JangoCell Statement on Passage Number
Not all passages are created equal.
While passage number is the de facto metric used for determining cell proliferation capacity, the actual capacity is dependent upon the total number of cell divisions (or doubling number (PDN)) that a particular cell type can undergo. This can be illustrated with a simple example. Since stem cells are typically passaged upon reaching confluence, cells grown at low confluence in a flask or in a large vessel such as a bioreactor (large surface area to cell number) will require many more doublings to reach confluence before they are ‘passaged’ than cells seeded at high confluence. This can result in low passage numbers, but a cell population with more limited capacity for further cell division.
Due to different seeding and harvest densities, as well as the increased use of 3D systems for expansion of cell lines by commercial manufacturers, the number of population doublings per passage and the maximum population doublings achieved can vary significantly. Therefore, passage number is not the most reliable means of determining future cell proliferation capacity after purchase.
Supporting this, in 2022 Ivanovska, et al. stated, “different cell seeding densities, as well as intrinsic and extrinsic factors could influence cell proliferation” to the extent that reporting cell passage number may no longer be a useful metric. They suggest that in order to standardize the language around this process when reporting in the literature, “it would be more appropriate for the authors to report the population doubling level instead of the cell passage number.”
For these reasons, and to provide transparency concerning our cell products, JangoCell will express future cell division capacity, or the number of times that our cells will be able to divide and double in number after purchase (after thaw), in terms of population doubling number (PDN). We will express the current cell division number, or the number of times that our cells have already divided and doubled in number before cryopreservation, in terms of population doubling level (PDL). JangoCell’s primary stem cells when plated at ~20% confluency will display a PDN between 30-40 when cultured using the protocol recommended by JangoCell for each specific cell type.
Is passage number still the meaningful metric you are looking for?
Ivanovska A, Wang M, Eslami Arshaghi T, et al. Manufacturing mesenchymal stromal cells for the treatment of osteoarthritis in canine patients: challenges and recommendations. Frontiers in Veterinary Science. 2022; 9:897150. doi: 10.3389/fvets.2022.897150.