The persistence of transient plasmids in cells after transfection can vary depending on multiple factors, including the cell type and the characteristics of the plasmid. In the case of bone marrow stem cells, the duration of transient plasmid expression can range from a few days to a few weeks.

Bone marrow stem cells are known to have a relatively short lifespan in culture, and their division rate can vary depending on the specific subtype of stem cells and culture conditions. Therefore, the duration of plasmid expression may be limited by the cell's proliferation and turnover rates.

Additionally, the choice of promoter in the plasmid can influence the duration of expression. Plasmids commonly used for transient transfection, such as pEGFP-N1, typically utilize strong constitutive promoters, like the CMV promoter, which can lead to robust protein expression shortly after transfection. However, the activity of the promoter may decline over time due to various factors, such as epigenetic modifications or dilution of the plasmid during cell division.

It's worth noting that transient plasmids are not maintained in the genome of the host cells. Therefore, if you need long-term or stable expression of your gene of interest in bone marrow stem cells, you may consider exploring alternative approaches such as viral vectors or gene editing techniques.

To assess the duration of transient plasmid expression in your specific bone marrow stem cell culture, you can monitor the expression of the transfected gene over time using techniques like fluorescence microscopy or flow cytometry. It is recommended to perform time-course experiments to observe the decay of expression and optimize the timing for downstream analyses or experiments based on your specific research goals.