The Blood-Nerve Barrier: Structure and Functional Significance

Abstract

The blood-nerve barrier (BNB) defines the physiological space within which the axons, Schwann cells, and other associated cells of a peripheral nerve function. The BNB consists of the endoneurial microvessels within the nerve fascicle and the investing perineurium. The restricted permeability of these two barriers protects the endoneurial microenvironment from drastic concentration changes in the vascular and other extracellular spaces. It is postulated that endoneurial homeostatic mechanisms regulate the milieu intérieur of peripheral axons and associated Schwann cells. These mechanisms are discussed in relation to nerve development, Wallerian degeneration and nerve regeneration, and lead neuropathy. Finally, the putative factors responsible for the cellular and molecular control of BNB permeability are discussed. Given the dynamic nature of the regulation of the permeability of the perineurium and endoneurial capillaries, it is suggested that the term blood-nerve interface (BNI) better reflects the functional significance of these structures in the maintenance of homeostasis within the endoneurial microenvironment.

Human adipose-derived stem cells stimulate neuroregeneration

“…Approximately 40 % of sensory neurons diminish within 2 months after peripheral axotomy. Similar phenomena are also observed clinically following peripheral nerve injury [11]. Swelling occurs following nerve damage in the proximal segment, while the distal stump undergoes degeneration; however, regenerating axons can be detected as early as 24 h following the injury.…”

“…The recorded high rate of neuronal death in our experimental groups is undoubtedly associated with serious traumatization of the sciatic nerve and the two suture lines create a serious obstacle for the regenerating axons [11]; however, the transplantation of the hADSCs considerably contributes to the neuronal survival of the L5 spinal ganglion after the autonerve grafting. We have found that it is only in the group with the cell stimulation, and exclusively in the neurons of a large diameter, that doubling of nucleoli Red fluorescence corresponds to the positive reaction with caspase-9.…”

Painful Terminal Neuroma Prevention by Capping PRGD/PDLLA Conduit in Rat Sciatic Nerves

“…At the early stage of inflammation, the release of chemokines and increase in the permeability of blood–nerve barrier were accomplished simultaneously 30. Blood‐borne macrophages attracted from surrounding circumstance would traverse these vessels along the gradient and the majority of active macrophages was hematogenous.…”

Extrinsic cellular and molecular mediators of peripheral axonal regeneration

“…Successful regeneration is a consequence of well orchestrated interactions between axotomized neurons and non-neuronal cells, especially Schwann cells and macrophages. These interactions are triggered upon injury and initiate a cascade of cellular and molecular reactions including local damage of the blood-nerve-barrier (Weerasuriya and Mizisin 2011;Gray et al 2007;Bouldin et al 1991), degeneration of the distal part of severed axons (Tsao et al 1999;Perry et al 1990;Lubinska 1977), dedifferentiation and proliferation of Schwann cells (LeBlanc and Poduslo 1990), recruitment of hematogenous macrophages LeBlanc and Poduslo 1990), reorganization of the endoneurial extracellular matrix (ECM) (Gantus et al 2006;Tona et al 1993), as well as the release of cytokines, neurotrophins and growth factors (Gordon 2009;Ruohonen et al 2005;Shamash et al 2002). In this way, an axon growthpermissive microenvironment is formed predominantly by non-neuronal adjacent cells, which significantly enhances the intrinsic growth potential of injured peripheral neurons.…”