The Effects of Placental Mesenchymal Stem Cells Labelled With Ultrasmall Superparamagnetic Iron Oxides on the Growth of Colorectal Cancer (CRC) Cells

Objective: To investigate the effects of human placental mesenchymal stem cells (PMSCs) labelled with ultrasmall superparamagnetic iron oxides (USPIOs) on the growth of colorectal cancer (CRC) cells and the feasibility of 3.0T MR in vivo tracer. Methods: PMSCs were labelled with USPIOs, the labeling efficiency was determined by Prussian blue-stained, and their biological characteristics were identified. A subcutaneous CRC HT-29 xenograft model in immunodeficient mice was established, and we attempted to consider the group was injected with labelled MSCs as experimental group. The growth and MR signal changes of xenograft tumors of nude mice was assessed, then, plot growth curve and analyzed the MR image quality in different sequences, obtained the pathological results after scan. Results: 1. USPIOs-labelled PMSCs had no significant influence on biological characteristics, such as cell viability, proliferation ability, and apoptosis rate ( P > 0.05). 2. The regions with low signal value could be observed in the experimental group on the first day on the MR. On the 7th day, the regions with low signal value were narrowed, and in some tumors showed poor clarity, whereas the signal values did not significantly change. The trend of growth of tumors in mice in the experimental group before injection of PMSCs was similar to that of the control group, while growth rate of tumor in the experimental group on day 5 after injection of PMSCs was slightly lower than that in the control group, and the volume of tumor on day 14 was noticeably smaller than that in the control group. There was no significant difference in the positive expression rates of CD31, CD34, and Ki67 between the two groups (P> 0.05). 3. The tracing ability of T2* mapping sequences for USPIOs-labelled cells was superior than T2WI and T2 mapping sequences. Conclusion: USPIOs-labelled PMSCs had high labeling efficiency, while cell viability, proliferation ability, and apoptotic rate were not markedly influenced. labelled cells injected into CRC transplanted tumors were studied for a long period of time, and only a certain inhibitory effect on growth of tumor volume was noted, while no meaningful influence on tumor proliferation and angiogenesis was found.