Biomarkers of angiogenesis in Alzheimer's disease: Systematic review and meta-analysis

Background Cerebrovascular dysfunction can contribute to the pathophysiology of Alzheimer's disease (AD) and trigger angiogenesis. To date, no prior systematic review and meta-analysis (SRMA) study has attempted to qualitatively and quantitatively review existing literature examining angiogenic factors in AD. Objective In this review, we aimed to identify markers of angiogenesis in biofluids that can differentiate between individuals with AD and healthy older adults, and inform the role of angiogenesis in AD. Methods Using Medline (1946 to August 4, 2021), the literature was systematically searched for articles according to PRISMA guidelines. Angiogenesis and AD terms were searched as keywords and mapped to MeSH headings. A total of 18 studies (including 28 dependent effect sizes) were included in the meta-analysis. Hedges’ g was selected as the effect size of interest. Results A random-effects model including all eligible biofluid studies revealed a small and nonsignificant overall effect size (combined Hedges’ g = -0.26, 95% CI [-1.45, 0.92], p = 0.647), with significant heterogeneity (I 2 = 98.6%, p < 0.0001). Moderator analysis revealed no significant difference based on which specific angiogenic biomarker was examined (i.e., vascular endothelial growth factor (VEGF) versus others). Conclusions VEGF-related marker levels were not significantly different in AD and normal aging. Based on our findings, few studies have examined fibroblast growth factor and platelet-derived growth factor-related markers; however, we believe they warrant further investigation. Identifying novel angiogenic biomarkers could elucidate the role of vascular mechanisms in AD and reveal potential therapeutic targets.