Plasma levels of soluble Flt-1 and Tie-2 correlate with neovascularization in human carotid atherosclerotic plaques - a pilot study.

To determine whether circulating soluble Flt-1 (sFlt-1) and soluble Tie-2 (sTie-2) are associated with intraplaque neovascularization (IPN) in human carotid atherosclerotic plaques. Forty-four patients with ≥50% carotid stenosis underwent conventional carotid ultrasound and superb microvascular imaging (SMI); 29 had plasma collected and 11 provided carotid endarterectomy specimens for histology. IPN was quantified as neovessel counts in 2-minute SMI cine loops and as microvessel counts in excised plaques. Plasma VEGF-A/B/C/D, Ang-2, sFlt-1, and sTie-2 were measured by immunoassays. Public single-cell RNA-seq data from human carotid plaques were interrogated to map FLT1, TEK, VEGFA, ANGPT1, and ANGPT2 expression to specific plaque cell populations. IPN was detected in 33/44 (75%) patients, with 0-16 neovessels on SMI (median 4). Plasma sFlt-1 correlated with SMI neovessel counts (r=0.42, p=0.030), with a similar trend for sTie-2 (r=0.37, p=0.057), whereas VEGF-A/B/C/D and Ang-2 showed no significant relationships. In the surgical subgroup, histological neovessel counts correlated with sFlt-1 (r=0.65, p=0.030) and SMI neovessel count (r= 0.68, p =0.02) but not sTie-2. sFlt-1 and sTie-2 correlated with BMI (and sTie-2 also with age), yet log-sFlt-1 remained independently associated with SMI-derived neovessel counts after adjustment for age and BMI (B = 13.24, 95% CI 0.17-26.30, p=0.047; R²=0.18), while sTie-2 was not. No significant associations were observed between IPN or sFlt-1/sTie-2 and lipid profile, CRP, leukocyte counts, or other conventional risk factors. Single-cell transcriptomics showed FLT1 and ANGPT2 broadly expressed across endothelial, smooth-muscle, and myeloid clusters, with TEK largely confined to endothelial cells and ANGPT1 to smooth-muscle cells, supporting local activation of VEGF-FLT1 and Ang-TEK/Tie-2 signaling within plaques. In this pilot study, higher plasma sFlt-1, and, to a lesser degree sTie-2, correlated with carotid IPN on SMI and histology, independent of age and BMI. These findings suggest that soluble VEGF- and Ang/Tie-2-receptor pathways may serve as circulating, context-sensitive markers of intraplaque angiogenesis and plaque vulnerability, meriting evaluation in larger longitudinal cohorts.