Substratum preferences of motor and sensory neurons in postnatal and adult rats

Abstract

After peripheral nerve injuries, damaged axons can regenerate but functional recovery is limited by the specific reinnervation of targets. In this study we evaluated if motor and sensory neurites have a substrate preference for laminin and fibronectin in postnatal and adult stages. In postnatal dorsal root ganglia (DRG) explants, sensory neurons extended longer neurites on collagen matrices enriched with laminin (~50%) or fibronectin (~35%), whereas motoneurons extended longer neurites (~100%) in organotypic spinal cord slices embedded in fibronectin-enriched matrix. An increased percentage of parvalbumin-positive neurites (presumptive proprioceptive) vs. neurofilament-positive neurites was also found in DRG in fibronectin-enriched matrix. To test if the different preference of neurons for extracellular matrix components was maintained in vivo, these matrices were used to fill a chitosan guide to repair a 6-mm gap in the sciatic nerve of adult rats. However, the number of regenerating motor and sensory neurons after 1 month was similar between groups. Moreover, none of the retrotraced sensory neurons in DRG was positive for parvalbumin, suggesting that presumptive proprioceptive neurons had poor regenerative capabilities compared with other peripheral neurons. Using real-time PCR we evaluated the expression of α5β1 (receptor for fibronectin) and α7β1 integrin (receptor for laminin) in spinal cord and DRG 2 days after injury. Postnatal animals showed a higher increase of α5β1 integrin, whereas both integrins were similarly expressed in adult neurons. Therefore, we conclude that motor and sensory axons have a different substrate preference at early postnatal stages but this difference is lost in the adult.

Nerve Guidance by a Decellularized Fibroblast Extracellular Matrix

“…For example, astrocyte migration was promoted on a laminin substrate but arrested on fibronectin [27]. Sensory neurons preferred a collagen matrix containing laminin over fibronectin for neurite outgrowth, whereas motor neurons preferred collagen enriched with fibronectin [28]. Neurite outgrowth from adult brain neurons was greater on fibronectin than on laminin [29].…”

Nerve regeneration by human corneal stromal keratocytes and stromal fibroblasts

“…Also, neurite counting fails to account for differences of neurite length. Concentric circle intersection count (CCIC) method has been used to quantify the extending neurites at different distances from a defined origin3942. However, no method validation has been reported and the accuracy of measurement can be influenced by the reproducibility of counting done by different observers.…”

Segregation of motor and sensory axons regenerating through bicompartmental tubes by combining extracellular matrix components with neurotrophic factors

“…Therefore, we have evaluated here if the addition of a different combinations of ECM molecules and NTFs into a collagen matrix was able to selectively promote the regeneration of MN and SN towards different distal fascicles. We chose the two matrix combinations based on previous in vitro findings using organotypic cultures that demonstrated a preferential effect of fibronectin and BDNF to promote neurite growth from MNs and of laminin and NGF/NT‐3 to promote neurite growth of SNs (González‐Pérez et al, ; Santos, González‐Pérez, Giudetti, Micera, Udina, Del Valle, & Navarro, ). The distal insert was selected to accommodate the size of the distal nerve with the number of axons of each type.…”

“…In fact, BDNF is a potent neurotrophic factor for MNs regeneration (Allodi et al, ; Boyd & Gordon, ; Vögelin et al, ), and it has been reported that the same intracellular mechanisms that promote axonal growth and cell survival are related with axonal guidance (Henle et al, ; Ming et al, ; Yuan et al, ). Furthermore, fibronectin also preferentially promotes motor axon outgrowth in vitro (González‐Pérez et al, ). In addition, it is possible that FN or BDNF act not only directly on the regenerating fibres but also they may promote the recruitment of motor‐related Schwann cells (Jesuraj et al, ).…”

“…In addition, different extracellular matrix (ECM) components constituents of the endoneurial tubes and the basal lamina play a role in the promotion of preferential axon outgrowth. For instance, laminin substrate mainly promotes sensory axon outgrowth in vitro (Gardiner, ; Plantman et al, ), whereas fibronectin enhances motor and proprioceptive axon outgrowth (González‐Pérez et al, ). Therefore, the addition of different combination of neurotrophic factors and ECM components in a Y‐tube model could be an interesting approach for segregating motor and sensory axons.…”