PURPOSE. Ciliary neurotrophic factor (CNTF) is a well-characterized neurotrophic factor currently in clinical trials for the treatment of macular telangiectasia type II. Our previous work showed that CNTF-induced STAT3 signaling is a potent inhibitor of pathologic preretinal neovascular tuft formation in the mouse model of oxygen-induced retinopathy. In this study, we investigated the effect of CNTF on outer retinal and choroidal angiogenesis and the mechanisms that underpin the observed decrease in outer retinal neovascularization following CNTF treatment. METHODS. In the Vldlr-/and laser-CNV mouse models, mice received a one-time injection (on postnatal day [P] 12 in the Vldlr-/model and 1 day after laser in the Choroidal Neovascularization (CNV) model) of recombinant CNTF or CxCl10, and the extent of neovascular lesions was assessed 6 days posttreatment. STAT3 downstream targets affected by CNTF treatment were identified using quantitative PCR analysis. A proteome array was used to compare media conditioned by CNTF-treated and control-treated primary Müller cells to screen for CNTF-induced changes in secreted angiogenic factors. RESULTS. Intravitreal treatment with recombinant CNTF led to significant reduction in neovascularization in the Vldlr-/and laser-CNV mouse models. Treatment effect in the Vldlr-/was long-lasting but time sensitive, requiring intravitreal treatment before P19. Mechanistic workup in vitro as well as in vivo confirmed significant activation of the STAT3-signaling pathway in Müller cells in response to CNTF treatment and upregulation of CxCl10. Intravitreal injections of recombinant CxCl10 significantly reduced outer retinal neovascularization in vivo in both the Vldlr-/and laser-CNV mouse models. CONCLUSIONS. CNTF treatment indirectly affects outer retinal and choroidal neovascularization by inducing CxCl10 secretion from retinal Müller cells.
Aberrant angiogenesis is a hallmark of cardiovascular and retinal neovascular disease. The STAT3 pathway represents a potential pharmacological target for those diseases due to its impact on angiogenesis. Surprisingly some STAT3 activators including the IL6 cytokine member oncostatin M (OSM) enhance angiogenesis whereas others like ciliary neurotropic factor (CNTF) reduce it. This study aims to clarify those conflicting effects. In contrast to the antiangiogenic cytokine CNTF, the proangiogenic OSM was able to activate intracellular signaling pathways beyond STAT3 including ERK and AKT. These differences translated into transcriptomic and metabolic shifts. siRNA mediated STAT3 knockdown experiments showed a decrease in VEGF-induced endothelial migration and sprouting while enhancing OSMs proangiogenic drive and switching CNTF's antiangiogenic to a proangiogenic response. These effects correlated with a transcriptomic shift representing enhanced STAT1 and ERK activity following STAT3 knockdown including a compensatory prolonged pSTAT1 activity. In conclusion, the angiogenic effect of STAT3 seems to be determined by cytokine-induced STAT3 specificity and simultaneous activity of other intracellular signaling pathways while the STAT3 pathway, predominantly recognized for its proangiogenic phenotypes, reveals novel antiangiogenic potential.
Limbal stem cell deficiency (LSCD) is a complex, multifactorial disease affecting limbal epithelial progenitor cells (LEPC), which are essential for maintaining corneal stability and transparency. Human induced pluripotent stem cell-derived (hiPSC-) LEPC are a promising cell source for the treatment of LSCD. However, their similarity to native tissue-derived (T-) LEPC and their functional characterization has not been studied in detail. Here, we show that hiPSC-LEPC and T-LEPC have rather similar gene expression patterns, colony-forming ability, wound-healing capacity, and melanosome uptake. In addition, hiPSC-LEPC exhibited lower immunogenicity and reduced the proliferation of peripheral blood mononuclear cells compared with T-LEPC. Similarly, the hiPSC-LEPC secretome reduced the proliferation of vascular endothelial cells more than the T-LEPC secretome. Moreover, hiPSC-LEPC successfully repopulated decellularized human corneolimbal (DHC/L) scaffolds with multilayered epithelium, while basal deposition of fibrillary material was observed. These findings suggest that hiPSC-LEPC exhibited functional properties close to native LEPC and that hiPSC-LEPC-DHC/L scaffolds might be feasible for transplantation in patients suffering from LSCD in the future. Although hiPSC-LEPC-based stem cell therapy is promising, the current study also revealed new challenges, such as abnormal extracellular matrix deposition, that need to be overcome before hiPSC-LEPC-based stem cell therapies are viable.
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