This study transplanted human neural progenitor cells labeled with different concentrations of ferumoxytol into the spinal cords of pigs to track the grafts over time using MRI. MRI visualized 100% of grafts labeled with the highest ferumoxytol concentration (400 μg/mL) up to 105 days post-transplantation. Stereological analysis found no significant difference in cell engraftment between labeling conditions, demonstrating ferumoxytol labeling allows long-term graft tracking without impacting engraftment. This technique can help monitor cell therapies in clinical trials.

1. CONTROL ID: 2223815
TITLE: Long-term MR tracking and stereological quantification of ferumoxytol labeled human neural progenitor cells
transplanted into the porcine spinal cord
AUTHORS (FIRST NAME, LAST NAME): Jason J. Lamanna
1, 2
, Juanmarco Gutierrez
1
, Lindsey N. Urquia
1
, Elman
Amador
1
, Thais Federici
1
, John N. Oshinski
3, 2
, Nicholas M. Boulis
1, 2
INSTITUTIONS (ALL):
1. Neurosurgery, Emory University, Atlanta, GA, United States.
2. Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States.
3. Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States.
PRESENTATION TYPE: Oral -General Abstract
CURRENT EMPHASIS: Preclinical in vivo Studies
CURRENT CATEGORY: Neurology
AWARDS: Student Travel Stipend|Young Investigator Award|Poster Award
ABSTRACT BODY:
Abstract Body: Transplantation of stem cells into the spinal cord has been explored for treatment of many diseases
(Feldman et al. Ann Neurol, 2014). The post-transplantation fate of cellular therapeutics is poorly understood in both
large animal models and the clinic because of limitations in cell graft detection. A minimally invasive technology for
cellular graft tracking to visualize grafts in vivo is needed. However, it is important that the diagnostic marker does not
impact the engraftment of transplanted cells. We propose to transplant ferumoxytol labeled human neural progenitor
cells into the spinal cord of a large animal, track the grafts in vivo with MRI, and quantify cell engraftment post-
mortem.
Human neural progenitor cells (Suzuki et al. PLoS One, 2007) were labeled with multiple concentrations of
ferumoxytol (0, 200, and 400 μg/mL). For each of the three labeling conditions ([0], [200], and [400]), four 250,000 cell
grafts (n=12 grafts/pig) were transplanted into the ventral horn of the thoracolumbar spinal cord of minipigs via direct
intraspinal microinjection. No post-operative deficits were observed and the pigs were maintained for 28 (n=3 pigs), 42
(n=3), and 105 days (n=5) after surgery. All [200] and [400] transplanted cell grafts (n=44 grafts/condition) were
visualized in vivo with a 3T full-body MR scanner using a T2*-weighted gradient echo sequence 14 days after
transplantation. 63.6% of grafts were determined to be on target in the ventral horn. The grafts were tracked with
serial MRI and quantified with a threshold method. The mean signal volume after transplantation was 0.4, 2.3, and
13.9 μL for [0], [200], and [400] grafts, respectively. Furthermore, 100% of [400] and 85% of [200] grafts were
identified in the 105-day cohort immediately prior to sacrifice with a mean volume of 0.5, 1.1, and 9.6 μL for [0], [200],
and [400] grafts, respectively.
The pigs were sacrificed and the spinal cords harvested. The cords were sectioned at 50 μm intervals and every 6
th
section immunostained for the human nucleus (HuNu). The engraftment of individual cell grafts was quantified using
unbiased stereology for the 42-day cohort. The engraftment was calculated for [0] (mean 24.0% cell engraftment,
range of 0.0-65.7%), [200] (17.1, 1.0-35.9), and [400] (25.0, 0.0-45.6) conditions and no statistically significant
difference was observed. Persistence of MR signal between 14 and 28 days for [200] and [400] grafts correlated with
graft survival (r = 0.47, p = 0.02) in the 42-day cohort. Stereology is ongoing for the other cohorts. Prussian Blue-
HuNu co-staining and transmission electron microscopy of tissue sections showed intracellular iron deposits.
Ferumoxytol labeling allows for immediate and long-term identification of cell grafts in vivo with MRI without impacting
cell engraftment in a large animal xenograft model. The ferumoxytol nanoparticles were observed in the cytoplasm of
transplanted, labeled cells. This approach can be used in ongoing and upcoming clinical trials to monitor cell-based
therapies. Furthermore, ferumoxytol labeling allows for immediate visualization of stem cells transplanted into the
spinal cord under MR-guidance.
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2. Disclosure Status
COI: Jason Lamanna: No COI to disclose. | Juanmarco Gutierrez: No COI to disclose. | Lindsey Urquia: No Answer. |
Elman Amador: No COI to disclose. | Thais Federici: No Answer. | John Oshinski: No COI to disclose. | Nicholas
Boulis: No Answer.