Long-Term Spinal Ventral Root Reimplantation, but not Bone Marrow Mononuclear Cell Treatment, Positively Influences Ultrastructural Synapse Recovery and Motor Axonal Regrowth

Abstract

We recently proposed a new surgical approach to treat ventral root avulsion, resulting in motoneuron protection. The present work combined such a surgical approach with bone marrow mononuclear cells (MC) therapy. Therefore, MC were added to the site of reimplantation. Female Lewis rats (seven weeks old) were subjected to unilateral ventral root avulsion (VRA) at L4, L5 and L6 levels and divided into the following groups (n = 5 for each group): Avulsion, sealant reimplanted roots and sealant reimplanted roots plus MC. After four weeks and 12 weeks post-surgery, the lumbar intumescences were processed by transmission electron microscopy, to analyze synaptic inputs to the repaired α motoneurons. Also, the ipsi and contralateral sciatic nerves were processed for axon counting and morphometry. The ultrastructural results indicated a significant preservation of inhibitory pre-synaptic boutons in the groups repaired with sealant alone and associated with MC therapy. Moreover, the average number of axons was higher in treated groups when compared to avulsion only. Complementary to the fiber counting, the morphometric analysis of axonal diameter and “g” ratio demonstrated that root reimplantation improved the motor component recovery. In conclusion, the data herein demonstrate that root reimplantation at the lesion site may be considered a therapeutic approach, following proximal lesions in the interface of central nervous system (CNS) and peripheral nervous system (PNS), and that MC therapy does not further improve the regenerative recovery, up to 12 weeks post lesion.

Direct Spinal Ventral Root Repair following Avulsion: Effectiveness of a New Heterologous Fibrin Sealant on Motoneuron Survival and Regeneration

“…The Wallerian degeneration processes that follow proximal axotomy became clear at the ipsilateral sciatic nerve, already at 4 weeks after injury, by the significant decrease in number of myelinated axons, combined with diminished mean values of myelin sheath, compatible to what has been described previously [7, 54]. On the contrary, 12 weeks after repair revealed improved number of fibers, indicating regeneration, regardless the fibrin sealant used.…”

Nerve Root Reimplantation in Brachial Plexus Injuries

“…These have been particularly useful in minimizing neuronal apoptosis. Among them are induced pluripotent stem cells (iPSC) [143], mesenchymal stem cells (MSCs) [168][169][170], olfactory ensheathing glial cells (OECs) [85,171], bone marrow stem cells (BMC) [172], human fibroblast growth factor 2 (FGG2) [95], neuroectodermal stem cells (ESC) [143], murine neural crest stem cells (MNCSC) [173], embryonic stem cell-derived neuron precursors (ESCDNP) [173] and neural progenitor cells (NPC) [140,141,168,174]. The human embryonic stem cells overexpressing human fibroblast growth factor 2 (FGG2) applied at the injury site improved MN survival and reduced the glial reactivity, thus improving the regenerating capacities [95].…”

Clinical and neurobiological advances in promoting regeneration of the ventral root avulsion lesion

“…Directly following the avulsion, activated microglia and astrocytes are found to enwrap the soma of axotomized motoneurons and parasympathic preganglionic neurons (Emirandetti et al, 2006;Penas et al, 2009;Scorisa et al, 2009). Ultrastructural analysis shows a loss of synapses on the cell bodies of motoneurons following axotomy, a process also referred to as synaptic stripping (Linda et al, 2000;Barbizan et al, 2014b). Astroglial activation following axotomy appears to be causal to synaptic retraction from motoneuron cell bodies (Aldskogius et al, 1999;Emirandetti et al, 2006;Penas et al, 2009).…”