Implications of olfactory lamina propria transplantation on hyperreflexia and myelinated fiber regeneration in rats with complete spinal cord transection.

Transplantation with olfactory ensheathing cells (OECs) has been adopted after several models of spinal cord injury (SCI) with the purpose of creating a favorable environment for the re-growth of injured axons. However, a consensus on the efficacy of this cellular transplantation has yet to be reached. In order to explore alternative parameters that could demonstrate the possible restorative properties of such grafts, the present study investigated the effects of olfactory lamina propria (OLP) transplantation on hyperreflexia and myelinated fiber regeneration in adult rats with complete spinal cord transection. The efficacy of OLP (graft containing OECs) and respiratory lamina propria (RLP, graft without OECs) was tested at different post-injury times (acutely, 2- and 4-week delayed), to establish the optimum period for transplantation. In the therapeutic windows used, OLP and RLP grafts produced no considerable improvements in withdrawal reflex responses or on the low-frequency dependent depression of H-reflex. Both lamina propria grafts produced comparable results for the myelinated fiber density and for the estimated total number of myelinated fibers at the lesion site, indicating that the delayed transplantation approach does not seem to limit the regenerative effects. However, animals transplanted with OLP 2 or 4 weeks after injury exhibit smaller myelin sheath thickness and myelinated fiber area and diameter at the lesion site compared to their respective RLP groups. Despite the ongoing clinical use of OECs, it is important to emphasize the need for more experimental studies to clarify the exact nature of the repair capacity of these grafts in the treatment of SCI.