Love most of your work, but in this specific case, actually your opening statement is incorrect.
Most cell lines do not show age related deterioration of function. Most life forms are single celled, and don’t display age related loss of function.
Everything alive today appears to be part of a continuum of life that is close to 4 billion years old.
So indefinite life appears to be the default, and age related loss of function seems to be a trick the multicelled organisms have evolved that have allowed for increased rates of evolving complexity.
So it seems that our cells are able to continue living indefinitely, but that those systems have been over-written.
The logic of this became clear to me as I completed my undergrad biochem studies in 1974.
Since then it became clear to me that we would work out how to stop aging, and that process would require 4 steps:
1/ Work out how to read DNA – and map the human genome (completed 2003),
2/ Software to model the shapes of RNA and proteins based on sequence and cytochemistry (some very powerful models emerging)
3/ Effective understanding of the various clocking mechanisms that produce age related loss of function in human cells (in process – at over 200 sites).
4/ design of effective countermeasures – see Calico, SENS, etc
The questions that have held my interest for the last 41 years are – what sort of social, political and technical institutions are required to effectively mitigate all other sources of risk and enable individuals to live a very long time with as much freedom as possible?
I’m not opposed to uploading in theory, and I do suspect that we are actually a lot more complex than many think, and that most of the cellular substructure of our brains does contribute significantly to who we are.