Stem Cells International

Review Article

Potential Therapeutic Mechanisms and Tracking of Transplanted Stem Cells: Implications for Stroke Treatment

Table 1

Tracer agents currently available for tracking stem cells in stroke.


Tracer agent	Imaging modality	Labeled cell type	Route of administration	Results

Radiotracer
¹¹¹In oxine	SPECT	hUTC	IV	Approximately 1% of transplanted cells migrate to the site of injury, increasing vascular and synaptic densities in the IBZ [38]
Nanoparticles
SPIOs	3.0T MRI	MSCs	IA	Safe and feasible; ipsilateral MCA conditions and infarction volume affected the number of cells grafted [119]
	4.7T MRI	NSCs	IC	The majority of contralaterally grafted NSCs migrated to the peri-infarct area [76]
	MRI, BLI	hNSCs	IC	Tracking the fate and function of implanted cells in real time for 2 months [41]
MPIOs	MRI	eNSCs/NPCs	IC	Immediate, cell-independent MPIO accumulation at the site of injury [136]
	MRI	hMSCs	IC	Good label stability, did not affect hMSC viability [112]
FMNC	MRI	MSCs	IC	Safe and high efficiency for cell labeling, migration, and accumulation in the ischemic region [118]
fmSIO₄@SPIONs	3.0T MRI	NPCs	IC/IA	High MR sensitivity and cell labeling efficiency [117]
AIE NPs	FLI	BMSCs	IC	Low cytotoxicity and feasible [137]
GRMNBs	PA, 7.0T MRI, IVIS	MSCs	IV	Enhanced stem cell homing and reduced infarct volume, allowed short- and long-term monitoring [135]
MGIO	1.5T MRI	hfMSCs	IV	Low toxicity and feasible [138]
Gd-DTPA	MRI	BMSCs	IC	Safe and high efficiency [139]
Report gene
D-luciferin	BLI	BMSC	IP	Higher signal intensity of luciferase-expressing BMSCs 2 h after transplantation and migration to the IBZ [140]
Fluc and eGFP condition lentiviral vectors (Cre-Flex-LVs)	BLI, MRI	eNSCs	IC	A significant increase in eNSC proliferation and migration, and 21% of cells differentiated into astrocytes and neurons [134]
GFP and Luc2 double fusion reporter gene	BLI	ECFC	IA	Functional recovery, improved angiogenesis, neurogenesis, and increased apoptosis [133]

SPECT: single photon emission computed tomography; hUTC: human umbilical tissue-derived cells; IV: intravenous; IBZ: the ischemic boundary zone; SPIOs: superparamagnetic iron oxide; MRI: magnetic resonance imaging; MSCs: mesenchymal stem cells; IA: intra-arterial; MCA: middle cerebral artery; NSCs: endogenous neural stem cells; IC: intracerebral; BLI: bioluminescence imaging; hMSCs: human MSCs; MPIO: micron-sized superparamagnetic iron oxide; eNSCs: endogenous NSCs; NPS: neural progenitor cell; FMNC: fluorescent magnetite nano cluster; fmSIO₄@SPIONs: fluorescent mesoporous silica-coated superparamagnetic iron oxide nanoparticles; AIE NPs: fluorescent nanoparticles with aggregation-induced emission; FLI: fluorescent imaging; BMSCs: bone marrow-derived MSCs; GRMNBs: multigold nanorod (multiGNR) crystal-seeded magnetic mesoporous silica nanobeads; PAI: photoacoustic imaging; IVIS: interactive video information system; MGIO: microgel iron oxide; hfMSCs: human fetal MSCs; IP: intraperitoneal; Fluc: firefly luciferase; eGFP: enhanced green fluorescent protein; eNSCs: endogenous NSCs; ECFC: endothelial colony-forming cell.