# The association between circulating CD34+CD133+ endothelial progenitor cells and reduced risk of Alzheimer’s disease in the Framingham Heart Study

## TL;DR

This study finds that a specific type of blood cell is linked to a lower risk of Alzheimer's disease, especially in people with certain genetic traits and vascular issues.

## Contribution

The study identifies CD34+CD133+ endothelial progenitor cells as a novel protective factor against Alzheimer’s disease.

## Key findings

- CD34+CD133+ endothelial progenitor cells are dose-dependently associated with reduced Alzheimer’s disease risk.
- The protective effect of CD34+CD133+ cells is significant in individuals with hypertension and cerebral microbleeds.
- Genetic variants in KIRREL3 and EXOC6B genes modulate the association between CD34+CD133+ cells and Alzheimer’s risk.

## Abstract

Endothelial dysfunction has been associated with both cerebrovascular pathology and Alzheimer’s disease (AD). However, the connection between circulating endothelial cells and the risk of AD remains uncertain. The objective was to leverage data from the Framingham Heart Study to investigate various circulating endothelial subtypes and their potential correlations with the risk of AD.

The study conducted data analyses using Cox proportional hazard regression and linear regression methods. Additionally, genome-wide association study (GWAS) was carried out to further explore the data.

Among the eleven distinct circulating endothelial subtypes, only circulating endothelial progenitor cells (EPCs) expressing CD34+CD133+ were found to be negatively and dose-dependently associated with reduced AD risk. This association persisted even after adjusting for age, sex, years of education, apolipoprotein E (APOE) ε4 status, and various vascular diseases. Particularly noteworthy was the significant association observed in individuals with hypertension and cerebral microbleeds. Consistently, positive associations were identified between CD34+CD133+ EPCs and specific brain regions, such as higher proportions of circulating CD34+CD133+ cells correlating with increased volumes of white matter and the hippocampus. Additionally, a GWAS study unveiled that CD34+CD133+ cells influenced AD risk specifically in individuals with homozygous genotypes for variants in two stem cell-related genes: kirre like nephrin family adhesion molecule 3 (KIRREL3, rs580382 CC and rs4144611 TT) and exocyst complex component 6B (EXOC6B, rs61619102 CC).

The findings suggest that circulating CD34+CD133+ EPCs possess a protective effect and may offer a new therapeutic avenue for AD, especially in individuals with vascular pathology and those carrying specific genotypes of KIRREL3 and EXOC6B genes.