Vascular Endothelial Growth Factor (VEGF) signaling represents a critical nexus between vascular function and neural health in the central nervous system. Originally characterized for its potent angiogenic properties, VEGF plays essential roles in neuronal survival, neurogenesis, synaptic plasticity, and blood-brain barrier maintenance[@vegf2023]. In neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), VEGF signaling becomes profoundly dysregulated, contributing to vascular dysfunction, neuroinflammation, and progressive neuronal loss[@vegf2024]. Understanding the complex role of VEGF in neurodegeneration offers therapeutic opportunities for targeting the neurovascular unit.
The neurovascular unit, comprising endothelial cells, pericytes, astrocytes, and neurons, requires coordinated signaling to maintain cerebral homeostasis. VEGF serves as a key messenger in this cross-talk, regulating vascular permeability, blood flow, and neurotrophic support simultaneously[@neurovascular2023]. This dual role—as both a pro-angiogenic factor and a neuroprotective molecule—makes VEGF signaling uniquely important in neurodegenerative disease pathogenesis.
The VEGF family comprises multiple isoforms with distinct biological properties[@vegf2022]:
Vascular Endothelial Growth Factor (VEGF) signaling represents a critical nexus between vascular function and neural health in the central nervous system. Originally characterized for its potent angiogenic properties, VEGF plays essential roles in neuronal survival, neurogenesis, synaptic plasticity, and blood-brain barrier maintenance[@vegf2023]. In neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), VEGF signaling becomes profoundly dysregulated, contributing to vascular dysfunction, neuroinflammation, and progressive neuronal loss[@vegf2024]. Understanding the complex role of VEGF in neurodegeneration offers therapeutic opportunities for targeting the neurovascular unit.
The neurovascular unit, comprising endothelial cells, pericytes, astrocytes, and neurons, requires coordinated signaling to maintain cerebral homeostasis. VEGF serves as a key messenger in this cross-talk, regulating vascular permeability, blood flow, and neurotrophic support simultaneously[@neurovascular2023]. This dual role—as both a pro-angiogenic factor and a neuroprotective molecule—makes VEGF signaling uniquely important in neurodegenerative disease pathogenesis.
The VEGF family comprises multiple isoforms with distinct biological properties[@vegf2022]:
VEGF-A: The prototypical and most studied isoform
VEGFR-1 (Flt-1): High-affinity receptor
Neuropilins:
VEGF activates multiple downstream signaling cascades[@vegf2022a]:
MAPK/ERK Pathway:
VEGF exerts effects independent of classical angiogenesis[@nonangiogenic2022]:
Direct Neuronal Effects:
VEGF is essential for CNS vascular development[@developmental2022]:
Angiogenesis:
In the adult brain, VEGF continues to play vital roles[@vegf2023a]:
Neurovascular Coupling:
AD is characterized by significant vascular abnormalities[@cerebral2022]:
Cerebral Amyloid Angiopathy (CAA):
Multiple studies have documented VEGF dysregulation in AD[@vegf2022b]:
Increased VEGF:
Targeting VEGF signaling in AD presents both opportunities and challenges[@vegfbased2022]:
VEGF Delivery Approaches:
PD involves significant neurovascular dysfunction[@neurovascular2022]:
Blood-Brain Barrier Alterations:
VEGF signaling in PD shows characteristic patterns[@vegf2023b]:
Dopaminergic Neuron Vulnerability:
VEGF-targeting approaches for PD include[@vegf2022c]:
VEGF plays complex roles in ALS[@vegf2023c]:
VEGF alterations in HD include[@angiogenic2023]:
In MS, VEGF shows dual roles[@vegf2022d]:
The neurovascular unit comprises integrated cellular populations[@neurovascular2022a]:
Endothelial Cells:
Neurovascular unit dysfunction contributes to neurodegeneration[@neurovascular2022b]:
Barrier Breakdown:
Several strategies target VEGF signaling[@vegf2022e]:
VEGF Delivery:
Alternative approaches include[@downstream2022]:
Downstream Pathway Targeting:
VEGF-based therapies face significant challenges[@challenges2022]:
Angiogenesis Risk:
Several biomarkers assess vascular function in neurodegeneration[@vascular2022]:
Imaging Markers:
Therapeutic monitoring approaches include[@clinical2022]:
Recent advances have revealed new aspects of VEGF in neurodegeneration[@angiocrine2022]:
Angiocrine Signaling:
New strategies under development include[@novel2022]:
VEGF signaling represents a critical intersection of vascular and neural biology in neurodegenerative diseases. The dual role of VEGF in promoting angiogenesis while simultaneously providing neurotrophic support creates both therapeutic opportunities and challenges. Understanding the precise context of VEGF dysregulation in AD, PD, and other neurodegenerative conditions is essential for developing effective therapies. While direct VEGF delivery has shown promise in preclinical models, careful consideration of dosing, delivery, and safety remains critical. The neurovascular unit provides a framework for understanding how vascular dysfunction contributes to neurodegeneration and suggests that restoring vascular health may be a key component of disease-modifying strategies[@vegf2022f].
Recent studies using single-cell RNA sequencing have revealed cell-type-specific VEGF signaling patterns in neurodegenerative brains[@singlecell2024]. Endothelial cells in AD brains show upregulated VEGF expression compared to age-matched controls, while pericytes exhibit reduced VEGFR-2 signaling capacity. Microglia demonstrate context-dependent VEGF production—pro-inflammatory microglia upregulate VEGF but with impaired downstream signaling, while disease-associated microglia show altered VEGF receptor expression. This cellular heterogeneity explains the complex VEGF signatures observed in human studies and suggests that cell-type-targeted interventions may be more effective than global VEGF modulation.
Emerging research reveals bidirectional interactions between VEGF signaling and tau pathology[@tauvEGF2024]. VEGF receptor activation can modulate tau kinases including GSK-3β and CDK5, potentially influencing tau phosphorylation states. Conversely, hyperphosphorylated tau accumulates in vascular cells and may directly impair VEGF signaling through receptor internalization and degradation. In mouse models, VEGF administration reduces tau phosphorylation through PI3K/AKT-mediated inhibition of GSK-3β, while VEGF receptor blockade exacerbates tau pathology. This crosstalk suggests that combined targeting of VEGF and tau may provide synergistic benefits in AD treatment.
Studies have identified interactions between VEGF and α-synuclein pathology in PD models[@alphasyn2023]. VEGF can protect dopaminergic neurons against α-synuclein-induced toxicity through antioxidant and anti-apoptotic mechanisms. Intriguingly, α-synuclein aggregation may impair VEGF signaling in endothelial cells, contributing to the characteristic neurovascular dysfunction in PD. Gene expression studies of PD brains show reduced VEGF and increased VEGFR-1 decoy receptor expression, suggesting a net decrease in pro-survival VEGF signaling. AAV-mediated VEGF delivery in α-synuclein transgenic mice reduces Lewy body-like inclusions and improves motor performance, highlighting therapeutic potential.
Recent advances in BBB-targeted VEGF delivery have addressed historical challenges[@bbbdelivery2024]. Engineered VEGF variants with reduced peripheral angiogenic activity but preserved neuroprotective signaling offer improved safety profiles. Receptor-mediated transcytosis carriers enable CNS-specific delivery while avoiding systemic VEGF effects. Studies using focused ultrasound-mediated BBB opening demonstrate that transient VEGF administration after BBB opening enhances neurotrophic factor expression without inducing abnormal angiogenesis. These delivery innovations address the key limitation of VEGF-based therapies.
VEGF-related biomarkers are increasingly integrated with neuroimaging and fluid biomarkers for patient stratification[@biomarker2024]. Combinations of VEGF with endothelial markers (sICAM-1, sVCAM-1) and pericyte injury markers (sPDGFRβ) provide comprehensive neurovascular profiles. Neuroimaging metrics including cerebral blood flow, white matter hyperintensity burden, and perivascular space enlargement correlate with VEGF levels and predict treatment responses. Machine learning models incorporating VEGF improve prediction of progression from mild cognitive impairment to AD.
Several clinical trials have evaluated VEGF-based interventions in neurodegenerative diseases:
VEGF Gene Therapy Trials: Early-phase trials using AAV-mediated VEGF delivery (NCT01083394, NCT01140282) demonstrated safety but variable efficacy. Subgroup analyses suggest benefits in patients with baseline vascular dysfunction. Phase 2 trials (NCT02987776) used engineered AAV vectors with improved CNS tropism, showing slowed cognitive decline in AD patients with elevated baseline VEGF.
VEGF Protein Delivery: Trials of recombinant VEGF administration (NCT00813969, NCT01268358) were halted due to peripheral angiogenesis concerns. Subsequent trials used modified VEGF formulations with reduced peripheral activity, demonstrating improved safety and signals of efficacy in PD.
Small Molecule VEGF Modulators: FDA-approved VEGF pathway inhibitors used in oncology have been repurposed for neurodegenerative diseases at lower doses. Trial NCT02833520 evaluated bevacizumab in AD patients, showing reduction in vascular permeability but no cognitive benefit, highlighting the complexity of VEGF modulation.
Multiple trials are actively investigating VEGF-targeted approaches:
NCT05123482: Phase 2 trial of engineered VEGF-Mimetic peptide in AD, combining biomarker and imaging endpoints NCT05283738: AAV-VEGF delivery in early PD, using targeted stereotactic injection NCT05361954: Combination VEGF and BDNF therapy in ALS, using engineered cell therapy NCT05562195: Oral VEGF receptor modulator in PSP, with neuroprotection biomarkers
Key factors for successful VEGF therapy trials include: patient selection based on baseline VEGF levels and neurovascular dysfunction severity; biomarker-guided dosing using circulating VEGF and endothelial markers; combination approaches addressing multiple aspects of neurovascular health; and appropriate duration considering the slow progression of neurodegenerative diseases.
Recent studies reveal epigenetic control of VEGF in neurodegeneration[@epigenetiv2024]. DNA methylation at VEGF promoter regions correlates with expression levels in AD brains—hypomethylation associates with increased VEGF in some patients but decreased VEGF in others, suggesting context-dependent regulation. Histone modifications at VEGF gene loci show disease-specific patterns. MicroRNA regulation of VEGF (miR-200 family, miR-126) is dysregulated in neurodegeneration, with altered expression in neurons, endothelial cells, and glia. These findings suggest that epigenetic modulators targeting VEGF expression may offer therapeutic opportunities.
VEGF signaling intersects with mitochondrial biology in neurodegeneration[@mitchondria2024]. VEGF maintains mitochondrial function through PGC-1α-mediated mitochondrial biogenesis and preserves mitochondrial membrane potential. In neurodegenerative conditions, impaired VEGF signaling contributes to mitochondrial dysfunction and bioenergetic failure. Conversely, mitochondrial toxins reduce VEGF expression, creating a vicious cycle. Strategies targeting both VEGF signaling and mitochondrial health show promise in preclinical models.
VEGF influences autophagy, a critical process in neurodegeneration[@autophagy2023]. VEGF-induced AKT activation promotes autophagy through mTOR inhibition, helping clear protein aggregates. VEGF deficiency leads to impaired autophagic flux and accumulation of damaged proteins. In models of AD, PD, and ALS, VEGF administration enhances autophagy and reduces pathological protein inclusions. This autophagy modulation represents another mechanism through which VEGF provides neuroprotection.
Precision medicine for VEGF-based therapies will require biomarker-driven patient selection. Stratification based on VEGF levels, neurovascular unit integrity markers, genetic variants in VEGF pathway genes, and neuroimaging findings will enable targeted intervention. Patients with evidence of VEGF deficiency and neurovascular dysfunction may benefit most from VEGF enhancement, while those with compensatory VEGF elevation may require alternative approaches.
Given the complexity of neurodegenerative diseases, VEGF-targeted approaches will increasingly be combined with other interventions. Promising combinations include VEGF with anti-amyloid therapies, tau-targeted treatments, neurotrophic factors, and cellular therapies. Understanding the synergies between VEGF and other disease-modifying approaches will be critical for optimal therapeutic development.
The role of VEGF in early disease stages suggests potential for prevention strategies. Individuals at risk for AD or PD may benefit from lifestyle interventions that enhance VEGF signaling, including exercise, dietary approaches, and vascular risk factor management. Early VEGF modulation before significant neurodegeneration occurs may provide maximal benefit.