To understand why this matters, it helps to grasp how HIF works at the molecular level. The factor is a heterodimer composed of an oxygen-sensitive alpha subunit and a constitutive beta subunit. In well-oxygenated cells, prolyl hydroxylase enzymes tag the alpha subunit with hydroxyl groups, marking it for recognition by the von Hippel-Lindau tumor suppressor protein, which ubiquitinates HIF-alpha and condemns it to rapid destruction by the proteasome. When oxygen levels fall, this degradation machinery stalls. HIF-alpha accumulates, translocates to the nucleus, and pairs with HIF-beta to bind hypoxia response elements scattered throughout the genome. The result is a coordinated transcriptional surge: genes encoding vascular endothelial growth factor, erythropoietin, glycolytic enzymes, matrix metalloproteinases, and dozens of other survival and angiogenic proteins are switched on simultaneously. In the retina, a tissue with one of the highest metabolic oxygen demands in the body, this ancient oxygen-sensing system becomes a double-edged sword.

The review systematically dissects how this switch malfunctions in the three leading causes of vision loss. In diabetic retinopathy, chronic hyperglycemia does more than starve retinal tissue of oxygen through capillary dropout; it also stabilizes HIF-alpha directly through oxidative stress and inflammatory pathways, even in relatively well-oxygenated regions. In retinopathy of prematurity, the premature infant’s retina, still developing its vascular supply in a hyperoxic incubator environment, undergoes vaso-obliteration followed by a hypoxic phase in which HIF-driven VEGF floods the tissue and spawns disorganized, leaky vessels that can detach the retina. In neovascular age-related macular degeneration, the choroidal vasculature beneath the macula invades the retinal pigment epithelium in response to a hypoxic, inflamed, and drusen-laden microenvironment, with HIF orchestrating the choroidal neovascular membranes that hemorrhage and scar. In each disease, the authors emphasize, HIF integrates diverse upstream insults into a common downstream effector network.

Herein lies the problem with anti-VEGF therapy, the current standard of care. Drugs such as ranibizumab, aflibercept, and bevacizumab neutralize a single growth factor, and they transformed outcomes when introduced, saving the sight of millions. Yet a substantial fraction of patients respond inadequately or lose efficacy over time, a phenomenon the review frames as a structural limitation rather than a pharmacological accident. Because VEGF is only one branch of the HIF-dependent program, blocking it leaves the master switch intact and free to compensate through alternative angiogenic pathways, including placental growth factor, angiopoietins, hepatocyte growth factor, and inflammatory cytokines. Resistance emerges not because the drug fails to bind its target but because the upstream transcriptional engine keeps running, producing ever more redundant signals. Titrating the conductor, the authors argue, is more rational than silencing a single instrument in the orchestra.

The translational centerpiece of the review is its survey of HIF-targeted drug candidates, with particular attention to two lead compounds: 32-134D and PX-478. Both are small-molecule inhibitors designed to suppress HIF-alpha accumulation or activity, and both have progressed through preclinical evaluation with encouraging ocular data. By damping the master switch itself, these agents promise broader therapeutic coverage than any single-ligand blockade, potentially addressing leakage, neovascular proliferation, and fibrotic remodeling in one stroke. The authors also survey strategies at the molecular level, including approaches that modulate prolyl hydroxylase activity, disrupt HIF dimerization, or interfere with co-activator recruitment, as well as emerging delivery platforms suited to the eye’s immune-privileged and anatomically constrained environment. The review frames these efforts as a pipeline moving from bench chemistry toward clinical validation, though it is careful to note that no HIF inhibitor has yet replaced anti-VEGF injection in routine retinal practice.

Perhaps the most scientifically nuanced section of the review concerns HIF’s dual identity. The same transcription factor that fuels pathological vessel growth is indispensable for physiological vascular development. Embryonic retinal vessels form under HIF guidance; the ordered sprouting, tip-cell migration, and anastomosis that build a functional capillary network depend on precisely calibrated HIF signaling. Complete, indiscriminate suppression of the pathway risks impairing wound healing, neuroprotection, and normal vascular maintenance, particularly in premature infants whose retinas are still under construction. The authors stress that therapeutic success will hinge on precision in three dimensions: timing, so that treatment is delivered when pathological signaling dominates; cell type, so that pathogenic stabilization of HIF in endothelial cells, pericytes, or retinal pigment epithelial cells is targeted without disabling protective programs elsewhere; and microenvironment, so that the specific mix of hypoxic, metabolic, and inflammatory cues driving disease in each patient is taken into account.

This framing carries real clinical weight for the millions of people affected by these conditions. Diabetic retinopathy remains a leading cause of blindness in working-age adults as global diabetes prevalence climbs; neovascular age-related macular degeneration threatens an aging population in which patients face years of monthly or bimonthly intravitreal injections and a meaningful minority derive limited benefit; and retinopathy of prematurity grows more relevant as neonatal intensive care expands in low- and middle-income countries. A therapy that acts upstream could, in principle, reduce injection frequency, overcome tachyphylaxis, and address the fibrotic late stages that anti-VEGF drugs handle poorly. The review’s synthesis suggests that the field’s long-standing focus on VEGF, while enormously productive, may have been a necessary but incomplete first act.

The authors are equally candid about limitations. HIF biology is pleiotropic: the factor regulates metabolism, erythropoiesis, cell survival, and immune function throughout the body, raising concerns about systemic toxicity if inhibitors escape the eye. Pharmacokinetics in the vitreous, the optimal molecular target within the HIF pathway, and the risk of interfering with physiological repair processes all remain open questions. Clinical evidence for compounds like 32-134D and PX-478 in ocular disease is still maturing, and the review explicitly calls for further work to define which patients, which disease stages, and which combinations with existing anti-VEGF agents will maximize benefit. The dual role of HIF means that the therapeutic window, while real, must be mapped with care rather than assumed.

What emerges from the review is less a single breakthrough than a reframing of the problem. Ocular neovascularization, in this account, is not a VEGF excess disease but a transcriptional state disease, in which a master oxygen sensor is locked in the on position by hypoxia, hyperglycemia, oxidative stress, and inflammation. Anti-VEGF therapy treats the loudest symptom; HIF-targeted strategies aim at the control circuit itself. If the lead candidates now moving through translational pipelines can deliver broad efficacy with an acceptable safety profile and the precision of timing, cell type, and microenvironment that the authors demand, the standard of care for blinding retinal disease could shift from repeated downstream blockade to durable upstream control. For patients facing a lifetime of injections or the prospect of irreversible vision loss, that would represent one of the most consequential advances in ophthalmology in a generation.

Subject of Research: The role of hypoxia-inducible factor in ocular neovascularization and HIF-targeted strategies to overcome anti-VEGF resistance

Article Title: Hypoxia-inducible factor as a master switch in ocular neovascularization: overcoming anti-VEGF resistance and exploring therapeutic prospects

Article References: Liu, T., He, Y.-F., Liao, Y.-F., Wu, X.-J., Zhang, Y.-P., Li, J., Liu, J.-X., Wang, T., Wu, Z.-X., & You, Z.-P. (2026). Hypoxia-inducible factor as a master switch in ocular neovascularization: overcoming anti-VEGF resistance and exploring therapeutic prospects. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08976-4

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08976-4

Keywords: hypoxia-inducible factor, ocular neovascularization, anti-VEGF resistance, diabetic retinopathy, retinopathy of prematurity, age-related macular degeneration, angiogenesis, HIF inhibitors, 32-134D, PX-478, vascular leakage, translational medicine

Writing in the journal New Microbes and New Infections, a team led by researchers at the CSIR Institute of Genomics and Integrative Biology and Max Hospital in New Delhi reports a whole-blood transcriptomic analysis of 112 dengue-positive patients recruited at their first hospital visit. The participants were classified according to the revised 2009 WHO guidelines into those without warning signs and those with warning signs, the latter defined by coagulation abnormalities such as thrombocytopenia, clinical fluid accumulation reflected in hemoconcentration, and increased vascular fragility. Within the group without warning signs, 46 patients also presented with leukopenia, allowing the investigators to stratify the cohort into mild, moderate and relatively severe subgroups. Although none of the patients met the formal criteria for severe dengue, the 21 patients carrying warning signs together with thrombocytopenia were treated as demonstrating a propensity for clinically severe outcomes because of their depressed platelet counts.

The technical pipeline behind the study was considerable. The team isolated RNA from one milliliter of whole blood per patient, depleted globin and ribosomal RNA, and generated stranded sequencing libraries that were run as paired-end 151-base-pair reads on an Illumina NextSeq 2000 platform. The effort produced more than two billion reads, averaging about 18.5 million reads per sample. After quality trimming and quasi-mapping to the human transcriptome, differential expression was computed with DESeq2, and confounder analyses for age and sex showed no significant differences between the clinical groups. All 112 patients experienced primary dengue infection, and serotype analysis based on viral reads recovered from the sequencing data indicated that the majority were infected with DENV-2, consistent with the serotype circulating in Delhi during the study period. Samples were collected during the acute febrile phase, with a mean of 3.69 days of fever at enrollment.

The clinical chemistry told a coherent story before any sequencing was considered. Total leukocyte counts, platelets, lymphocytes and neutrophils all differed significantly between the groups, with p-values below 0.001. The two leukopenic groups showed lower neutrophil and higher lymphocyte values than the mild group, a pattern the authors interpret as a subdued first-line defense, since neutrophils are the earliest active killers of pathogens during viral and bacterial infections. Notably, hematocrit was not elevated in the patients with warning signs, suggesting that capillary leak had not yet begun at the time of sampling. Liver function tests available for a subset of patients showed higher SGOT and SGPT values in the warning-sign group, along with significantly lower total protein and elevated bilirubin, although all values remained within normal ranges, hinting at hepatic derangement that was only beginning to emerge.

Differential expression analysis between the moderate and mild groups yielded 15 significantly downregulated genes, most of them involved in immune response and inflammation, including the chemokine CXCL2, the neutrophil marker CD177, the acute-phase protein ORM1 and the inflammation regulator PI3. The authors read this as evidence of a subdued immune response in moderate patients compared with mild ones. By contrast, comparisons involving the severe group were far more dramatic: severe versus mild produced 215 upregulated and 92 downregulated genes, while severe versus moderate produced 142 upregulated and only 2 downregulated genes. Pathway enrichment against the Reactome database showed that upregulated functions in severe patients centered on glycosylation and the nervous system, whereas downregulated pathways encompassed immune and inflammatory response, GPCR signaling, platelet activation and aggregation, and prostaglandin synthesis in platelets and endothelial cells.

One of the most intriguing findings was that, although many immune response genes were downregulated in severe patients, a diverse repertoire of B cell receptor genes, including immunoglobulin light and heavy chain variables, was upregulated, indicating an acute antibody response associated with severity. Upregulation of KIR3DL3, LILRB5 and IRAK1BP1 appeared to divert innate immune pathways toward resolution of inflammation. Taken together, the differential expression profile suggests an attenuation of immune and inflammatory activity in severe patients precisely at the time when platelet counts fall below normal thresholds due to platelet dysfunction, a counterintuitive pattern that complicates the traditional picture of dengue severity as a cytokine-driven hyperinflammatory state.

To move beyond lists of individual genes, the team applied Weighted Gene Co-expression Network Analysis, or WGCNA, to 14,071 genes across all 112 samples. After selecting an optimal soft-threshold power to ensure scale-free network topology, the algorithm organized the genes into 22 modules, each representing a set of genes with highly similar expression patterns. The severe subgroup split into two major clades with starkly different co-expression patterns: clade 1 modules showed higher expression in severe patients and were enriched for metabolism, glycosylation, nervous system processes and DNA repair, while clade 2 modules showed decreased expression and carried functions related to blood coagulation, platelet activation, cell adhesion, immune response, regulation of virus replication, interferon response and cytokine signaling. Correlating module eigengenes with clinical parameters revealed that clade 2 modules correlated positively with platelet counts, while a single module, turquoise, correlated negatively, reinforcing the link between immune response modules and platelet dysregulation. Total leukocyte count, by contrast, showed no significant correlation with any module.

Within the platelet-associated modules, the investigators identified a set of genes that collectively define the severe state. The greenyellow module contained interferon pathway genes such as IFI44L, IFI35, OAS1, SAMD9L and KAT2B, while the darkred module harbored genes governing platelet function, coagulation and endothelial integrity, including ARHGEF12, CTTN, SELP, PPBP, PRKAR2B and F13A1. Other modules captured vesicular trafficking genes such as GOLGA7 and RAB27B, thought to be required for viral replication and autophagy, and innate antiviral genes including IFIH1, which encodes the cytosolic RNA sensor MDA5, and HNRNPA2B1. When the team dichotomized the severe patients by platelet count, comparing those below 100 times 10 to the ninth per liter with those between 100 and 140, 16 genes showed significant differences in baseline transcript abundance, with IFI44L standing out at a difference of more than 800 counts per million. Regression analysis found no genes significantly correlated with SGOT, implying that modest transaminase elevations do not substantially shape disease outcome.

The findings converge with transcriptomic studies of dengue patients in Brazil, where interferon-stimulated genes such as IFI27 and ISG15 emerged as biomarkers capable of distinguishing dengue hemorrhagic fever from uncomplicated dengue during the late acute phase. Although IFI27 was not captured in the Indian dataset, ISG15 was consistently upregulated in patients with warning signs and low platelets, aligning with its proposed role as a severity marker. The Indian study also detected CTTN, a gene tied to endothelial barrier function that was not a focus of the Brazilian datasets, hinting at population-specific elements of the immune-endothelial axis. The authors propose a sequential pathogenic cascade for patients with warning signs: a suboptimal early interferon and innate immune response weakens host defenses and permits viral replication, heightened viral stress drives platelet dysfunction and clearance, and, independently of cytokine-mediated hyperinflammation, upregulation of O-linked glycosylation genes such as GALNT13, B4GALT1 and B3GNT4 alongside downregulation of structural genes like CTTN alters the endothelial glycocalyx, producing the vascular permeability that characterizes the onset of clinical warning signs.

The study carries the inherent limitation of a cross-sectional design, since blood was drawn at a single acute-phase time point, and whole-blood RNA means the observed signatures may partly reflect shifts in circulating cell composition rather than purely transcriptional changes within individual cell types. The authors note that single-cell transcriptomics or computational deconvolution in future longitudinal cohorts would help resolve cell-type-specific contributions. Even so, the work suggests practical avenues: monitoring glycocalyx-related gene signatures could enable early identification of patients at risk of severe disease, and therapeutic strategies aimed at preserving glycocalyx integrity may offer a novel way to reduce vascular complications. If validated across larger and more geographically diverse cohorts, the interferon and glycosylation signatures identified here could become molecular biomarkers for predicting, and perhaps mitigating, severe dengue before the first warning signs appear.

Subject of Research: Host transcriptomic signatures associated with severe dengue infection in Indian patients

Article Title: Interferon gamma and inflammatory response genes by weighted gene co-expression network analysis reveal significant associations with severe dengue infection in India

Article References: Shamim, U., Arora, S., Maurya, R., Soni, J., Shukla, R., Mehta, P., Tarai, B., Budhiraja, S., & Pandey, R. (2026). Interferon gamma and inflammatory response genes by weighted gene co-expression network analysis reveal significant associations with severe dengue infection in India. New Microbes and New Infections, 74, Article 101855. https://doi.org/10.1016/j.nmni.2026.101855

Image Credits: AI Generated

DOI: 10.1016/j.nmni.2026.101855

Keywords: dengue, DENV-2, interferon, WGCNA, transcriptomics, thrombocytopenia, endothelial glycocalyx, glycosylation, innate immunity, biomarkers, India, vascular leakage

The new analysis, led by Kai-Yang Chen of Chang Gung Memorial Hospital in Taiwan, together with Hoi-Chun Chan of China Medical University and Chi-Ming Chan of Cardinal Tien Hospital and Fu Jen Catholic University, was prospectively registered with PROSPERO and conducted according to the PRISMA 2020 reporting guidelines. The team searched PubMed, Scopus, Web of Science, ScienceDirect, and the Cochrane Library from inception through April 21, 2026, screening more than 1,200 records to identify 25 eligible studies spanning in vitro experiments, animal models, and early- to late-phase human trials.

The biological rationale is compelling. Diabetic retinopathy alone affects approximately 22 percent of people with diabetes, roughly 103 million adults as of 2020, and is projected to reach 160 million by 2045. Neovascular age-related macular degeneration shares a common final pathway: VEGF-driven pathological angiogenesis and breakdown of the blood-retinal barrier, producing macular edema, capillary nonperfusion, and progressive retinal damage. Current anti-VEGF injections suppress these processes only transiently, requiring repeated administration and carrying procedural risks including endophthalmitis, elevated intraocular pressure, and cataract. Gene therapy, typically delivered via adeno-associated viral (AAV) vectors, aims to turn the eye itself into a factory for therapeutic proteins, achieving sustained pathway-level disease control after a single procedure.

The preclinical results are striking. Across eight animal and in vitro studies, gene therapy significantly reduced pathological neovascularization, with a pooled standardized mean difference of −1.16 (95 percent confidence interval, −1.48 to −0.84; p < 0.001), meaning the reduction exceeded one full standard deviation compared with controls. Remarkably, heterogeneity was negligible, with an I² of 0 percent, indicating extraordinary consistency despite differences in vector platforms, transgenes, and disease models. Within the oxygen-induced retinopathy subgroup, the effect was even larger, with a standardized mean difference of approximately −1.29, reflecting robust suppression of ischemia-driven retinal angiogenesis by constructs including soluble VEGF receptor sFLT-1, pigment epithelium-derived factor (PEDF), angiostatin, and the antioxidant enzyme MnSOD.

Vascular leakage, the other hallmark of these diseases, was also significantly reduced. Three preclinical experimental studies using AAV- and adenovirus-mediated gene transfer showed a pooled mean difference of 0.215 on a directionally harmonized scale (95 percent CI, 0.178 to 0.251; p < 0.001), again with zero heterogeneity. Complementary mechanistic work showed that sFLT-1 expression reduced VEGF-induced endothelial permeability by roughly 40 to 60 percent while preserving tight junction proteins, and antioxidant gene transfer reduced oxidative stress-driven barrier breakdown. In vivo, fluorescein leakage scores fell by 30 to 70 percent following anti-VEGF or PEDF gene delivery, while antioxidant therapy reduced acellular capillaries by approximately 40 to 60 percent, indicating preservation of the retinal microvasculature beyond angiogenesis alone.

The clinical evidence, though still early-stage, points in the same direction. Across eight clinical cohorts, ocular gene therapy produced a statistically significant reduction in central subfield thickness of −55.30 micrometers (95 percent CI, −72.58 to −38.03; p < 0.001), a meaningful anatomical improvement reflecting reduced macular edema and fluid accumulation. In the phase 1 trial of intravitreal AAV2-sFLT01 reported by Heier and colleagues, individual eyes showed central thickness reductions of up to roughly 600 micrometers at week 18 and 860 micrometers by week 52, while the phase 2a trial of subretinal rAAV.sFLT-1 by Constable and colleagues demonstrated stabilization of retinal thickness over 52 weeks.

Perhaps the most clinically consequential finding concerns treatment burden. Across seven clinical cohorts, the pooled logit event rate of 0.62 (95 percent CI, 0.20 to 1.04; p = 0.0039) corresponds to approximately 65 percent of participants meeting study-specific criteria for reduced supplemental anti-VEGF injections after gene therapy. Heterogeneity was low, at roughly 11 percent, despite differences between AAV and lentiviral platforms, delivery routes, and dosing regimens. This outcome directly addresses the central weakness of current standard care: the cumulative burden and adherence challenges of repeated intravitreal injections.

The analysis also situates these findings within a rapidly advancing clinical pipeline. Next-generation programs including ABBV-RGX-314, ADVM-022 (ixo-vec), and 4D-150 have progressed into phase II/III trials for neovascular retinal diseases, with early data showing reductions in anti-VEGF injection burden of up to 80 to 97 percent alongside stable visual and anatomical outcomes. Notably, 4D-150 employs dual inhibition of VEGF-A and VEGF-C, an evolution beyond earlier single-target constructs, while ADVM-022 offers intravitreal delivery that avoids surgery, and RGX-314 has shown durability across both subretinal and suprachoroidal routes. The concordance between these emerging results and the meta-analysis findings reinforces the biological validity of sustained intraocular VEGF suppression.

The authors are careful to acknowledge limitations. Some functional outcomes were drawn from trials of non-angiogenic inherited retinal disorders, including Leber hereditary optic neuropathy, RPE65-associated Leber congenital amaurosis, and X-linked retinitis pigmentosa, and were interpreted as proof of concept for gene delivery and durability rather than anti-angiogenic efficacy. The XIRIUS phase 2/3 trial of cotoretigene toliparvovec in X-linked retinitis pigmentosa, for example, missed its primary endpoint, underscoring the importance of disease context, dose selection, and intervention timing. Animal models, meanwhile, do not fully reproduce the chronic metabolic milieu of human diabetic retinopathy. Publication bias analyses were largely reassuring, though small-study effects were flagged for central subfield thickness and injection burden outcomes, and trim-and-fill sensitivity analyses supported the robustness of the primary estimates.

Safety data across translational stages suggest an acceptable early profile, with adverse events largely procedure-related or reflecting transient ocular inflammation. However, the authors caution that limited sample sizes, heterogeneous reporting, and incomplete long-term follow-up constrain safety conclusions, particularly given the potential irreversibility of ocular gene transfer. The path forward, they argue, requires adequately powered, disease-specific randomized trials, standardized outcome definitions, harmonized optical coherence tomography metrics, and long-term surveillance of transgene durability and immunogenicity. If those trials confirm the signals synthesized here, ocular gene therapy could shift the treatment of neovascular retinal disease from a lifetime of monthly injections toward long-acting or single-administration therapy, fundamentally changing the outlook for the hundreds of millions at risk of preventable vision loss worldwide.

Subject of Research: Ocular gene therapy targeting retinal angiogenesis and vascular leakage in neovascular retinal diseases

Article Title: Ocular gene therapy targeting retinal angiogenesis and vascular leakage: translational and clinical evidence from a systematic review and meta-analysis

Article References: Ocular gene therapy targeting retinal angiogenesis and vascular leakage: translational and clinical evidence from a systematic review and meta-analysis. (n.d.). https://doi.org/10.1007/s10456-026-10050-y

Image Credits: AI Generated

DOI: 10.1007/s10456-026-10050-y

Keywords: ocular gene therapy, retinal angiogenesis, vascular leakage, anti-VEGF, adeno-associated virus, neovascular age-related macular degeneration, diabetic retinopathy, systematic review, meta-analysis, sFLT-1, central subfield thickness, retinal disease