Optimal treatment of tannic acid for the anti-calcification of bovine jugular veins and the underlying mechanism.

Objectives: To evaluate the effects of combined treatment with tannic acid and ferric ions on the biomechanical and anti-calcification properties of glutaraldehyde-fixed bovine jugular veins after xenografting.

Methods: Two-point bending test and uniaxial tensile test were used to evaluate the flexural and biomechanical properties; Subcutaneous implantation in rat and right ventricular outflow tract reconstruction of sheep were used to evaluate the anti-calcification effects; The performance of the graft in sheep models was evaluated every month after the surgery with echocardiography examination. Markers of macrophages, T lymphocytes, smooth muscle cell osteogenic differentiation and matrix metalloproteinases in sheep explants were detected by immunohistochemistry.

Results: The flexibility of the bovine jugular veins cotreated with ferric ions-tannic acid was improved while maintaining biomechanical properties and excellent anti-calcification effects. Echocardiography results showed that the grafts functioned well in the animals without stenosis or reflux of the valve. Immunohistochemical studies showed that the osteogenic differentiation marker (Runx2) was detected in calcified regions and colocalised with the SMC marker (α-SMA). Compared to the glutaraldehyde-treated samples, T-cell marker (CD3), matrix metalloproteinase-2 and 9 expressions were reduced in the ferric ions-tannic acid treated group.

Conclusion: Ferric ions-tannic acid treatment can give the conduits better flexibility with excellent biomechanical properties and anti-calcification effects, making it a promising bovine jugular veins processing method.