INTRANASAL DELIVERY OF MESENCHYMAL STEM CELLS TARGETS DIFFUSE INTRINSIC PONTINE GLIOMA IN MOUSE MODEL

Diffuse Intrinsic Pontine Glioma (DIPG) is a high-grade pediatric brainstem glioma afflicting children 7-9 years of age. The anatomic and diffuse characteristic of DIPG prevents surgical removal, while the blood-brain barrier prevents chemotherapeutic treatment. Radiation is currently the standard treatment but does not significantly improve survival. Intranasal administration of therapeutic stem cells has the potential to overcome these challenges and deliver anti-cancer treatments directly to DIPG. In order to assess the viability of intranasal delivery (IND) of mesenchymal stem cells (MSC) for targeting brainstem tumors, we have utilized a patient derived xenograft model of DIPG implanted in the brainstem in nude mice. Magnetic resonance imaging (MRI) was utilized for longitudinal tracing and quantification of superparamagnetic iron nanoparticle-labeled MSCs in the brain after IND. Our findings demonstrate that MSCs migrate along the trigeminal nerve towards the DIPG xenografts located in the brainstem. Tumors were detected with and without the use of gadolinium contrast agent prior to treatment using T1 and T2 weighted MRI sequences on a 7Tesla Bruker MRI. Pre-IND, whole brain images were acquired using a T2* weighted MR sequence in 3 dimensions with isotropic spatial resolution (150-micron). The same scan was repeated immediately following IND and at several later time-points (3h, 24h, 48h, and 120h post-IND). All brain images were realigned to allow accurate comparison between time points. Localized and diffuse hypointense MR signals, associated with the presence of iron nanoparticles used to label MSCs, were observed in the brainstem at multiple time-points following IND. The most concentrated hypointense signal was detected in the tumor region at 48 hours post-IND, suggesting that MSCs migrate to the tumor within 2 days. Images acquired at later time-points (5 days) revealed a more diffuse hypointense signal in the brainstem. Prussian Blue staining, used to detect the iron nanoparticles, identified and confirmed the presence of large concentrations of nanoparticles in the brainstem, particularly in the regions surrounding the tumor. Immunofluorescence, using antibodies specific for CD105, a marker for MSCs, and H3-K27M, a mutation specific for the implanted DIPG xenograft tumor, detected MSCs surrounding the tumor 5 days after IND. We also investigated how radiation affects the migration of MSCs toward the tumor. We found that repeated low doses of brainstem irradiation (0.5 Gy delivered 3 times a week for 2 weeks) significantly improved MSC migration and targeting of DIPG, as determined by MRI, Prussian Blue staining, and Immunofluorescence. Further studies are being performed to identify the mechanism of radiation-enhanced targeting of DIPG by MSCs. Our findings demonstrate the potential of non-invasive delivery of stem cell-based therapeutics against DIPG. Supported by the Robert H. Lurie Comprehensive Cancer Center.