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

Objective 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. Methods 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. Results 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. Conclusion 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.