Ranibizumab Inhibits Human Tenon’s Fibroblast Proliferation via p21 Dependent p53 Mechanisms

Trabeculectomy is the gold standard procedure performed in glaucoma when topical medication and laser intervention failed. In a trabeculectomy, number of clinical trials have shown the efficacy of ranibizumab in minimizing extracellular matrix accumulation at the filtering site. Ranibizumab (LucentisTM) is a drug that targets vascular endothelial growth factor (VEGF). However, to date the actual mechanisms of this anti-VEGF in trabeculectomy is still not well understood. Hence, in here we aimed to elucidate the effects of ranibizumab on human Tenon’s fibroblast (HTF) isolated from patients undergoing trabeculectomy. In our previous study, we had reported that ranibizumab reduces the level of spermidine metabolite whereby spermidine is an important polyamine for cell proliferation. For this current study, cultured HTFs were divided into untreated, control IgG, ranibizumab only, difluoromethylornithine (DFMO; inhibitor of spermidine) only and ranibizumab with DFMO. All cells were extracted for PCR array (expression of CDKN1A, CDK2, and CDK4) and protein expression of p53, p21, CDK2, and CDK4 by Western Blot. In here, our result demonstrated that cells treated with ranibizumab or DFMO and cells treated with ranibizumab-DFMO have similar effects as both show increased in p53 and p21. Meanwhile, no significant differences in expression of CDKN1A, CDK2 and CDK4 were observed in all groups. In essence, our findings suggest that ranibizumab action is mediated by p21 and p53.

Important Metabolites in Maintaining Folate Cycle, Homocysteine, and Polyamine Metabolism Associated with Ranibizumab Treatment in Cultured Human Tenon's Fibroblasts

The anti-fibrotic properties of ranibizumab have been well documented. As an antagonist to vascular endothelial growth factor (VEGF), ranibizumab works by binding and neutralizing all active VEGF-A, thus limiting progressive cell growth and proliferation. Ranibizumab application in ocular diseases has shown remarkable desired effects; however, to date, its antifibrotic mechanism is not well understood. In this study, we identified metabolic changes in ranibizumab-treated human Tenon's fibroblasts (HTFs). Cultured HTFs were treated for 48 h with 0.5 mg/mL of ranibizumab and 0.5 mg/mL control IgG antibody which serves as a negative control. Samples from each group were injected into Agilent 6520 Q-TOF liquid chromatography/mass spectrometer (LC/MS) system to establish the metabolite expression in both ranibizumab treated cells and control group. Data obtained was analyzed using Agilent Mass Hunter Qualitative Analysis software to identify the most regulated metabolite following ranibizumab treatment. At p-value < 0.01 with the cut off value of two-fold change, 31 identified metabolites were found to be significantly upregulated in ranibizumab-treated group, with six of the mostly upregulated having insignificant role in fibroblast cell cycle and wound healing regulations. Meanwhile, 121 identified metabolites that were downregulated, and seven of the mostly downregulated are significantly involved in cell cycle and proliferation. Our findings suggest that ranibizumab abrogates the tissue scarring and wound healing process by regulating the expression of metabolites associated with fibrotic activity. In particular, we found that vitamin Bs are important in maintaining normal folate cycle, nucleotide synthesis, and homocysteine and spermidine metabolism. This study provides an insight into ranibizumab's mechanism of action in HTFs from the perspective of metabolomics.

Effects of ranibizumab on TGF-β1 and TGF-β2 production by human Tenon's fibroblasts: An in vitro study

PURPOSE

Inhibiting exaggerated wound healing responses, which are primarily mediated by human Tenon's fibroblast (HTF) migration and proliferation, has become the major determining factor for a successful trabeculectomy. Antivascular endothelial growth factor (anti-VEGF) has showed promising results as a potential antifibrotic candidate for use concurrently in trabeculectomy. Preliminary cohort studies have revealed improved bleb morphology following trabeculectomy augmented with ranibizumab. However, the effects on HTFs remain unclear. This study was conducted to understand the effects of ranibizumab on transforming growth factor (TGF)-β1 and transforming growth factor (TGF)-β2 expression by HTFs.

METHODS

The effect of ranibizumab on HTF proliferation and cell viability was determined using 3-(4,5-dimethylthiazone-2-yl)-2,5-diphenyl tetrazolium (MTT) assay. Ranibizumab at concentrations ranging from 0.01 to 0.5 mg/ml were administered for 24, 48, and 72 h in serum and serum-free conditions. Supernatants and cell lysates from samples were assessed for TGF-β1 and TGF-β2 mRNA and protein levels using quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA).

RESULTS

At 48 h, 0.5 mg/ml of ranibizumab significantly induced cell death under serum-free culture conditions (p<0.05). Ranibizumab caused a significant reduction in TGF-β1 mRNA, but not for TGF-β2. However, the total protein production of TGF-β1 and TGF-β2 was unaffected by this anti-VEGF treatment.

CONCLUSIONS

Exposure of HTFs to an intravitreal dose of ranibizumab significantly suppresses cell viability in vitro; however, the application seemed unable to affect the ultimate production of TGF-β. Therefore, we highlighted ranibizumab as a potential antiscarring agent that acts via a different mechanism when used synergistically with another antifibrotic agent. Understanding the mechanism of actions of ranibizumab offers an additional view of a possible new rational therapeutic strategy.