Table 2.

The 3 most common studies that tested various molecular probes to track stem cells in both normal and ischemic brain.

In vivo tracking using magnetic resonance imaging
Author	Target	Probe delivery method	Molecular probe	Location	Signal time	Findings
Zhang et al. 2016 [71]	Endogenous NSCs in vivo ischemic stroke adult rats	Stereotactic injection	Anti-CD15 antibody SPIONS	Intraventricular SVZ and RMS regions in adult mouse brain following MCAO	Detected day 1–day 8	(i) Proliferation of endogenous NSCs but no migration towards infarction lesion (ii) Findings may be due to short-term follow-up of only 8 days (iii) SPIONs have less imaging sensitivity than MPIOs (iv) Migration to OB along RMS observed after ischemic stroke (v) Introduction of heterologous antibody risk host immunological response (vi) Many other phenotypes undetected
Zhong et al. 2015 [73]	Endogenous NSCs in vivo normal adult rats	Stereotactic injection	Anti-CD15 antibody SPIONs	Intraventricular SVZ and RMS regions in adult mouse brain	Detected 1 day after injection, lasted 7 days total	(i) Small size, low artifact (ii) Increased specificity for NSCs (iii) Can track highly active areas such as OB surface binding less likely to affect biological behavior of cells (iv) Introduction of heterologous antibody risks host immunological response (v) Many other phenotypes undetected
Zhang et al. 2013 [79]	Exogenous neural progenitor cells in vivo ischemic stroke adult mice	Intravenous and implantation into hemisphere contralateral to stroke	Fluorescent mesoporous silica-coated superparamagnetic iron oxide nanoparticles	Right hemisphere following MCAO	Detected and analyzed 1–3 days after injection	(i) Cells injected both intracerebrally and intravenously could be seen migrating to ischemic sites of MCAO mice (ii) Migrated cells/cell clusters were detected nearby the lesion boundary (iii) Migrated cells reduced the MR signal intensity in ischemic region 3 days after injection