Novel Insights Into the Pathways Regulating the Canine Hair Cycle and Their Deregulation in Alopecia X

The 2017 study "Novel insights into the pathways regulating the canine hair cycle and their deregulation in alopecia X" investigated the molecular pathways involved in Alopecia X, a hair cycle arrest disorder in Pomeranians. The researchers performed transcriptome profiling on skin biopsies from 5 affected and 4 non-affected Pomeranians. They found a downregulation of key regulator genes of the Wnt and Shh pathways, which are known to result in stem cell activation and differentiation in mice. This aligns with the lack of anagen hair follicles in dogs with Alopecia X. Additionally, they observed a significant downregulation of the stem cell markers SOX9, LHX2, LGR5, TCF7L1 and GLI1, while NFATc1, a quiescence marker, was upregulated. Genes coding for enzymes directly involved in the sex hormone metabolism were also differentially regulated in Alopecia X, supporting the proposed but unproven deregulation of the sex hormone metabolism in this disease. The study concluded that the canine hair cycle is regulated by similar signaling pathways as in mice and that there is a deregulation of genes maintaining the stem cell compartment and the hair cycle in Alopecia X dogs. The data also strongly supported the previously established hypothesis that the steroid hormone metabolism is altered in Pomeranians with Alopecia X.