One of the things you just mentioned, bone loss being impossible, is called osteopetrosis which, although it's origins are complex, is specifically caused by gene expression changes and deterioration in your genome as you age.

You actually can treat DNA like a bodily coding langauge, as it is in fact the instruction manual that every process in your body works off of.

The only reason old cells are "old" is because they are being produced from a damaged, deteriorated, and incomplete genome.

Take puberty for example. The only reason puberty happens is because of the deterioration in a metabolic feedback loop that once broken kicks off the process of puberty through the newly unchecked increase in the production of GnRH in the hypothalamus.

Giving the body's cells fresh, undamaged DNA to work off of is like giving an unripped blueprint to a contractor. All of the parts that were once missing, like for instance stem cell production, are now back in the hands of the systems that build them and the processes that build those systems.

So even if the process may be more complex than currently understood, it's still well worth your while to get your genome sequenced as "insurance" for when full rejuvenation therapies do become viable.