Bridging the divide: spinal cord repair by cellular transplantation--from research laboratory to therapeutic application

Designing clinical trials in canine spinal cord injury as a model to translate successful laboratory interventions into clinical practice

Many interventions have been shown to improve outcome after experimental spinal cord injury in laboratory animals. The challenge now is to determine whether any of these can be translated to become an efficacious therapy for clinical lesions - a process that is often difficult and frequently fails. Here, we discuss the steps that are required to make this transition and the need for rigorous clinical trials. A key component is an outcome measure that is amenable to statistical analysis; we describe methods that we have developed to accurately measure function after spinal cord injury in dogs. The general methodology may have parallels in the development of veterinary models to test putative therapies for other diseases of humans and animals.

Comparison of cell populations derived from canine olfactory bulb and olfactory mucosal cultures

OBJECTIVE

To evaluate the numbers and proportions of olfactory ensheathing cells (OECs) in cell cultures derived from the olfactory bulb (OB) and olfactory mucosa of dogs.

ANIMALS

7 dogs.

PROCEDURES

OB tissue and olfactory mucosa from the nasal cavity and frontal sinus were obtained from euthanatized dogs and prepared for cell culture. At 7, 14, and 21 days of culture in vitro, numbers and proportions of OECs, astrocytes, and fibroblasts were determined via immunocytochemistry. Antibody against the low-affinity nerve growth factor receptor p75 was used to identify OECs, antibody against glial fibrillary acidic protein was used to identify astrocytes, and antibody against fibronectin was used to identify fibroblasts.

RESULTS

Cultured OECs derived from the olfactory mucosa of the nasal cavity and frontal sinus had similar characteristics. However, whereas OECs in the OB cell cultures constituted approximately 50% of the cells at 7 days and approximately 75% at 21 days the proportion of OECs in cultures derived from both mucosal types was much lower, with approximately 40% OECs at 7 days and approximately 25% at 21 days. Analysis of OEC numbers revealed that these changes were accompanied by corresponding decreases and increases in the population of cells with fibronectin receptors.

CONCLUSIONS AND CLINICAL RELEVANCE

Although olfactory mucosal cell cultures yielded a sufficient number of OECs for spinal cord transplantation procedures in dogs, modification of culture conditions would be required to ensure that the derived cell population contained a sufficient proportion of OECs.

Autologous olfactory glial cell transplantation is reliable and safe in naturally occurring canine spinal cord injury

Intraspinal transplantation of olfactory glial cells (OGC) has produced well-defined beneficial effects in experimental rodent models of spinal cord injury (SCI) and therefore has considerable promise as a treatment for severe SCI in human patients. In this study, we used clinical canine cases of severe SCI to determine whether derivation and transplantation of OGC from an autologous source was feasible. From the nerve fiber layer of a single olfactory bulb, we were able to generate 5 x 10(6) cells from each patient within 3 weeks. Of this population, 72% were p75(+) OGC, 20% were meningeal cells, and the remainder mainly astrocytes. Intraspinal transplantation was not associated with any observable long- or short-term complications.

Behavioural analysis of the efficacy of treatments for injuries to the spinal cord in animals

There have been very few clinical trials evaluating therapies for naturally occurring spinal cord injury in dogs and cats. This review describes the methods suitable for evaluating the behavioural recovery of animals with spinal cord injuries, in either a clinical or a laboratory setting. A list of commonly used methods for evaluating behavioural recovery in animals is provided, both in the clinical and laboratory setting; the tests, their limitations and benefits and specific recommendations for their use are also discussed in more depth.

Cryopreserved cells isolated from the adult canine olfactory bulb are capable of extensive remyelination following transplantation into the adult rat CNS

Naturally occurring spinal cord injury in dogs provides a potentially powerful intermediate model for testing the efficacy of therapeutic strategies developed in experimental rodent models before phase 1 trials in human patients. A particularly promising strategy involves transplantation of olfactory ensheathing cells (OECs) that both promote axon regeneration and generate new myelin sheaths. As a first step in developing OEC transplantation in the canine intermediate model we describe the isolation, purification, and characterization of OECs from adult dog olfactory bulb. We also show that the canine OEC behaves in a manner similar to its rodent counterpart following transplantation into demyelinating lesions in rat spinal cord and that these properties are retained following cryopreservation.