Cervical spinal cord therapeutics delivery: preclinical safety validation of a stabilized microinjection platform.
OBJECTIVE
The current series represents a preclinical safety validation study for direct parenchymal microinjection of cellular grafts into the ventral horn of the porcine cervical spinal cord.


METHODS
Twenty-four 30- to 40-kg female Yorkshire farm pigs immunosuppressed with cyclosporine underwent a cervical laminectomy and ventral horn human neural progenitor cell injection. Cell transplantation in groups 1 to 3 (n = 6 pigs each) was undertaken with the intent of assessing the safety of varied injection volumes: 10, 25, and 50 microL injected at 1, 2.5, and 5 microL/min, respectively. Groups 4 and 5 (n = 3 pigs each) received prolonged immunosuppressant pretreatment in an attempt to demonstrate graft viability. The latter was undertaken in an alternate species (mini-pig versus Yorkshire pig).


RESULTS
Neurological morbidity was observed in 1 animal and was attributable to the presence of a resolving epidural hematoma noted at necropsy. Although instances of ventral horn targeting were achieved in all injection groups with a coordinate-based approach, opportunities exist for improvement in accuracy and precision. A relationship between injection volume and graft site cross-sectional area suggested limited reflux. Only animals from group 5 achieved graft survival at a survival end point (t = 1 week).


CONCLUSIONS
This series demonstrated the functional safety of targeted ventral horn microinjection despite evidence for graft site immune rejection. Improvements in graft delivery may be augmented with an adapter to improve control of the cannula entry angle, intraoperative imaging, or larger graft volumes. Finally, demonstration of long-term graft viability in future preclinical toxicity studies may require tailored immunosuppressive therapies, an allograft construct, or tailored choice of host species.
Riley
Jonathan
J
Cleveland Clinic Foundation, The Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, USA.
Federici
Thais
T
Park
John
J
Suzuki
Masatoshi
M
Franz
Colin K
CK
Tork
Craig
C
McHugh
Jacalyn
J
Teng
Qingshan
Q
Svendsen
Clive
C
Boulis
Nicholas M
NM
D000818:Animals; D000870:Anterior Horn Cells / Q000166:cytology / Q000502:physiology / Q000637:transplantation; D002454:Cell Differentiation / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002574:Cervical Vertebrae / Q000033:anatomy & histology / Q000601:surgery; D005260:Female; D006084:Graft Rejection / Q000188:drug therapy / Q000517:prevention & control; D006085:Graft Survival / Q000502:physiology; D046748:Hematoma, Epidural, Spinal / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007260:Infusion Pumps; D007796:Laminectomy; D008845:Microinjections / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D055495:Neurogenesis / Q000502:physiology; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D013116:Spinal Cord / Q000166:cytology* / Q000502:physiology / Q000601:surgery*; D013118:Spinal Cord Diseases / Q000601:surgery*; D033581:Stem Cell Transplantation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D013234:Stem Cells / Q000166:cytology* / Q000502:physiology; D013238:Stereotaxic Techniques; D034421:Sus scrofa; D013594:Syringes / Q000009:adverse effects / Q000592:standards*; D014183:Transplantation, Heterologous / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D016896:Treatment Outcome
D007166:Immunosuppressive Agents