Taken together, our data show that, in the context of nonischemic HF, miR–129-5p expression in the LV — and specifically in CF — is downregulated and that miR–129-5p inhibits CF-to-MF and CF-to-OF transition via its targets SOX9 and ASPN and downstream β-catenin signaling. The gene discussed is SOX9; the disease is hydrops fetalis.