Rat Multipotent Mesenchymal Stromal Cells Lack Long-Distance Tropism to 3 Different Rat Glioma Models

BACKGROUND: Viral gene therapy of malignant brain tumors has been restricted by the limited vector distribution within the tumors. Multipotent mesenchymal stromal cells (MSCs) and other precursor cells have shown tropism for gliomas, and these cells are currently being explored as potential vehicles for gene delivery in glioma gene therapy. OBJECTIVE: To investigate MSC migration in detail after intratumoral and extratumoral implantation through syngeneic and orthotopic glioma models. METHODS: Adult rat bone marrow-derived MSCs were transduced to express enhanced green fluorescent protein and implanted either directly into or at a distance from rat gliomas. RESULTS: We found no evidence of long-distance MSC migration through the intact striatum toward syngeneic D74(RG2), N32, and N29 gliomas in the ipsilateral hemisphere or across the corpus callosum to gliomas located in the contralateral hemisphere. After intratumoral injection, MSCs migrated extensively, specifically within N32 gliomas. The MSCs did not proliferate within tumors, suggesting a low risk of malignant transformation of in vivo grafted cell vectors. Using a model for surgical glioma resection, we found that intratumorally grafted MSCs migrate efficiently within glioma remnants after partial surgical resection. CONCLUSION: The findings point to limitations for the use of MSCs as vectors in glioma gene therapy, although intratumoral MSC implantation provides a dense and tumor-specific vector distribution.