Heart valve interstitial cells (VICs) undergo activation and proliferation in repair and disease, but the mechanisms are not fully understood. We hypothesize that the establishment of N-cadherin/β-catenin cell-cell contacts may decrease VIC activation, and that Wnt3a/β-catenin signaling may increase VIC proliferation. VIC cultures of different densities are stained for α-SMA, cofilin, TGF-β, pSmad2/3, N-cadherin and β-catenin, and probed for phospho-β-catenin by Western blot. Low density VIC cultures are treated with exogenous Wnt3a and measured for cell number, proliferation, apoptosis, α-SMA, β-catenin, and β-catenin-mediated transcription. β-Catenin siRNA knockdown is used to assess β-catenin specificity. Increased staining of α-SMA, cofilin, TGF-β, pSmad2/3, nuclear β-catenin, and increased phospho-β-catenin are associated with few cell-cell contacts. Wnt3a increased VIC cell number, proliferation, nuclear β-catenin and β-catenin-mediated transcription without affecting activation and apoptosis, and proliferation is abolished by β-catenin siRNA. Thus, N-cadherin/β-catenin cell-cell contacts may inhibit VIC activation and Wnt3a/β-catenin signaling may increase VIC proliferation.

Heart valve interstitial cells (VICs) undergo activation and proliferation in repair and disease, but the mechanisms are not fully understood. We hypothesize that the establishment of N-cadherin/β-catenin cell-cell contacts may decrease VIC activation, and that Wnt3a/β-catenin signaling may increase VIC proliferation. VIC cultures of different densities are stained for α-SMA, cofilin, TGF-β, pSmad2/3, N-cadherin and β-catenin, and probed for phospho-β-catenin by Western blot. Low density VIC cultures are treated with exogenous Wnt3a and measured for cell number, proliferation, apoptosis, α-SMA, β-catenin, and β-catenin-mediated transcription. β-Catenin siRNA knockdown is used to assess β-catenin specificity. Increased staining of α-SMA, cofilin, TGF-β, pSmad2/3, nuclear β-catenin, and increased phospho-β-catenin are associated with few cell-cell contacts. Wnt3a increased VIC cell number, proliferation, nuclear β-catenin and β-catenin-mediated transcription without affecting activation and apoptosis, and proliferation is abolished by β-catenin siRNA. Thus, N-cadherin/β-catenin cell-cell contacts may inhibit VIC activation and Wnt3a/β-catenin signaling may increase VIC proliferation.