Intravitreal bevacizumab in the treatment of diabetic ocular neovascularization

Association between the response of intravitreal antivascular endothelial growth factor injection and systemic factors of diabetic macular edema

BACKGROUND

This study investigated the effects of systemic factors in response to intravitreal injections in patients with macular edema due to non-proliferative diabetic retinopathy (NPDR).

METHODS

We retrospectively reviewed the medical records of patients treated with intravitreal injections for macular edema secondary to NPDR between January 2018 and January 2021. The patients were divided into three groups according to the injection response. When patients with diabetic macular edema showed 20µ or more reduction in central retinal thickness compared to baseline, they were classified as responsive group, and if not, they were classified as refractory group. The responsive group was further divided into the complete and incomplete response groups. Patients with complete disappearance of edema at seven months were classified as the complete response group, whereas those in which edema did not disappear were classified as the incomplete response group. The clinical characteristics of each group, including medical history, ophthalmic examination results, and laboratory examination results at the time of diagnosis, were analyzed.

RESULTS

Of the 112 eyes (91 patients) that satisfied the inclusion criteria, 89 (77 patients) in the responsive group and 23 (14 patients) in the refractory group were included in the analysis. The responsive group was further divided into the complete (51 eyes) and incomplete (38 eyes) response groups. The refractory group had significantly higher glycated hemoglobin levels and significantly lower estimated glomerular filtration rates than the responsive group (p = 0.026 and p = 0.012, respectively). In the multivariate logistic regression analysis, both factors were found to be significant in predicting the degree of response (all p < 0.05). No factor showed a significant difference between the incomplete and complete response groups(all p > 0.05).

CONCLUSIONS

In macular edema caused by NPDR, low glomerular filtration rates and high glycated hemoglobin levels may be used as predictors of poor response to intravitreal injection therapy. In addition to blood glucose control, education should be provided regarding the need for the continuous monitoring of renal function.

TIME COURSE OF CHANGES IN OPTIC DISK NEOVASCULARIZATION AFTER A SINGLE INTRAVITREAL BEVACIZUMAB INJECTION

PURPOSE

To evaluate the longitudinal changes in optic disk neovascularization (NVD) after intravitreal bevacizumab injection using optical coherence tomography angiography.

METHODS

In this prospective, interventional, case series, eyes with NVD secondary to diabetic retinopathy were enrolled. En face optical coherence tomography angiographic images were obtained from the optic disks before and 3 hours, 6 hours, 24 hours, 7 days, and 30 days after intravitreal bevacizumab injection. The size and flow area of the neovascularization were measured by two graders.

RESULTS

Eleven eyes of 9 patients with a mean age of 52.11 ± 9.48 years were included. The reduction in the NVD size and flow area was statistically significant at 24 hours, 7 days, and 30 days after injections compared with the baseline measurements (all P < 0.05). The decremental regression in the NVD size and flow area continued during the study course. The changes were not statistically significant in 3-hour and 6-hour measurements (all P > 0.05).

CONCLUSION

In this study, statistically significant regression in the NVD size and flow area was observed as early as 24 hours after a single intravitreal bevacizumab injection, with a continued decreasing trend for at least a 1-month period.

Lutein and zeaxanthin attenuates VEGF-induced neovascularisation in human retinal microvascular endothelial cells through a Nox4-dependent pathway

Age-related macular degeneration (AMD) and proliferative diabetic retinopathy (DR) are two of the most common and severe causes of vision loss in the population. Both conditions are associated with excessive levels of vascular endothelial growth factor (VEGF) in the eye which results in an increase in the formation of new blood vessels through a process called neovascularisation. As such, anti-VEGF therapies are currently utilised as a treatment for patients with AMD however they are associated with painful administration of injections and potential degeneration of healthy endothelium. There is therefore growing interest in alternate treatment options to reduce neovascularisation in the eye. The use of carotenoids, lutein (L) and zeaxanthin (Z), has been shown to improve vision loss parameters in patients with AMD, however the underlying mechanisms are not well-understood. We studied the impact of these compounds on neovascularisation processes using an in vitro cell model of the retinal microvascular endothelium. Our findings show that L and Z reduced VEGF-induced tube formation whilst, in combination (5:1 ratio), the compounds significantly blocked VEGF-induced neovascularisation. The carotenoids, individually and in combination, reduced VEGF-induced oxidative stress concomitant with increased activity of the NADPH oxidase, Nox4. We further demonstrated that the Nox4 inhibitor, GLX7013114, attenuated the protective effect of L and Z. Taken together, these findings indicate the protective effect of the carotenoids, L and Z, in reducing VEGF-mediated neovascularisation via a Nox4-dependent pathway. These studies implicate the potential for these compounds to be used as a therapeutic approach for patients suffering from AMD and proliferative DR.

Observation of optic disc neovascularization using OCT angiography in proliferative diabetic retinopathy after intravitreal conbercept injections

This study reports the short-term efficacy and safety of intravitreal conbercept injections for neovascularization at the disc (NVD) in patients with proliferative diabetic retinopathy (PDR). Conbercept is a recombinant fusion protein with a high affinity for all isoforms of vascular endothelial growth factor (VEGF)-A, placental growth factor and VEGF-B. A prospective case series study was conducted in 15 patients (15 eyes). Patients had complete ocular examinations and received a 0.5 mg intravitreal conbercept injection followed by supplemental pan-retinal photocoagulation (PRP). Optical coherence tomography angiography (OCTA) was performed before and after treatment. Before treatment, the mean NVD area was 1.05 ± 0.33 mm², and it decreased to 0.56 ± 0.17 mm² after an interval of 7.5 d (p = 0.000). One eye required vitrectomy during follow-up. Recurrent NVD was observed in 2 eyes, which resolved after repeated injections. The remaining 12 eyes were stable over a mean follow-up period of 8.3 months. The mean area of the NVD in 14 patients without vitrectomy was 0.22 ± 0.11 mm² (p = 0.000) at the last visit. Intravitreal conbercept injections combined with intensive PRP are an effective and safe treatment for PDR with NVD. Quantitative information on NVD can be obtained with OCTA, which may be clinically useful in evaluating the therapeutic effect.

Targeting endothelial metaflammation to counteract diabesity cardiovascular risk: Current and perspective therapeutic options

The association of obesity and diabetes, termed "diabesity", defines a combination of primarily metabolic disorders with insulin resistance as the underlying common pathophysiology. Cardiovascular disorders associated with diabesity represent the leading cause of morbidity and mortality in the Western world. This makes diabesity, with its rising impacts on both health and economics, one of the most challenging biomedical and social threats of present century. The emerging comprehension of the genes whose alteration confers inter-individual differences on risk factors for diabetes or obesity, together with the potential role of genetically determined variants on mechanisms controlling responsiveness, effectiveness and safety of anti-diabetic therapy underlines the need of additional knowledge on molecular mechanisms involved in the pathophysiology of diabesity. Endothelial cell dysfunction, resulting from the unbalanced production of endothelial-derived vascular mediators, is known to be present at the earliest stages of insulin resistance and obesity, and may precede the clinical diagnosis of diabetes by several years. Once considered as a mere consequence of metabolic abnormalities, it is now clear that endothelial dysfunctional activity may play a pivotal role in the progression of diabesity. In the vicious circle where vascular defects and metabolic disturbances worsen and reinforce each other, a low-grade, chronic, and 'cold' inflammation (metaflammation) has been suggested to serve as the pathophysiological link that binds endothelial and metabolic dysfunctions. In this paradigm, it is important to consider how traditional antidiabetic treatments (specifically addressing metabolic dysregulation) may directly impact on inflammatory processes or cardiovascular function. Indeed, not all drugs currently available to treat diabetes possess the same anti-inflammatory potential, or target endothelial cell function equally. Perspective strategies pointing at reducing metaflammation or directly addressing endothelial dysfunction may disclose beneficial consequences on metabolic regulation. This review focuses on existing and potential new approaches ameliorating endothelial dysfunction and vascular inflammation in the context of diabesity.

Overexpression of uncoupling protein 2 inhibits the high glucose-induced apoptosis of human umbilical vein endothelial cells

Ectopic apoptosis of vascular cells plays a critical role in the early stage development of diabetic retinopathy (DR). Uncoupling protein 2 (UCP2) is a mitochondrial modulator which protects against endothelial dysfunction. However, the role which UCP2 plays in endothelial apoptosis and its association with DR was unclear. In the present study, we investigated whether UCP2 functioned as an inhibitor of DR in endothelial cells. Firstly, we noted that in UCP2-knockout mice retinal cell death and damage in vivo was similar to that of db/db diabetic mice. Additionally, UCP2 knockdown induced caspase-3 activation and exaggerated high glucose (HG)-induced apoptosis of human umbilical vein endothelial cells (HUVECs). Conversely, adenovirus-mediated UCP2 overexpression inhibited the apoptosis of HUVECs and HG-induced caspase-3 activation. Furthermore, HG treatment resulted in the opening of the permeability transition pore (PTP) and liberation of cytochrome c from mitochondria to the cytosol in HUVECs. Notably, UCP2 overexpression inhibited these processes. Furthermore, adenovirus-mediated UCP2 overexpression led to a significant increase in intracellular nitric oxide (NO) levels and a decrease in reactive oxygen species (ROS) generation in HUVECs. Collectively, these data suggest that UCP2 plays an anti-apoptotic role in endothelial cells. Thus, we suggest that approaches which augment UCP2 expression in vascular endothelial cells aid in preventing the early stage development and progression of DR.

Advances in diabetic retinopathy

Diabetic retinopathy (DR) is a complication of long-term diabetes mellitus (DM). Over the last 2 decades lot of work has been on early diagnosis of DR and screening programs have been designed to help the masses. Large numbers of clinical studies have been done for patients of diabetes and DR wherein the role of blood sugar control, metabolic control, role of oral medicines for DR, role of imaging, fluorescein angiography, and retinal photocoagulation has been studied. Newer treatment modalities are being devised and studied for better patient care. We discuss these issues in our review highlight and newer advances over the last few years.

Bevacizumab treatment reduces retinal neovascularization in a mouse model of retinopathy of prematurity

AIM

To evaluate the effect of different bevacizumab concentrations on retinal neovascularization in a retinopathy of prematurity (ROP) mouse model.

METHODS

A total of 60 of C57BL/6 J mice were exposed to 75%±2% oxygen from postnatal d7 to postnatal d12. Fifteen nonexposed mice served as negative controls (group A). On d12, 30 mice (group C) were injected with 2.5 µg intravitreal bevacizumab (IVB), 30 mice (group D) were injected with 1.25 µg IVB in one eye. The contralateral eyes were injected with balanced salt solution (BSS) (control group=group B). The adenosine diphosphatase (ADPase) histochemical technique was used for retinal flat mount to assess the oxygen-induced changes of retinal vessels. Neovascularization was quantified by counting the endothelial cell proliferation on the vitreal side of the inner limiting membrane of the retina. Histological changes were examined by light microscopy. The mRNA levels of vascular endothelial growth factor (VEGF) were quantified by Real-time PCR. Western-blotting analysis was performed to examine the expression of P-VEGFR.

RESULTS

Comparing with the control group B, regular distributions and reduced tortuosity of vessels were observed in our retinal flat mounts in groups C and D. The endothelial cell count per histological section was lower in groups C (P<0.0001) and D (P<0.0001) compared with the control group B. Histological evaluation showed no retinal toxicity in any group. In all oxygen treated groups VEGF mRNA expression was significantly increased as compared to age-matched controls. No significant change in VEGF mRNA expression could be achieved in either of the treatments or the oxygen controls. The results of the Western blot were consistent with that of the Real-time PCR analysis.

CONCLUSION

An intravitreal injection of Bevacizumab is able to reduce angioproliferative retinopathy in a mouse model for oxygen-induced retinopathy.

Experimental histopathological study on retinal and renal cellular response to intravitreous antiangiogenic drugs

AIM

To evaluate histopathological retinal and renal response after one single dose of intravitreous injection of antiangiogenic drugs ranibizumab and bevacizumab in rats.

METHODS

Experimental study in 60d of life adults Wistar rats. Ten animals were included. Group 1 included 5 animals that were injected with 1 µL ranibizumab 1.25 mg in the right eye and with 1 µL of balanced salt solution (BSS) in the left eye, as control; Group 2 included 5 animals that were injected with 1 µL of bevacizumab in the right eye and with 1 µL of BSS in the fellow eye. All injections were performed with Hamilton syringes. After 15d of the interventions, all animals were sacrificed in CO2 chamber. Both eyes were enucleated and one kidney was removed, fixed and embedded in paraffin for histopathological analysis by optic microscopy. For statistical purposes the initial expected abnormal histopathological responses were defined as 0%.

RESULTS

Atypical histopathological retinal response was detected in 2 eyes injected with ranibizumab (40%) as well as in 2 control eyes in group 1. Same was detected in 1 eye injected with bevacizumab (20%) as well as in 1 control eye, in group 2. The noted atypical findings were lymphocytes and eosinophils in the vitreous posterior cavity and mild retinal inflammatory reaction with ganglion cell layer edema but without clinical significance. No atypical histopathological renal response was detected.

CONCLUSION

Unexpected atypical histopathological retinal response without clinical significance was observed in 3 eyes injected with antiangiogenic drugs (2 in group 1 and 1 in group 2) as well as in 3 control eyes (2 in group 1 and 1 in group 2). No atypical renal response was detected suggesting no extra ocular involvement of the intravitreous injected antiangiogenic drugs.