Validation of a Gravitational Model to Study Local Endogenous Biomarkers in Chronic Venous Insufficiency

Unlike most systemic chronic diseases, chronic venous insufficiency (CVI) is ideal to study using endogenous biomarkers. The stimulus causing damage can be turned on and off with gravitational positioning and venous blood samples can be taken locally. Annexin V (apoptosis) and microparticles (cell membrane debris) were used as markers of cell destruction, with matrix metalloproteinases (MMPs) as markers of tissue remodelling. The aim of this proof of concept study was to validate a gravitational model by investigating whether standing induced biochemical stress and whether recovery occurs on lying and after compression.

Fourteen patients (C_4a-b) and 14 volunteers (C_0-1) were tested under three supervised laboratory conditions for 1 h on separate days: (i) stationary standing on a small paper square; (ii) lying with both legs elevated 20°; (iii) compression standing using a 23-32 mmHg below knee stocking. Immediately after each condition, venous blood was withdrawn from the ankle. Commercial enzyme linked immunosorbent assay kits were used for batch analysis of the plasma samples.

Median (interquartile range [IQR]) values of annexin V (AU/mL) and microparticles (nM) standing were as follows: volunteers 2.9 (2 - 3.4) and 10.2 (8.8 - 13.8), and patients 2.2 (1.3 - 6) and 11.3 (7.7 - 20), respectively. Significant reductions were observed lying: volunteers 2.1 (1.5 - 2.7; p = .019) and 8.5 (7.4 - 9.4; p = .041), patients 1.7 (1.2 - 2.7; p = .004) and 8.5 (7.0 - 11.4; p = .041), respectively. Globally, all median MMP values in the patients reduced with lying and with compression versus standing (p = .004). Individually, significant reductions occurred in MMPs 2 and 13 with compression and MMPs 3, 7, 8, 9, 10, and 12 on lying. Lying was more effective at reducing MMP levels than compression.

Annexin V and microparticle concentrations are responsive to elevation and compression after 1 h. In the patients, all the tested MMPs decreased after lying and with compression versus standing. This model provides evidence supporting gravitational protection in the treatment of CVI.