(176f) Transplantation of 3D Human Mesenchymal Stem Cell Aggregates As Regeneration Centers for Ischemic Stroke Treatment

Transplantation
of 3D Human Mesenchymal Stem Cell Aggregates as Regeneration Centers
for Ischemic Stroke Treatment

Xuegang
Yuan¹, Shannon Helsper^1,2, F. Andrew Bagdasarian^1,2,
Jens T. Rosenberg^1,2, Teng Ma¹ and Samuel C.
Grant^1,2

¹Chemical & Biomedical Engineering; ²The National High Magnetic Field
Laboratory, FAMU-FSU College of Engineering, Florida State University,
Tallahassee FL

Abstract:

Human
mesenchymal stem cells (hMSC) have become a potential
candidate for cell therapy in stroke treatment due to their secretion of
trophic factors, immunomodulation and linage-specific differentiation.
 However, low cell survival and reduced therapeutic functions after
transplantation of 2D culture-expanded hMSC are the major barriers
limiting the clinical application of hMSC in
stroke patients [1].  Moreover, to meet scale-up requirements,
replicative expansion of hMSC demanded by
clinical use with conventional monolayer culture can result in cellular
senescence with reduced therapeutic efficacy.  To enhance hMSC therapeutic properties, precondition (such as
hypoxia) has shown promise in lesion and functional recovery for
the middle cerebral artery occlusion (MCAO) rat model.  In this
study, we report the impact of in vitro preconditioning
of hMSC via three-dimensional (3D)
aggregation culture. In the aggregation process, hMSC
spontaneously formed 3D aggregates and encapsulated a MRI-visible
micrometer-sized paramagnetic iron oxide (MPIO) on ultra-low adherent (ULA)
culture plates.  Instead of the implantation by intra-arterial (IA)
injection of single cell suspensions pursued previously, hMSC aggregates with
confined sizes and cell numbers were delivered directly by intraventricular
cerebral (IVC) injection for treatment of a MCAO stroke model in rats. The
influence of MPIO on hMSC aggregation process was
analyzed, as well as the aggregate-derived enhancement of
immunomodulatory, pro-angiogenic and anti-apoptotic cytokine secretion. To monitor the in vivo lifespan for
transplanted hMSC aggregates, serial magnetic resonance imaging (MRI)
at 21.1 T were performed to acquire images of aggregate placement,
distribution, longitudinal dissolution and potential stem cell migration within
the brain. Ischemic lesion recovery and functional behavior also were monitored.

Results
show that hMSC with MPIO particles are able to self-assembly into
aggregates with refined cell number and size.  hMSC aggregates retain
particles and required very low concentration of MPIO labeling to attain MR
contrast compared to 2D culture. hMSC within aggregates are smaller
in size, with increased CXCR4 expression and enhanced migration
through a caspase-mediated mechanism [2, 3].  By controlling the
compaction and cell number in hMSC aggregates,
cell metabolism and redox cycle were reconfigured and further activated the PI3K/Akt survival pathway, which contributes to the
resistance of ischemia and high level of reactive oxygen species (ROS) in
vitro [4].  MRI of the ischemic stroke lesion showed
increased ¹H and ²³Na signal as evidence of the
influx of extracellular water and disruption of ionic homeostasis. Lesion
volume analysis based on ²³Na MRI indicated increased recovery
for the hMSC aggregate group compared to
untreated stroke. Self-dissociation of delivered hMSC
aggregates was beyond the ventricular zone. Functional recovery was
evaluated by behavioral tests, with trends indicating lateral improvements with
implanted hMSC aggregates after MCAO over time. Together, the results
demonstrated that 3D aggregation of hMSC, even with
direct intact implantation, is an effective strategy that sustains the therapeutic
performance in stroke lesion recovery compared to standard adherent culture.

Reference:

1. Sart S., Tsai AC., Li Y., Ma T. Three-Dimensional Aggregates of
Mesenchymal Stem Cells: Cellular Mechanisms, Biological Properties, and
Applications. Tissue Eng Part B Rev. 2014;
20(5): 365-380.

2.
Tsai AC., Liu Y., Yuan X., Ma T. Compaction, Fusion, and Functional Activation
of Three-Dimensional Human Mesenchymal Stem Cell Aggregate. Tissue Eng Part A. 2015; 21(9-10): 1705-1719.

3. Liu
Y., Munoz N., Tsai AC., Logan TM., Ma T. Metabolic Reconfiguration Supports
Reacquisition of Primitive Phenotype in Human Mesenchymal Stem Cell
Aggregates. Stem Cells. 2016. 1549-4918.

4.
Yuan XG., Rosenberg J., Liu Y., Grant S., Ma T. Aggregation Preconditioning
Enhances Survival and Efficacy of Human Mesenchymal Stem Cells in Stroke
Treatment. Cytotherapy. 2019. In
review.