Perineurial Cells (PNC)

Perineurium is a cellular ensheathment protecting the nerve fascicles, i.e., groups of Schwann cell-axon units, in the peripheral nerves. Perineurial Cells (PNC) divided slowly and their very large, flattened phenotype and their sheetlike growth patterns were distinct from those of the other connective tissue cells of peripheral nerves, such as Schwann cells or endoneurial fibroblasts. 

Perineurial Cells produced laminin and formed patches of basement membrane material on their surface. These characteristics are not associated with fibroblastic cells and the lack of S-100 protein differentiated the PN cells from the Schwann cells. Furthermore, cultured PNC expressed fibronectin which is not produced by Schwann cells. PNC showed characteristically prominent cytoplasmic actin containing stress fibers and staining with antibodies to vimentin showed arrays of intermediate filaments. The cells were negative for cytokeratin, glial fibrillary acidic protein, desmin, and factor VIII-related antigen indicating that they were not related to epithelial, glial, muscle-derived, or endothelial cells, respectively.