Abstract 18522: Pyridoxamine (vitamin B6) Mitigation Of Structural Valve Degeneration Of Bioprosthetic Heart Valves

Abstract

Introduction: Bioprosthetic heart valves (BHV) fabricated from glutaraldehyde treated bovine pericardium (BP) have limited durability due to structural valve degeneration (SVD) resulting from both calcification and advanced glycation end product (AGE) deposition. Hypothesis: We investigated the hypothesis that PYR modification of BHV leaflets mitigates AGE-serum protein uptake, oxidation, and calcification mechanisms in model studies, both in vitro and in vivo. Methods: To model AGE accumulation in BHV, we used well-established in vitro and in vivo models. AGE and serum albumin (SA) uptake in BP were quantitated per immunohistochemistry (IHC) staining intensity. PYR uptake was quantified using a novel fluorescent assay. BP collagen was examined by second-harmonic generation (SHG) microscopy. Calcification studies investigated the activity of BP alkaline phosphatase (ALP), and BP calcium levels were quantitated using a colorimetric assay. In vivo studies used a juvenile rat subdermal BP implantation model with PYR oral administration or BP-PYR modification. Endpoints were calcification, SA, and AGE accumulation per IHC and ALP activity per enzyme histochemistry. Results: PYR modification of BP resulted in high-affinity binding of PYR with 2.0±0.2 μg/mg of PYR binding to BP that was stable for 28 days in physiological conditions. Modification had an inhibitory effect on SA uptake in vitro with 60±5% (p<0.001) reduction in IHC staining intensity; PYR modification of BP resulted in increased protection from oxidative damage in vitro with collagen structure preservation (by SHG) after ten days, while control tissues were degraded. After 28-day of in vivo subdermal BP implantation in rats, a significant 70±5% (p<0.001) decrease and 80±5% (p<0.001) decrease in SA IHC staining and AGE staining, respectively, as well as ALP activity was documented in BP-PYR. Quantitative analysis of calcium content demonstrated a reduction from 108±5 μg/mg in control to 77±5 μg/mg in BP-PYR explants (p<0.001). Conclusions: Our study demonstrated that PYR mitigates SVD mechanisms in vitro and in vivo, limiting both AGE-serum protein accumulation and calcification with associated inhibition of ALP.