Table 5.

Summary Statement for Olfactory Ensheathing Cell Transplantation

Pros	Cons
Demonstrates good integration into host spinal cord; claims of axonal sprouting/regeneration reported.	No robust behavioral benefits after transplantation into moderate or severe thoracic contusion injuries.
Behavioral improvements have been frequently reported, albeit after partial or full transection SCI models. Improvements may be due to some axonal regeneration, although trophic effects on host spinal cord likely play a role.	Efficacy of olfactory lamina propria pieces in chronic thoracic transection models could not be formally replicated.
Offer the possibility of autologous transplantation, although human protocols for such procedure still need refinement (see below)	In many cases, appears to require adjuvent treatment to increase efficacy (e.g. Schwann cells, Matrigel, rolipram, cAMP, neurotrophic factors)
Knowledge Gaps
The body of literature focused mainly on partial or full laceration models, which are clinically rare. More data on the performance of these cells in contusion injuries is needed.
Efficacy in a chronic injury model is currently lacking, and is particularly important given that this cell transplantation strategy has been forwarded into human patients with chronic SCI.
Only one study published on human olfactory bulb derived cells in the injured spinal cord.
A better understanding of the possible effects on sensory perception and provocation of pain is needed.
Optimization of biomaterials to support survival and OECs bridging lacerations is still desirable.