for complete axon regeneration in the peripheral nervous system ( Saiijilafu et al, 2013 ; Zhang et al, 2014 ), its activity is suppressed in quiescent cells by the phosphoenzyme PTEN. Previous studies suggest that the direct suppression of PTEN, CASP2, and related pro-apoptotic genes by miRNA overexpression or synthetic siRNA delivery is capable of preventing the autophagy of neurons in rodent models of RGC depletion ( Li et al, 2018 ; Thomas et al, 2021 ). It is therefore possible that a miRNA-induced downregulation of PTEN and subsequent activation of PI3K/AKT signalling may contribute to the neuroprotective effects attributed to Müller following whole cell transplantation studies ( Singhal et al, 2012 ; Eastlake et al, 2019 ).…”

Traumatic Optic Neuropathy: Update on Management

“…The upregulation of epidermal growth factor receptor pathways by inhibiting miR-21 has also been shown to promote axonal regeneration of RGCs in a rat model of optic nerve injury (ONI) [ 113 ]. Intravitreal injection of siRNA against caspase-2 has not been found to protect RGCs from ONI in the mouse model [ 114 ]. However, in ONI therapy, miRNAs remain a promising tool.…”

Optic nerve diseases and regeneration: How far are we from the promised land?

“…47,48 Intravitreal injection of siRNA for caspase-2 enhances RGC survival rate. 46 Apoptotic protease activating factor-1 (APAF-1) is a key mediator of caspase-induced cell death. siRNA-based knockdown of APAF-1 also improved RGC survival.…”

“…Endogenous and exogenous apoptosis pathway involves activation of different caspases, which are a family of protease enzymes playing essential roles in programmed cell death. Active caspase‐2, 46 −3, and −9 are found to be involved in RGC death after ONI 47 . Intraocular injection of caspase‐3 or capase‐9 inhibitors promotes modest protection of RGCs against optic nerve transection‐induced apoptosis 47,48 .…”

“…Intraocular injection of caspase‐3 or capase‐9 inhibitors promotes modest protection of RGCs against optic nerve transection‐induced apoptosis 47,48 . Intravitreal injection of siRNA for caspase‐2 enhances RGC survival rate 46 . Apoptotic protease activating factor‐1 (APAF‐1) is a key mediator of caspase‐induced cell death.…”