The concept "man" includes a great many variations, both in virtue of genetic nature (some disabled, others "gifted") and by nurture (natural variations in physical, intellectual, and emotional growth of humans ... "self made soul"...).
That a man has a heart rebuilt with stem cells, or a mechanical one, or a pig heart transplant, makes him no less a man.
Specific men have specific differing natural limits... which can and will be changed with treatment and manmade advances in health and biological intervention, but each will still be a man.
Be sure, I am not advocating that a machine masquerading as a person is a person just because it can imitate that person...
The extension of the limits on MAN, likely require changing his defunct cells with newly generated ones on a continual basis, etc. to grow generations of organs and cells and systems over and over, in an analogous way that new generations of people are newly made all the time, except it would take place within that person's own body, involve that persons own cells/DNA etc. and not entail or require replacement of the whole at the same time... but bits and pieces throughout over time.
The body already regenerates all of its cells every 7 years ... the problem is when this process creates unviable ones... telomeres (part of DNA) plays a role... so the system is there already... it just needs some support ..
an internal wheel chair of sorts.