It is well known and recognised that cell lines tend to undergo genotype and phenotype modifications along several passages. However we still purchase cell lines today from official repositories, that have originated from a donor over 50 years ago. We are not usually provided with any information from the supplier, regarding the number of times that vial has been passaged since the original cell donation, and scientists tend to start counting passages from when the cells have been purchased.

Is such a passage number really relevant, considering the unknown additional hundreds of times such a cell line must have been passaged over 50 years, to have been distributed to several repositories and sold to different customers?

I recently purchased a cell line from a reputable repository. The original cells were donated about 54 years ago. The vial I purchased had a label that said Passage Number 3 (without any plus sign prefix). This obviously does not include 54 years of passaging.

So my question is, is it really necessary to keep track of passage numbers on cell lines? If we need to keep track of genotype or phenotype changes, is it not better to consider the number of years that passed since original sample was donated, distributed and sold? Are there any opinions on this please?

I am specifically referring to cell lines here. Primary cells are a totally different story.

Thanks