Comparative spatial transcriptomic and single-cell analyses of human nail units and hair follicles demonstrate transcriptional similarities between the onychodermis and follicular dermal papilla

The nail unit and hair follicle are both hard keratin-producing organs that share various biological features. In this study, we demonstrated the presence of a nail-specific mesenchymal population called onychofibroblasts within the onychodermis. Onychodermis and follicular dermal papilla (DP) both expressed WNT and bone morphogenetic protein (BMP) signaling molecules. To analyze the function of BMP5 in nail development, we treated cultured human nail matrix keratinocytes (NMKs) with BMP5, which are highly expressed by onychofibroblasts. We observed increased expressions of hard keratin and HOXC13. We evaluated the effect of BMP5, which is highly expressed by onychofibroblasts, in nail-specific epithelial cells in vitro through the RNAseq analysis.