I think you'll feel comforted by knowing how they are made.  Since our own cells make these factors, they are completely natural.  To make a long story short, a certified young cell line is grown in petri dishes in the lab.  The cells line the bottom of the dish and a thin layer of liquid food called media  (like a soup) covers them.  As the cells grow, they secrete their own growth factors into the media. The media is harvested, purified and concentrated and put into a serum.  I hope this helps!  Dr. I