Abstract 350: Human Cardiac Fibroblasts Have Angiogenic Inhibitory Phenotypes Through Their Expressing Lypd1 In Vitro

Abstract

Bioengineered cardiac tissues are expected to use for regenerative medicine and tissue model, and tissue vascularization is necessary for fabricating three dimensional thickened cardiac tissues. Consistent with the evidence that fibroblasts are major component cells in heart, they are also imperative for fabricating bioengineered cardiac tissues. Although fibroblasts exist in many tissues and organs, tissue-specific phenotypes of fibroblasts remain unclear, which might make it difficult to fabricate bioengineered tissues close to the biological tissues. As bioengineered tissues provide the micromilieu for mutual communication among multilineage cells, we attempted to identify cardiac fibroblast-specific function against endothelial cells in comparison with dermal tissue-derived fibroblasts and the underlying mechanisms. When human atrial or ventricular cardiac fibroblasts (NHCFa or NHCFv) and dermal tissue-derived fibroblasts (NHDF) were co-cultured with various types of human endothelial cells including HUVEC for 3 days, NHCFa and NHCFv, but not NHDF, significantly inhibited CD31 positive endothelial cell network formation (NHCFa: 1.3±0.3, NHCFv: 2.3±0.1, NHDF: 4.6±0.7, n=3, p<0.05). Then we hypothesized that cardiac fibroblasts express angiogenesis inhibitory factors. We identified genes that were highly expressed in cardiac fibroblasts and encoded extracellular proteins through microarray analysis. After evaluating the effects of candidate genes on endothelial cell network formation by siRNA transfection to cardiac fibroblasts, Ly6/Plaur domain-containing 1 (LYPD1) was identified as the responsible factor. Next we generated recombinant LYPD1 (rLYPD1) and elucidated the effect of rLYPD1 on angiogenesis. Robust endothelial cell network formation in co-culture with NHDF was attenuated with the treatment with rLYPD1 and endothelial tube formation on Matrigel was also remarkably inhibited in the presence of rLYPD1, suggesting that LYPD1 has an angiogenesis inhibitory function. These findings indicate that human cardiac fibroblasts have angiogenesis inhibitory phenotypes through LYPD1 in vitro and inhibition of LYPD1 will be necessary for fabricating vascularized bioengineered cardiac tissues.