Increased Expression of Cyclo-Oxygenase 2 and Vascular Endothelial Growth Factor in Lesioned Spinal Cord by Transplanted Olfactory Ensheathing Cells

Olfactory ensheathing cells do not exhibit unique migratory or axonal growth-promoting properties after spinal cord injury

Olfactory ensheathing cells (OECs) have been reported to migrate long distances and to bridge lesion sites, guiding axonal regeneration after spinal cord injury (SCI). To understand mechanisms of OEC migration and axonal guidance, we injected lamina propria OECs 1 mm rostral and caudal to C4 SCI sites. One month later, OECs formed an apparent migrating cell tract continuously extending from the injection site through the lesion, physically bridging the lesion. Confocal immunolabeling demonstrated that, whereas this cell tract displaced host astrocytes, descending or ascending long tract axons did not preferentially extend into the cell tract and OECs failed to support bridging of corticospinal axons. Notably, the "bridging" tract of OECs formed within 1 h of cell injection, raising the possibility that cells passively spread from the pressure injection site rather than actively migrating. Control injections of bone marrow stromal cells (MSCs) or fibroblasts 1 mm from the lesion site also rapidly dispersed into the lesion cavity. Cell tracts extending into the lesion site were not seen when cells were injected either at low volumes, into spinal cord gray matter, or 3 d before or 9 d after SCI. OECs proliferated in injection sites, cell tracts, and lesion sites, indicating that OECs can also accumulate through cell proliferation. Thus, OECs do not appear to exhibit significant migratory properties when grafted to the spinal cord, exhibit no detectable difference in promoting axon growth into a SCI site compared with MSCs or fibroblasts, and do not support bridging of corticospinal axons beyond a dorsal column lesion.

Olfactory ensheathing glia and spinal cord injury: basic mechanisms to transplantation

The adult CNS, unlike its counterpart the peripheral nervous system (PNS), has little ability to repair itself after traumatic injury. Therefore, neurotrauma involving the brain or spinal cord has severe and long-lasting functional consequences for injured patients, as well as a massive financial and social impact on the affected families and the community at large. In particular, spinal cord injury (SCI) has provided scientists and clinicians with a challenging problem. In attempts to improve outcomes following SCI, numerous mammalian research models have been developed. Many of these models involve either transection or contusion injuries in rodents and experimental therapies include the transplantation of a range of cell types isolated from either the PNS or CNS. The authors focus on a cell type isolated from the olfactory system; olfactory ensheathing cells (OECs). Some basic tenets of olfactory cell biology, key preclinical results suggesting a role for OECs in stimulating spinal cord repair and the strengths and limitations of this potential therapy are discussed. The current and future status of OEC transplantation in the treatment of human SCI is also considered.

Effects of COX-2 and iNOS inhibitors alone or in combination with olfactory ensheathing cell grafts after spinal cord injury

STUDY DESIGN

We studied the effects of inhibitors of COX-2 (NS398) and iNOS (aminoguanidine) alone or in combination with olfactory ensheathing cell (OEC) grafts after spinal cord injury in the rat.

OBJECTIVE

To assess the role exerted by COX-2 and iNOS after spinal cord injury and an OEC transplant.

SUMMARY OF BACKGROUND DATA

COX-2 and iNOS exert a detrimental effect after spinal cord injury. In contrast, OECs grafted into the injured spinal cord mediate neuroprotection and also promote the up-regulation of COX-2 and iNOS.

METHODS

Photochemical injury was induced at T8 spinal cord segment. Rats received local injection of OECs (n = 15) or vehicle (DMEM; n = 15). Six subgroups of rats (n = 5 rats each) were given NS398 (DM-NS; OEC-NS), aminoguanidine (DM-AG; OEC-AG), or saline (DM-SS; OEC-SS). Locomotor ability, pain sensibility, tissue sparing, and density of blood vessels were evaluated.

RESULTS

Two weeks following injury, motor skills and nociceptive response were significantly higher in DM-NS and DM-AG than in DM-SS rats. The area of preserved spinal cord parenchyma was higher in treated animals than in those given saline. In contrast, functional outcome, tissue sparing, and density of blood vessels were lower in OEC-NS and OEC-AG than in OEC-SS animals.

CONCLUSIONS

These results suggest that, although COX-2 and iNOS exert a detrimental role after spinal cord injury, they may play an important role in the neuroprotective mechanisms induced by OEC grafts after spinal cord injury.

A clonal cell line from immortalized olfactory ensheathing glia promotes functional recovery in the injured spinal cord

Immortalized cell lines of olfactory ensheathing glia (OEG) that maintain the proregenerative properties of primary cultures provide an unlimited source of OEG for both basic and applied studies. Indeed, one specific immortalized rat OEG clonal line (TEG3) proved to be as good as primary OEG in promoting neuritogenesis and axon regeneration in culture models. Thus, we examined the capacity of TEG3 to promote axonal repair in an animal model of spinal cord injury, dorsal column crush. TEG3 cells can acquire astrocyte-like or Schwann cell-like morphology depending on the conditions under which they are cultured. In the injured spinal cord, prelabeled TEG3 survived for at least 10 weeks after grafting and they integrated into the spinal cord, adopting Schwann cell-like, astrocyte-like, or intermediate morphologies. In TEG3-transplanted animals, sensory projection axons grow into the lesion site and there was robust sprouting/axonal growth of the corticospinal tract, both into and beyond the lesion site, after crushing of the spinal cord-dorsal columns. TEG3-transplanted animals also recovered sensory and motor function in tape removal and beam walking behavioral tests. These data indicate that certain immortalized cell lines derived from a single cell can maintain the regenerative properties of primary OEG.

Chronic transplantation of olfactory ensheathing cells promotes partial recovery after complete spinal cord transection in the rat

The goal of this study was to ascertain whether olfactory ensheathing cells (OECs) were able to promote axonal regeneration and functional recovery when transplanted 45 days after complete transection of the thoracic spinal cord in adult rats. OECs promoted partial restitution of supraspinal pathways evaluated by motor evoked potentials and modest recovery of hindlimb movements. In addition, OEC grafts reduced lumbar reflex hyperexcitability from the first month after transplantation. Histological results revealed that OECs facilitated corticospinal and raphespinal axons regrowth through the injury site and into the caudal spinal cord segments. Interestingly, raphespinal but not corticospinal fibers regenerated long distances through the gray matter and reached the lower lumbar segments (L5) of the spinal cord. However, delayed OEC grafts failed to reduce posttraumatic astrogliosis. In conclusion, the beneficial effects found in the present study further support the use of OECs for treating chronic spinal cord injuries.

FK 506 reduces tissue damage and prevents functional deficit after spinal cord injury in the rat

We examined the efficacy of FK 506 in reducing tissue damage after spinal cord injury in comparison to methylprednisolone (MP) treatment. Rats were subjected to a photochemical injury (T8) and were given a bolus of MP (30 mg/kg), FK 506 (2 mg/kg), or saline. An additional group received an initial bolus of FK 506 (2 mg/kg) followed by daily injections (0.2 mg/kg intraperitoneally). Functional recovery was evaluated using open-field walking, inclined plane tests, motor evoked potentials (MEPs), and the H-reflex response during 14 days postoperation (dpo). Tissue sparing and glial fibrillary acidic protein (GFAP), biotinylated tomato lectin LEC, cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and interleukin 1 beta (IL-1 beta) immunoreactivity were quantified in the injured spinal cord. FK 506-treated animals demonstrated significantly better neurologic outcome, higher MEP amplitudes, and lower H-wave amplitude compared to that of saline-treated rats. In contrast, administration of MP did not result in significant differences with respect to the saline-treated group. Histologic examination revealed that tissue sparing was largest in FK 506-treated compared to saline and MP-treated animals. GFAP and COX-2 reactivity was decreased in animals treated with FK 506 compared to that in animals given MP or saline, whereas IL-1 beta expression was similarly reduced in both FK 506- and MP-treated groups. Microglia/macrophage response was reduced in FK 506 and MP-injected animals at 3 dpo, but only in MP-treated animals at 7 dpo with respect to saline-injected rats. Repeated administrations of FK 506 improved functional and histologic results to a greater degree than did a single bolus of FK 506. The results indicate that FK 506 administration protects the damaged spinal cord and should be considered as potential therapy for treating spinal cord injuries.

Acute and delayed transplantation of olfactory ensheathing cells promote partial recovery after complete transection of the spinal cord

The present study was undertaken to determine whether olfactory ensheathing cells (OECs) from the olfactory bulb were capable to promote axonal regeneration and functional recovery when transplanted either acutely or 1 week delayed into the T8 transected rat spinal cord. OEC transplants increased recovery of functional outcomes, as shown electrophysiologically by return of motor evoked potentials and by reduction of hindlimb hyperreflexia, and behaviorally by recovery of movements of hindlimb joints. Axonal regeneration was proven histologically by demonstrating long axonal outgrowth of raphespinal, coerulospinal, and corticospinal tracts within the caudal cord stump. Expression of GFAP and NG2 was down-regulated in perilesional cord segments in transplanted animals, indicating a more suitable environment for axonal regeneration. Overall, earlier recovery and better functional and histological results were observed in rats receiving acute than delayed OEC transplants. The beneficial effects obtained with transplantation after transection are encouraging for the application of OECs in the human injured spinal cord.