Perineurial cells are of mesenchymal origin and form the perineurium. The perineurium plays an important role in maintaining the integrity of the internal peripheral nerve environment by creating a physical barrier that, under physiologic condition, limits the entry of biologically active proteins, infectious agents, and blood-borne cells into the nerve bundles. The perineurial cells (PNC) are characterized by distinct ultrastructural features, including non-branching thin cytoplasmic processes coated by an external lamina and joined at their ends by a tight junction, few organelles, actin and vimentin filaments, and numerous pinocytotic vesicles. PNC are initially recruited from the surrounding mesenchyme to form a loose, permeable sheath around axons and Schwann cells, where they are separated by the extracellular matrix. These cells later undergo a mesenchymal-to-epithelial transition to form tight junctions and organize into the perineurium. PNC are immunoreactive for vimentin and epithelial membrane antigen but not for the Schwann cell marker S-100. HPNC from ScienCell Research Laboratories are isolated from human spinal nerve. HPNC are cryopreserved at passage one and delivered frozen. Each vial contains >5 x 105 cells in 1 ml volume. HPNC are characterized by immunofluorescence with antibodies specific to vimentin. HPNC are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast, and fungi. HPNC are guaranteed to further expand for 15 population doublings under the conditions provided by ScienCell Research Laboratories. Recommended Medium It is recommended to use Fibroblast Medium (FM, Cat. #2301) for culturing HPNC in vitro.