Scarless healing sub will tell you more about stem cells as they chase new articles.
Personally I do not see major improvements with them. I suppose some would show a % of improvement. It's like PRP a tool for healing / collagen production. Some Stem cells can do nothing as they do not target what you need specifically. They are extremely expensive here, I don't know about where you live.
The future will be targeted stem cells. As you know they will bind to customized receptors to do various actions.
Lots of wealthy ladies, Hollywood use them for facials and creams, ... Most of their improvements are under the knife. Be careful of the source apple stem fruit - stem cells and other dead forums are shit.
You could try it out once if you wish and see, prp has a similar % of improvement and is cheaper as s filler/ spacer.