We previously reported that the interstitial cystitis (IC) induced expression of some Reg family members in Cyclophosphamide-induced cystitis model of rat, and demonstrated that PAP-III (Reg-IIIγ in humans) was expressed in the urothelium of the bladder and, on the other hand, that PAP-I (HIP/PAP in humans) was expressed in primary afferent neurons of dorsal root ganglia that innervate the bladder. This evidence concerns the gene REG3A and chronic cystitis.