Dose-Dependent Differential Effect of Neurotrophic Factors on In Vitro and In Vivo Regeneration of Motor and Sensory Neurons

Abstract

Although peripheral axons can regenerate after nerve transection and repair, functional recovery is usually poor due to inaccurate reinnervation. Neurotrophic factors promote directional guidance to regenerating axons and their selective application may help to improve functional recovery. Hence, we have characterized in organotypic cultures of spinal cord and dorsal root ganglia the effect of GDNF, FGF-2, NGF, NT-3, and BDNF at different concentrations on motor and sensory neurite outgrowth. In vitro results show that GDNF and FGF-2 enhanced both motor and sensory neurite outgrowth, NGF and NT-3 were the most selective to enhance sensory neurite outgrowth, and high doses of BDNF selectively enhanced motor neurite outgrowth. Then, NGF, NT-3, and BDNF (as the most selective factors) were delivered in a collagen matrix within a silicone tube to repair the severed sciatic nerve of rats. Quantification of Fluorogold retrolabeled neurons showed that NGF and NT-3 did not show preferential effect on sensory regeneration whereas BDNF preferentially promoted motor axons regeneration. Therefore, the selective effects of NGF and NT-3 shown in vitro are lost when they are applied in vivo, but a high dose of BDNF is able to selectively enhance motor neuron regeneration both in vitro and in vivo.

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

“…By manipulating the composition of the inside matrix of each branch, we attempted to preferentially attract the regenerating motor and sensory axons and then selectively guide them towards different distal nerves and their corresponding targets. In accordance with similar studies with gap defects (Clements et al, ; Meyer et al, ; Santos, González‐Pérez, Navarro, & del Valle, ), the division of the tube in two separated compartments did not suppose an obstacle for nerve regeneration as all the operated animals showed regeneration distal to the tube and evidence of functional reinnervation of skin and muscles. Tube repair leaving a short gap between proximal and distal nerve stumps was first presumed to allow axons to be guided towards their original distal fascicle by means of neurotropic diffusible factors (Evans, Bain, Mackinnon, Makino, & Hunter, ; Rende, Granato, Lo Monaco, Zelano, & Tcesca, ).…”

“…This result was corroborated by lack of differences in sensory functional recovery between both control and experimental groups. The lack of effect of LM + MP.NGF/NT‐3 on SNs was not expected as previous studies described a trophic and tropic guidance effect for laminin and NGF and NT‐3 individually assessed (Gallo et al, ; Santos, Giudetti, Micera, Navarro, & del Valle, , Santos, González‐Pérez, Navarro, & del Valle, ; Turney & Bridgman, ; Webber et al, ). One possible reason could be related with the heterogeneous populations of SNs (Usoskin et al, ) that reside in the DRG, in which approximately 70% of neurons express Trk receptors but of different subtypes whereas 30% are nonpeptidergic neurons and respond to Glial cell‐derived neurotrophic factor (GDNF) (Tucker & Mearow, ).…”

“…In the present study, a sciatic nerve transection was repaired with a bicompartmental tube containing a different combination of ECM and neurotrophic factors in each distal branch. Based on our previous results (Santos, González‐Pérez, et al, ; Santos, Giudetti, et al, ; Santos, González‐Pérez, et al, ), each compartment was filled prior to implantation with a collagen matrix containing either fibronectin with poly‐lactic co‐glycolic acid (PLGA) microspheres releasing BDNF (FN + MP.BDNF) in one side in contact with the distal peroneal nerve (P), or laminin with PLGA microspheres releasing NGF and NT‐3 (LM + MP.NGF/NT‐3) at the other side in contact with the tibial and sural nerves (T + S). We assessed whether regenerated motor axons preferentially grew in the first branch and sensory axons in the second branch, compared with control condition in which both branches contained the same collagen matrix and PLGA microspheres filled with PBS (Col + MP.PBS).…”

Combined Influence of Gelatin Fibre Topography and Growth Factors on Cultured Dorsal Root Ganglia Neurons

“…Curiously, the combination of fibres with GDNF led to poor neurite growth, as demonstrated by the low number and shorter neurites and a small occupied area detected in comparison to the control group. It is well known that GDNF sustains motor neuron survival and growth (Boyd and Gordon, ), however, it has been recently demonstrated that both low and high doses of GDNF are able to induce neurite outgrowth in cultured rat DRG (Santos et al, ). In cultured neurons, the expression of cRET is not changed in cells seeded on fibres, thus we can exclude that the absence of a GDNF‐based effect on fibres is due to a reduced number of GDNF‐responsive neurons.…”

Effect of Local Delivery of GDNF Conjugated Iron Oxide Nanoparticles on Nerve Regeneration along Long Chitosan Nerve Guide

“…Furthermore, we used NVR gel as a carrier for neurotrophic factors. In particular, we focus our attention on glial cell line-derived neurotrophic factor (GDNF), which is mainly involved in motor neuron regrowth and remyelination [14][15][16]. After nerve injury, endogenous growth factors are released by neuronal and glial cells from the distal nerve stump, and they can stimulate and guide axon regeneration; yet, this support is ineffective in regeneration over long distance and extended in time due to the short life of neurotrophic factors and the decline of their production [17,18].…”