Well, this is all well and good, and I can’t say I disagree with any of your speculations, in principle. But, they are of little relevance to those of us looking to find near-term, near-immediate interventions to ameliorate specific age-related pathologies, and to try and meaningfully extend our lifespans now. You are dealing with an expert in envisioning the limits of the possible in biotechnology and medicine. I was one of the first two people to conceive of cell and tissue repair devices (1972):
And I have co-authored a Springer published book chapter on the future of critical care medicine: http://ift.tt/1Nl4ppQ
In 1988, I even tried my hand (with assistance from Steve Harris) at predicting the future of medicine in 2008: http://ift.tt/1DPYWzs it and weep, or laugh, as you will.
I’m dying right now and my concern with the ultimate possibilities and their likelihood in medicine is, as it properly should be, confined to the arena of cryonics. I’ve spent over 40 years in intense contemplation of not just possible future medical therapies, but of the detailed mechanics of how they might be realized. This has its uses, but staying alive right now isn’t one of them, again, except in the context of cryopreservation.
I am almost completely unconcerned that human kidneys show no propensity for the ability to regenerate nephrons. I have a good GFR for my age and plenty of nephrons. In fact, at my current rate of loss, my supply of nephrons will last till I’m about 130. However, currently my chances of living to be 130, which, BTW, is 60 years from now, are nil. If I look at the rate of decay of other vital organs in my body, I will very likely not survive till age 80. Factor in all my individual risks, and I’ll be lucky to make it to age 75 – very lucky. And that leaves out of consideration the quality of my life from now until it ends.
So, I don’t spend any time at all pondering whether nephrons in human kidneys can be regenerated, and unless you are doing specific research in this area, I would suggest that you not spend time on this, either – even if you personally are losing nephrons at a fierce rate and are headed for renal failure. This is because even if regeneration of nephrons had already been demonstrated in principle in mammals, it would never make it to clinical application by the time you needed it. You’d need a kidney transplant long before, and if you were smart, you’d be spending your time researching and thinking about how to get the optimum kidney you can, and then how to manage your immunomodulation post-transplant to hold onto it as long as possible. This presumes you’d already exhausted any therapeutic maneuvers to slow or halt your kidney disease.
This is in fact exactly what I did when I was 22 and discovered I was losing nephrons at a terminal rate. In my case, it was due to severe “essential” hypertension. I got a thorough work-up, selected the best meds available, and have continued to do that over the intervening 40 years – most recently switching my beta blocker to nebviolol. At diagnosis, my BP was 210/120. I’d have been dead decades ago if it were not for meticulous compliance with what was initially a complex regimen of medications (4x daily dosing)! The point here is that I didn’t give a thought to the “depressing reality” that nephrons don’t regenerate, but rather began to study hypertension.
Funnily enough, when people talk about life extending drugs, and when they ask me about what are the most effective drugs for life extension, my answer is the antihypertensives. These dugs have added more years, not to mention more quality years, to the average human lifespan than any other drug, or class of dugs that I know of: http://ift.tt/1DPYWzv
As you can see from the graph above, the incidence and prevalence of hypertension are so tightly associated with aging that hypertension might arguably be said to be one of the primary pathologies of aging.
I’m looking for interventions that will demonstrably slow aging now. But what I’m really looking for is treatments that will fundamentally impact aging itself, and that, in effect, means treatments that reverse aging, such as GDF-11, systemic fetal stem cells transplants, or both.