Ischaemia-induced retinal neovascularisation and diabetic retinopathy in mice with conditional knockout of hypoxia-inducible factor-1 in retinal Müller cells

Abstract

Aims/hypothesis Retinal Müller cells are known to produce inflammatory and angiogenic cytokines, which play important roles in diabetic retinopathy. Hypoxia-inducible factor (HIF)-1 has been shown to play a crucial role in retinal inflammation and neovascularisation. We sought to determine the role of Müller cell-derived HIF-1 in oxygeninduced retinopathy (OIR) and diabetic retinopathy using conditional Hif-1α (also known as Hif1a) knockout (KO) mice. Methods Conditional Hif-1α KO mice were generated by crossing mice expressing cyclisation recombinase (cre, also known as P1_gp003) in Müller cells with floxed Hif-1α mice and used for OIR and streptozotocin-induced diabetes to induce retinal neovascularisation and inflammation, respectively. Abundance of HIF-1α and pro-angiogenic and pro-inflammatory factors was measured by immunoblotting and immunohistochemistry. Retinal neovascularisation was visualised by angiography and quantified by counting pre-retinal nuclei. Retinal inflammation was evaluated by leucostasis and vascular leakage. Results While the Hif-1α KO mice showed significantly decreased HIF-1α levels in the retina, they exhibited no apparent histological or visual functional abnormalities (2011( ) 54:1554( -1566( DOI 10.1007( /s00125-011-2081 under normal conditions. Compared with wild-type counterparts, Hif-1α KO mice with OIR demonstrated attenuated overproduction of vascular endothelial growth factor (VEGF) and intercellular adhesion molecule (ICAM)-1, reduced vascular leakage and alleviated neovascularisation in the retina. Under diabetes conditions, disruption of Hif-1α in Müller cells attenuated the increases of retinal vascular leakage and adherent leucocytes, as well as the overproduction of VEGF and ICAM-1. Conclusions/interpretation Müller cell-derived HIF-1α is a key mediator of retinal neovascularisation, vascular leakage and inflammation, the major pathological changes in diabetic retinopathy. Müller cell-derived HIF-1α is therefore a promising therapeutic target for diabetic retinopathy.

Neural inflammation and the microglial response in diabetic retinopathy

“…Interestingly, TNF-α expression was found to be elevated in the retinas of diabetic wild-type mice but not in VEGF-A knockouts. Similar results were obtained by Lin and coworkers when they observed that Müller cell-specific disruption of the hypoxia-inducible factor 1 gene resulted in diminished expression of VEGF and ICAM-1, as well as reduced leukostasis and vascular permeability in mice made diabetic with STZ [44].…”

Calcium mediates high glucose-induced HIF-1α and VEGF expression in cultured rat retinal Müller cells through CaMKII-CREB pathway

“…Over the past decade, almost all retinal cells have been shown to express HIF-1α and VEGF in DR. In this context, recent studies using conditional KO mice models have suggested that the Müller cell-derived HIF-1α and VEGF has a causative role in the major pathologic changes in DR [27,28] . Increasing evidence suggests that hyperglycemia induces changes in the retinal [Ca 2+ ] i dynamics [2,4] , which have been associated with distinct pathological processes, such as DR.…”

Neuroinflammation and Neurodegenerative Disorders of the Retina

“…Mice with streptozotocin (STZ)-induced diabetes show elevated VEGF levels in the retina; however, this increase was not seen in mice with a conditional knockout of hypoxiainducible factor-1α (HIF-1α) in the Müller glial cells. Moreover, when the same mice were tested in the oxygen-induced retinopathy model, in which retinal neovascularization occurs in response to excessive VEGF expression, the HIF-1α deficiency decreased the pathological neovascularization in the retina [26]. Other group also reported that Müller glial cell-derived VEGF is essential for diabetes-induced retinal inflammation and vascular leakage [27].…”

“…Interleukin-6 (IL-6) mRNA is expressed in the retinal ganglion cells and inner nuclear layer cells, including the Müller glial cells [25]. Retinal ganglion cells express additional cytokines such as vascular endothelial growth factor (VEGF) [26], which contributes to the pathogenesis of diabetic retinopathy. Mice with streptozotocin (STZ)-induced diabetes show elevated VEGF levels in the retina; however, this increase was not seen in mice with a conditional knockout of hypoxiainducible factor-1α (HIF-1α) in the Müller glial cells.…”