Expression of glial cell line-derived neurotrophic factor and GDNFR-alpha mRNAs in human peripheral neuropathies

The steady-state mRNA levels of glial cell line-derived neurotrophic factor (GDNF), GDNFR-alpha and RET were examined in various human peripheral neuropathies to determine the relationship with myelinated fiber pathology, and T cell and macrophage invasions in the diseased nerves. GDNF and GDNFR-alpha mRNA levels were elevated to variable extent in the diseased nerves, although they were not specific to the type of diseases. The increase of GDNFR-alpha mRNA levels was correlated with the extent of the nerves with axonal pathology, and was proportional to the extent of invasion of the nerves by T cells and macrophages. The GDNF mRNA levels were not related to axonal, demyelinating pathology, or inflammatory cell invasions. RET mRNA expression was not detected in normal nor diseased nerves. The GDNF and GDNFR-alpha expression in the diseased human nerves is regulated by an underlying pathology-related process, and could play a role in peripheral nerve repair.