901-118 Cellular Expression of Matrix Proteins Mediates Calcification in Native Human and Bioprosthetic Heart Valves

Abstract

Dystrophic mineralization remains the leading cause of valve stenosis and failure in native human (NHV) and porcine bioprosthetic (PBV) heart valves. We hypothesized that expression of noncollagenous matrix proteins (MP) that induce skeletal mineralization may orchestrate valvular calcification (Ca 2+ ). 18 porcine PBV and 13 NHV obtained during replacement surgery were analysed for cells, calcium, fibrosis and vessels. Immunostaining for macrophages, T-cells, α-smooth muscle (SM) actin, osteopontin (OP), osteocalcin (OC) and osteonectin (ON) was performed with non-immune sera as controls. In situ hybridization analysis utilized antisense oligonucleotide probes for OR OC, ON and sense controls. Results were compared to known positive/negative tissue controls and normal heart valves. A probe averaged in situ score was calculated for each valve. MP in situ was graded positive if ≥2 different probes exhibited >5 signal positive cells/slide. Valves were divided into 4 groups based on presence of calcium: I: PBV non-Ca 2+ (n = 8); II: PBV-Ca 2+ (n = 10); III: NHV-Ca 2+ (n = 8); IV: NHV non-Ca 2+ (n = 5). 2 × 2 contingency table analysis of in situ signal status revealed: Positive PBV (I vs II) 0.03 * versus NHV (III vS IV) 0.01 * negative PBV-Ca 2+ and NHV-Ca 2+ (II vs III) 1.00 in situ PBV-Ca 2+ vs NHV-NonCa 2+ 0.005 * * Significant p value by Fisher's Exact Test Comparison of mean in situ scores revealed significant differences among groups III vs IV and I vs IV PBV age (p < 0.001) and NHV cellularity (p < 0.003) correlated with calcium. For all valves: OR OC and ON mRNA expression localized with calcification and cellular infiltration; immunostaining identified macrophages, OR OC and ON at the calcification front; SM were associated with valve edges and cuspal Ca 2+ . (1) Cell-mediated calcification is promoted by matrix protein expression common to PBV and NHV; (2) matrix protein mRNA expression is quantitatively related to extent and localization of valvular mineralization; (3) macrophage infiltration is closely associated with matrix protein expression and calcification.