A re-assessment of the consequences of delayed transplantation of olfactory lamina propria following complete spinal cord transection in rats

This study is part of the NIH “Facilities of Research-Spinal Cord Injury” contract to support independent replication of published studies. We repeated a study reporting that delayed transplantation of olfactory lamina propria (OLP) into the site of a complete spinal cord transection led to significant improvement in hindlimb motor function and induced axon regeneration. Adult female rats received complete spinal cord transections at T10. Thirty days post-injury, pieces of OLP, which contains olfactory ensheathing cells (OECs), or respiratory lamina propria (RLP), which should not contain OECs, were placed into the transection site. Hindlimb motor function was tested using the BBB scale from day 1 post-injury through 10 weeks following transplantation. To assess axonal regeneration across the transection site, Fluorogold was injected into the distal segment, and the distribution of 5HT-containing axons was assessed using immunostaining. BBB analyses revealed no significant recovery after OLP transplantation and no significant differences between OLP vs. RLP transplant groups. Fluorogold injections into caudal segments did not lead to retrograde labeling in any animals. Immunostaining for 5HT revealed that a few 5HT-labeled axons extended into both RLP and OLP transplants and a few 5HT-labeled axons were present in sections caudal to the injury in 2 animals that received OLP transplants and 1 animal that received RLP transplants. Our results indicate that, although OLP transplants may stimulate regeneration under some circumstances, the effect is not so robust as to reliably overcome the hostile setting created by a complete transection paradigm.