Recently, researchers announced that they have found a new target for inhibiting vascular endothelial growth factor (VEGF), which can improve the symptoms of ophthalmic diseases. This is achieved by affecting the release of VEGF and choroidal neovascularization through fat mass and obesity-associated protein (FTO) inhibition. These findings provide a new research mechanism for ophthalmic treatment. The relevant research results were published in the February 2023 issue of "Signal Transduction and Targeted Therapy", a sub-journal of "Nature".

VEGF is a group of important regulatory factors that can stimulate the growth of new blood vessels (angiogenesis) and increase the permeability of existing blood vessels. It plays a critical role in normal development and wound healing. VEGF includes several types, such as VEGFA, VEGFB, VEGFC, VEGFD, VEGFE, and PLGF. In drug research, VEGFA is the most common type, and it is involved in endothelial cell proliferation, migration, and microvascular formation. When VEGFA is overexpressed in the eye, it can cause abnormal blood vessel proliferation, vascular leakage, and other ophthalmic diseases, such as macular degeneration, diabetic retinopathy, corneal neovascularization, and so on.

1. Research Progress of VEGF-targeted Drugs

So far, multiple VEGF drugs have been approved for the treatment of macular degeneration, tumors, and other vascular-related diseases. From the research and development perspective, the main focus is on two areas: ophthalmic diseases and tumors.

The application of VEGF drugs in ophthalmology is mainly targeted at some macular-related diseases, such as wet age-related macular degeneration and diabetic retinopathy. The common feature of these diseases is the neovascularization and leakage of capillaries in the macular region, leading to retinal edema and vision loss. VEGF is one of the important factors causing abnormal blood vessel generation. Therefore, the use of VEGF drugs can inhibit abnormal blood vessel generation, reduce leakage, and improve patients' vision and ophthalmic symptoms.

Common VEGF targeted drugs used for ophthalmic diseases include aflibercept, conbercept, bevacizumab, and ranibizumab. In addition, many VEGF drugs are currently undergoing clinical trials. According to data from ClinicalTrials, there are more than 600 clinical trials related to these drugs.

2. Phenotypically Stable Humanized VEGFA Mice

To better investigate the pathological mechanisms of ophthalmic diseases and help develop targeted drugs, Cyagen has established a model of human VEGFA gene CDS sequence expression driven by a rod cell-specific promoter in C57BL/6J mice, to obtain transgenic mice that overexpress the human VEGFA gene specifically in the retina. This humanized VEGFA (hVEGFA) overexpression mouse model can develop spontaneous vascular lesions on the intact eye structure, which can be used for drug evaluation and related mechanism research of neovascular-related ophthalmic diseases. In addition, using their self-developed hVEGFA mice, Cyagen has conducted positive drug tests, such as aflibercept and bevacizumab, to evaluate the inhibitory effects of targeting hVEGFA.

          Figure 1. The construction method of hVEGFA mice.

Cyagen's ophthalmic CRO platform has a team of ophthalmic experts trained to perform experimental operation with our sophisticated instruments and equipment. We can perform in vivo ophthalmic detection techniques for hVEGFA mouse models, including eye surface observation, intraocular pressure measurement, fundus photography, image-guided optical coherence tomography (OCT), full-field electroretinogram (ERG), and fundus fluorescein angiography (FFA), optokinetic response (OKR), and more. At the same time, they have professional pathology and molecular detection techniques, including evaluation of retinal hVEGFA expression levels, FITC-Dextran perfusion retinal flat mount, and hVEGFA expression levels in eye tissue sections to evaluate vascular lesions.

3. Humanized VEGFA Mouse Model Verification Case Study

According to the experimental verification by the Cyagen technical team, the F0 generation of hVEGFA mice showed significant, clear, and stable fluorescent leakage spots in the fundus, similar to the phenotype of neovascular age-related macular degeneration. The F1 and F2 generations of mice can stably inherit the parental phenotype, making them suitable for preclinical studies such as VEGFA drug efficacy evaluation.

FFA (Fundus fluorescein angiography) results showed that there were vascular lesions in the mouse fundus and widespread leakage of fluorescein sodium.

                                                  Figure 2. Fundus fluorescein angiography results of hVEGFA mice (F0).

OCT showed mild disruption in the choroidal region.

Figure 3. OCT results of hVEGFA mice (F0).

ERG showed no significant difference in retinal potentials compared to WT mice.


Figure 4. ERG results of hVEGFA mice (F0).

FFA (Fundus fluorescein angiography) results showed that F1 mice were able to reproduce the F0 phenotype.

Figure 5. Fundus fluorescein angiography results of hVEGFA mice (F1).

FFA (Fundus fluorescein angiography) results showed that F2 mice were able to reproduce the F0 and F1 phenotypes.

Figure 6. Fundus fluorescein angiography results of hVEGFA mice (F2).

Any anti-VEGF (human VEGF) AAVs and/or AAVs that can eventually carry therapeutic proteins can be tested well with the hVEGFA transgenic mice. The rod cells in the eyes of hVEGFA mice will specifically overexpress Humanized VEGFA protein and mice develop wAMD phenotype, which is stably inherited through F2 generation. For these reasons, hVEGFA mice are one of the best wAMD models to test for therapeutic antibodies and/or fusion proteins (e.g. small drugs, protein-based drugs, AAVs that can eventually carry therapeutic proteins). Cyagen's AI-AAV discovery platform can assist with your vector design and development needs.

4. Other Established Eye Disease Models

In addition to the hVEGFA mouse model mentioned above, Cyagen has also developed a series of gene-edited and humanized mouse models for diseases such as retinitis pigmentosa, congenital amaurosis, and achromatopsia. Cyagen also provides personalized custom services for researchers.

Disease    Target Gene Gene Targeting Type
Macular degeneration hVEGFA KI、TG
ABCA4(ABCR) KO、Humanization
Pigmentary degeneration of retina RHO KO、CKO、Humanization、Humanization(Mu)
Mertk KO、CKO
Rpgr KO
Crb1 KO
Rd1(Pde6b) KO、MU
Rd10(Pde6b) MU
Retinal degeneration Tub KO
Late-Onset Retinal Degeneration Rds(Prph2) KO
Leber congenital amaurosis type 2 Rpe65 KO、MU
Leber congenital amaurosis type 4 Aipl1 KO
Leber congenital amaurosis type 10 CEP290 Humanization
Leber congenital amaurosis type 13 Rdh12 KO
Achromatopsia Cnga3 CKO
Fuchs endothelial dystrophy TCF4 CKO、Humanization
Congenital aniridia Pax6 CKO
Choroideremia  Chm CKO
Usher Syndrome USH2A Humanization
Myo7a CKO
Vitelliform macular degeneration Best1 KO
X-linked retinoschisis Rs1 KO、CKO
Oculocutaneous albinism type 1 Tyr CKO
Oculocutaneous albinism type 3 Tyrp1 KO、CKO
Wolfram Syndrome Wfs1 KO、CKO
Pseudoxanthoma elasticum Abcc6 KO、CKO