Uncoupling of Microvascular Blood Flow and Capillary Density in Vascular Cognitive Impairment
Chenxing Eleana Zhang1,2, Julie Staals1,2, Robert Jan van Oostenbrugge1,2
1Department of Neurology, Maastricht University Medical Center, Maastricht, Netherlands.
Insights
In patients with vascular cognitive impairment (VCI) due to cerebral small vessel disease (cSVD), capillary density fails to increase with blood flow. This flow-density uncoupling may impair nutrient delivery and cause tissue damage.
Area of Science:
- Neuroscience
- Vascular Biology
- Microcirculation Research
Background:
- Cerebral small vessel disease (cSVD) is a significant contributor to dementia and vascular cognitive impairment (VCI).
- Emerging evidence suggests capillary dysfunction, not just flow limitation, is key in cSVD.
- cSVD is increasingly viewed as a systemic microvascular disorder.
Purpose of the Study:
- To investigate sublingual microvascular blood flow and capillary density in VCI patients with cSVD compared to controls.
- To determine if capillary density adjusts to changes in microvascular blood flow in VCI.
- To explore the relationship between flow and density in the microvasculature of VCI patients.
Main Methods:
- Intravital microscopy was used to examine sublingual microvessels in 15 VCI patients and 15 controls.
- Microvascular blood flow and capillary density were quantified in high and low flow areas.
- Flow-density coupling was assessed by analyzing ratios of density to flow changes and red blood cell (RBC) velocities.
Main Results:
- Healthy controls showed proportional increases in capillary density with elevated feed vessel blood flow.
- VCI patients did not exhibit an increase in capillary density despite increased feed vessel RBC velocity.
- Flow-density coupling significantly differed between VCI patients and controls, even after adjusting for age and hypertension.
Conclusions:
- Patients with VCI due to cSVD demonstrate an uncoupling of microvascular blood flow and capillary density.
- This impaired flow-density coupling may hinder oxygen and nutrient exchange during increased metabolic demand.
- The findings suggest a potential mechanism for tissue damage in VCI driven by microvascular dysfunction.
Abstract:
Cerebral small vessel disease (cSVD) plays an important role in dementia and is a major cause for vascular cognitive impairment (VCI). Recent studies hypothesized that capillary dysfunction including reduction of capillary patency, rather than a flow-limiting pathology is crucial in cSVD. As cSVD is considered a systemic microvascular disease, we examined sublingual microvascular blood flow and capillary density in patients with VCI and controls. Fifteen patients with VCI due to cSVD and 15 controls underwent intravital microscopy of the sublingual microvessels. Microvascular blood flow and capillary density in high and low flow areas were determined for each participant. Flow-density coupling was examined by determining the ratio of density changes to flow changes, and the ratio of feed vessel red blood cell (RBC) velocity to capillary RBC velocity. These were compared between VCI and controls. In healthy controls, capillary density increased proportionally with feed vessel blood flow increase. In patients with VCI, no increase of capillary density was observed. Moreover, increase of feed vessel RBC velocity led to significant increase of capillary RBC velocity in VCI, whereas in controls, the capillary RBC increased only slightly. Flow-density coupling differed significantly between VCI and controls, also after correcting for age and hypertension. Our findings suggest uncoupling of microvascular blood flow and capillary density in patients with VCI. This uncoupling may impair oxygen and nutrients exchange when blood flow increases in response to increased metabolic demand, ultimately leading to tissue damage.
