Originally Posted by 2020
how could they grow COMPLETELY new follicles without existing stem cells in place?
Anyways, if that was true then this is bad news as you'll have thousands of new follicles in random patterns producing unevenly thin hair....
But the stem cells are in place, as we know from Cotsarelis's work. What's missing is the chemical signals to get them to differentiate into the hair-producing cells. It could be that these growth factors are a necessary part of the chain, but that doesn't mean they are capable of inducing follicular neogenesis by themselves.
Also, the Ziering quote may not necessarily indicate the creation of brand-new follicles, it may just mean that hair follicles that were completely dormant and not producing any hair were reactivated. So it would appear that there was a new follicle there. The problem is that unlike Replicel, Histogen aren't actually injecting cells that they can track down later. They are just injecting growth factors so it'll be a lot more difficult to tell whether a hair that suddenly sprouts comes from a brand-new follicle or just one that was dormant.
Replicel on the other hand can tell whether it's a new follicle or a rejuvenated one, because the cells they inject into mice glow green.