Fine structural and immunohistochemical identification of perineurial cells connecting proximal and distal stumps of transected peripheral nerves at early stages of regeneration in silicone tubes

Abstract

Perineurial cells are specialized connective tissue cells that form a barrier between endoneurium and epineurium in normal nerves. In the present study, the formation of the perineurium after transection of rat sciatic nerves was investigated. The cord bridging the gap between proximal and distal stumps through silicone tubes was studied 3, 7, 12, 18, and 21 days after surgery using electron microscopy and antibodies against epithelial membrane antigen (EMA), a marker for perineurial cells that has thus far not been applied to the study of differentiating cells in nerve tubulation systems. Initially, a thin cord consisting of fibrin bridged the gap between the stumps. At 7 days, longitudinal cells had migrated from both stumps toward the center of the tubes on the surface of the fibrin cord. These cells were immunoreactive with anti-EMA. At 12 days, ultrastructural features of perineurial cells (desmosomes, tight junctions, actin filaments with dense bodies, tonofilaments) were prominent in these cells. Subsequently, the gap was bridged through the perineurial tube by endothelial cells, pericytes, fibroblasts, Schwann cells, and axons. At 21 days, a single large nerve fascicle ensheathed by a mature perineurium was found between the stumps. Thus, the first cells to connect proximal and distal stumps in the investigated nerve regeneration silicon chamber system are perineurial cells. Through the tube formed by these cells, blood vessels and nerve fibers bridge the gap. Therefore, establishment of a perineurial connection between nerve stumps appears to be important in the sequence of events during nerve regeneration.

Assessment of Axonal Growth into Collagen Nerve Guides Containing VEGF‐Transfected Stem Cells in Matrigel

“…This orientation may be more important for regeneration guidance and growth than the actual ratio or number of axons in these intermediate units. Fibroblasts, perineurial cells, and Schwann cells are all involved in the ''incipient endoneurial restructuring'' of newly regenerated axons into minifascicles (Scaravilli, 1984;Popovic et al, 1994;Weis et al, 1994). Minifascicles tend to accompany axonal regeneration when and where the blood-nerve barrier has been breached (Stang et al, 2005), as demonstrated in this study.…”

“…The new vessels were apparently fragile, leading to several cases with hemorrhage, which would also contribute to an environment that is not supportive of axonal growth. The early presence of erythrocytes has been previously reported (Weis et al, 1994), but would typically be cleared by 21 days postoperative.…”

“…When axons regenerate through such conduits, a predictable sequence of events ensues (Lundborg, 2004). First, a fibrin clot forms, followed by migration of fibroblasts and perineurial cells into the chamber (Scaravilli, 1984;Schroder et al, 1993;Weis et al, 1994). Blood vessels and Schwann cells then infiltrate from both ends forming a bridge that traverses the chamber.…”

Preferential and Comprehensive Reconstitution of Severely Damaged Sciatic Nerve Using Murine Skeletal Muscle-Derived Multipotent Stem Cells

“…10 and 11 ) also benefits long nerve gap regeneration. According to several reports, perineurial cells are the first cells to reconnect the proximal and distal stumps after the experimental peripheral nerve lesion, and thereby form a guiding structure for re-growing Schwann cells and axons [23]–[27]. It is therefore possible that the capacity to form perineurium/endoneurium is a major advantage of Sk-MSC transplantation vs. other methods.…”

Enhanced Femoral Nerve Regeneration After Tubulization with a Tyrosine-Derived Polycarbonate Terpolymer: Effects of Protein Adsorption and Independence of Conduit Porosity

“…Within the first hours following nerve transection and conduit implantation, wound fluid rich in nerve-supporting factors fills from both nerve stumps into the conduit inner lumen. [65][66][67] During this process, the fibrin matrix (derived from plasma precursors) accumulates naturally to form a complete bridge across the chamber gap providing a substrate for cellular migration. 51 The E10-0.5(1K) conduit may encourage the early orientation of regenerating components on its own, as opposed to filling the inner lumen with a synthetic material to act as a longitudinal cable.…”