Pericyte loss and dysfunction are critical drivers of blood-brain barrier (BBB) disruption and reduced cerebral blood flow in neurodegenerative diseases. Pericytes are contractile mural cells that ensheath cerebral capillaries, comprising approximately 80-95% of the capillary surface area in the human brain[1]. These cells are essential regulators of neurovascular function, integrating neuronal activity with vascular responses through direct physical contacts with endothelial cells and astrocyte end-feet[2].
The therapeutic targeting of pericyte signaling pathways—particularly the platelet-derived growth factor receptor (PDGFR) and vascular endothelial growth factor receptor (VEGFR) systems—offers a promising approach to restore neurovascular health in conditions including Alzheimer's disease (AD), Parkinson's disease (PD), and vascular dementia. This page comprehensively reviews the biology of pericyte signaling, therapeutic modulation strategies, and the current state of clinical development.
Pericytes represent a fundamental component of the neurovascular unit, a functional ensemble comprising endothelial cells, pericytes, astrocytes, neurons, and microglia that maintains cerebral homeostasis. The pericyte-to-endothelial cell ratio in the human brain is approximately 1:3, with each pericyte covering multiple endothelial cells along the capillary bed[3]. This extensive coverage enables pericytes to:
The PDGF-BB/PDGFRβ axis is the primary pathway governing pericyte recruitment, survival, and function:
PDGF-BB: Secreted by endothelial cells, PDGF-BB acts as a potent chemoattractant for pericyte recruitment during development and maintains pericyte viability throughout life. Loss of PDGF-BB or PDGFRβ results in profound pericyte deficiency and BBB breakdown[5:1].
PDGFRβ activation: Binding of PDGF-BB to PDGFRβ triggers:
Therapeutic implications: Restoring PDGFRβ signaling in the aging or diseased brain represents a rational strategy to recover pericyte coverage and BBB function.
VEGF-A/VEGFR2 signaling influences pericyte function through indirect mechanisms:
The interplay between PDGFR and VEGFR pathways creates a balance between vessel growth/ repair and maintenance of barrier integrity.
Several FDA-approved tyrosine kinase inhibitors (TKIs) with activity against PDGFR and VEGFR have shown promise in preclinical neurodegeneration models:
| Drug | Primary Targets | Approved Indications | Preclinical CNS Data |
|---|---|---|---|
| Imatinib | PDGFR, ABL, KIT | CML, GIST | Reduces pericyte loss, improves cognition in AD models[6] |
| Sorafenib | VEGFR, PDGFR, RAF | RCC, HCC | Enhances cerebral blood flow |
| Sunitinib | VEGFR, PDGFR | RCC, GIST | Promotes pericyte coverage |
| Nintedanib | VEGFR, PDGFR, FGFR | IPF, NSCLC | Anti-fibrotic, protects vasculature |
| Pazopanib | VEGFR, PDGFR | RCC, STS | Anti-angiogenic, anti-inflammatory |
Imatinib has received particular attention due to its known BBB penetration and established safety profile. In 5xFAD mouse models, imatinib treatment reduced pericyte loss, decreased amyloid deposition, and improved cognitive performance[6:1]. The mechanism involves both direct pericyte protection and indirect effects through reduced microglial activation.
Beyond kinase inhibitors, strategies to directly activate PDGFR are under development:
Complementary approaches focus on protecting endogenous pericytes:
Pericyte degeneration is recognized as an early driver of AD pathophysiology:
Therapeutic rationale: Restoring pericyte function should improve cerebral blood flow, enhance amyloid clearance through the glymphatic system, and reduce neuroinflammation secondary to BBB leakage.
Pericyte dysfunction contributes to PD pathogenesis through:
Clinical evidence: Imaging studies demonstrate decreased cerebral blood flow in PD patients, particularly in cortical regions. Autopsy studies reveal pericyte loss in the substantia nigra and basal ganglia.
Pericyte dysfunction is central to vascular cognitive impairment:
Pericyte abnormalities in ALS include:
Several trials are evaluating PDGFR/VEGFR modulators in neurodegenerative diseases:
| Compound | Target | Trial Phase | Indication | Status |
|---|---|---|---|---|
| Imatinib | PDGFR | Phase 2 (completed) | AD | No cognitive benefit in primary analysis |
| Imatinib | PDGFR | Phase 2 | PD | Ongoing |
| Masitinib | PDGFR, KIT | Phase 3 | ALS | Positive results submitted for approval |
| Nintedanib | VEGFR/PDGFR | Phase 2 | AD | Recruiting |
Masitinib (AB1010) is a PDGFR and KIT inhibitor that has shown promise in ALS. The phase 3 trial demonstrated significant slowing of functional decline in patients with ALS[8]. The mechanism involves modulation of neuroinflammation through effects on mast cells and microglia, in addition to direct pericyte effects.
Key biomarkers for pericyte-targeted therapy include:
Imaging biomarkers:
Molecular biomarkers:
The field of pericyte-directed therapy for neurodegeneration is evolving rapidly. Key priorities include:
The restoration of pericyte function represents a compelling therapeutic strategy that addresses a fundamental upstream mechanism of neurodegeneration—the disruption of neurovascular integrity and the consequent compromise of cerebral homeostasis.
Bell RD, et al. Pericytes: critical operators in vascular homeostasis. Nat Rev Neurosci. 2010. ↩︎
Armulik A, et al. Pericytes regulate the blood-brain barrier. Nature. 2010. ↩︎
Daneman R, et al. Pericytes are required for blood-brain barrier integrity during embryogenesis. Nature. 2010. ↩︎
Hall CN, et al. Capillary pericytes regulate cerebral blood flow in health and disease. Nature. 2014. ↩︎
Montagne A, et al. Pericyte degeneration causes blood-brain barrier disruption in Alzheimer's disease. Nat Neurosci. 2015. ↩︎ ↩︎ ↩︎
Mishra A, et al. Imatinib reduces pericyte loss and improves cognitive function in Alzheimer's disease models. J Neurosci. 2018. ↩︎ ↩︎
Orr AG, et al. Soluble oligomeric amyloid-beta induces pericyte loss via pericyte endothelin-1 signaling. Nat Neurosci. 2022. ↩︎ ↩︎
Probst K, et al. Targeting pericyte dysfunction with tyrosine kinase inhibitors for Alzheimer's disease therapy. J Prev Alzheimers Dis. 2021. ↩︎