Usefulness of sural nerve biopsy in the genomic era.

The value of peripheral nerve biopsy is now sometimes questioned due to the high complication rate and the recent development of noninvasive molecular techniques for diagnosis of hereditary neuropathy. However, the disorders that can be diagnosed by genetic analysis are limited and sural nerve biopsy is still a powerful tool for making a correct diagnosis of peripheral neuropathy. Histological evaluation of the sural nerve has long focused on changes of the two major components of peripheral nerves, axons and myelin, as well as on the detection of diagnostic changes such as amyloid deposits, sarcoid tubercles, and vasculitis. In addition to these components, the sural nerve biopsy specimen contains various important cells, including perineurial cells, mast cells, endothelial cells, pericytes, and lymphocytes. Among these cells, the endothelial cells and pericytes form the blood-nerve barrier (BNB) and investigation of these cells can reveal important information, especially in inflammatory neuropathies. To better understand the biological basis of BNB, we established rat and human immortal cell lines from the endothelial cells and pericytes of endoneurial microvessels. Characterization of these cell lines is now underway at our laboratory. These BNB cell lines should provide useful information concerning the pathophysiology of peripheral neuropathy, and we should obtain a new perspective for the investigation of nerve biopsy specimens after understanding the molecular background of the BNB.