Attila Chordash of Pimm thinks we can get further along in the healthy life extension path using just stem-cell based regenerative medicine than I do.
Systemic regenerative medicine is a coherent and inclusive engineering approach to eliminate all aging related problems indefinitely. Systemic regenerative medicine theoretically means the continuous, gradual and consecutive regeneration of every tissue and organ of the human body n times by combined regenerative medicine approaches, i.e. tissue engineering (in vitro grown organs and tissues implants or parts of them), systemic (via circulation) and locally targeted stem and progenitor cell transplantation, and endogenous stem cell niche activation with proper growth factor delivery aiming to maintain the physiological turnover and condition of the human body.
Which may be the case, and you never know for sure until the job is either done or failed. It seems to me I have the more defensible position, if somewhat less clearly articulated - but I'd be happy to proven wrong on this topic, given that the field of regenerative medicine is well on the way to become a behemoth to dwarf the cancer research community. No need for the years-long process of building up understanding, support, funding, institutes and enthusiasm - all those early days are behind us for regenerative medicine, tissue engineering and similar areas of research. Great and rapid progress lies ahead.
But, inconveniently, regeneration is not rejuvenation. Salamanders still grow old and die, as do the impressive mice of Ellen Heber-Katz. What Chordash is discussing is much more than assisted healing processes culled from the natural world, of course - it's more like the replacement scenario I touched upon a few days ago. Chordash sees this arriving sooner than I would predict:
Hypothetically, yes, pretty much everything except your brain is open to replacement just as soon as scientists can figure out how to build and install those replacements in a useful manner. That's a high bar, however. Your body isn't easily divided into piecemeal components; it's an overlapping bundle of interlinked, complex components - age-related damage to one system may make many related replacements useless or even counterproductive. Developing the technology base for safe replacement of the entire aging body is a long term project - not impossible, but certainly not something that you'll be seeing any time soon.
In order to make yourself physically younger, you must remove the molecular damage of aging within cells - either by replacing cells (such as entire stem cell populations) with less damaged cells, or by repairing that damage. Those are much the same thing if you want to replace cells with more of your own cells grown to order; you have to find a way to repair the damage of aging inside cells one way or another. You can't just regenerate - you must also rejuvenate by repairing this damage to cellular mechanisms.
Which is not to say that regeneration is worthless. The control of stem cells will drive an amazing series of advances in medicine, and quite possible provide the decade or two of additional healthy life that the system biologists think they can manage. There's great value and additional years in repairing broken hearts, blocking the source of cancer and doing everything else you can do at the level of cells.
But I don't see us progressing to a sufficient level of prowess in terms of replacing all systems in the body - and developing a strategy for the brain based upon cellular replacement and regeneration - to greatly extend the healthy human life span more rapidly than we can by following a path more like the Strategies for Engineered Negligible Senescence. The overwhelming question is not "is radical life extension possible?" Of course it is; the laws of physics and our understanding of biology are quite clear on that count. The question is whether we will live to see it - and I doubt that a technology base built only upon regenerative medicine and replacement can possibly advance fast enough and far enough for that.