A Detailed Assessment of Varying Ejection Rate on Delivery Efficiency of Mesenchymal Stem Cells Using Narrow-Bore Needles

Abstract As the number of clinical trials exploring cell therapy rises, a thorough understanding of the limits of cell delivery is essential. We used an extensive toolset comprising various standard and multiplex assays for the assessment of cell delivery postejection. Primary human mesenchymal stem cell (hMSC) suspensions were drawn up into 100-µl Hamilton syringes with 30- and 34-gauge needles attached, before being ejected at rates ranging from 10 to 300 µl/minute. Effects of ejection rate, including changes in viability, apoptosis, senescence, and other key aspects of cellular health, were evaluated. Ejections at slower flow rates resulted in a lower percentage of the cell dose being delivered, and apoptosis measurements of samples ejected at 10 µl/minute were significantly higher than control samples. Immunophenotyping also revealed significant downregulation of CD105 expression in samples ejected at 10 µl/minute (p .05). Differentiation of ejected hMSCs was investigated using qualitative markers of adipogenesis, osteogenesis, and chondrogenesis, which revealed that slower ejection rates exerted a considerable effect upon the differentiation capacity of ejected cells, thereby possibly influencing the success of cell-based therapies. The findings of this study demonstrate that ejection rate has substantial impact on the percentage of cell dose delivered and cellular health postejection. Significance There are a growing number of clinical trials using mesenchymal stem cells (MSCs) for cellular therapy in a multitude of clinical targets. Numerous cell-therapy procedures use injection-based administration to deliver high-density cell preparations to the target site, either systemically or directly. However, there is growing evidence in the literature of a problem with cell injection methods in various cellular therapy applications. Because a thorough understanding of the limits of cell delivery is essential, an extensive toolset comprising various standard and multiplex assays was used for the assessment of cell delivery post-ejection. The effects of clinically relevant ejection rates and needles were assessed in terms of different aspects of cellular health of ejected human MSCs and their differentiation capacity. Our study emphasizes the potential impact of the administration protocol of cell suspensions and the importance of optimization of delivery parameters according to the nature and cellular responses of cells post-ejection. Our novel findings and comprehensive assessment of different parameters of cellular health and differentiation potential may be used to improve cell delivery using fine needles.