The regulatory role of the BDNF/TrkB pathway in organ and tissue fibrosis.

Fibrosis across diverse organ systems is one of the leading causes of morbidity and mortality by inducing progressive architectural remodeling and organ dysfunction. Brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase receptor B (TrkB) play crucial roles in regulating neural survival, development, function and plasticity in the central and the peripheral nervous system. Previous studies demonstrated that the BDNF/TrkB pathway is widely distributed in different cell types such as neuron, epithelial cell, hepatocyte, and cardiomyocyte. Recently, there is increasing recognition that BDNF and TrkB are also expressed in fibroblasts in different organs. Moreover, growing evidence was obtained regarding the functional roles of BDNF/TrkB signaling in organ and tissue fibrosis. Thus, this review summarizes the basic molecular characteristics of the BDNF/TrkB cascade and the findings of the crucial roles and therapeutic value in organ and tissue fibrosis including pulmonary fibrosis, hepatic fibrosis, renal fibrosis, cardiac fibrosis, bladder fibrosis and skin fibrosis. Small molecule BDNF mimetic and BDNF-related non-coding RNAs are also discussed for developing new therapeutic approaches for fibrotic disorders.