In HFs at the anagen stage and catagen stage, we further analyzed the protein–protein interaction (PPI) network of core KEGG pathways and identified 20 genes, namely TGFB2, FGF13, TYR, WNT7B, WNT7A, WNT16, FZD1, FZD9, THBS2, TNC, ITGA2, ITGA5, SFRP1, NTRK2, INSR, KDR, CSF1, PDGFA, FGFR1, and PDGFRA, that may participate in HF development and growth (Figure 3D). The gene discussed is SFRP1; the disease is hydrops fetalis.