Growth factors, peptides, and other macromolecules have become very popular in the cosmeceutical industry over the last decade (see blog on cosmeceuticals). Most of these cosmeceuticals are targeted toward females, however, there are a growing number of over-the-counter products (especially serums) that target men. Growth factors are normal signaling molecules that exist in all living cells of the human body, including skin cells. They can be contained and function within a cell or they can be secreted from the cell to have a direct effect on a neighboring cell. Growth factors orchestrate complex cellular processes including DNA repair, protein synthesis, and cell-to-cell communication (among thousands of other functions).
For example, a growth factor called transforming growth factor beta plays a major role in wound healing and collagen production in human skin cells. In terms of their application in skin care products, three classes of growth factors are currently on the market: plant-based, animal-based, and bioengineered. Plant-based growth factors vary widely, whereas animal-based growth factors are usually derived from the breast milk of nursing cows. Bioengineered growth factors are derived from cell culture produced in a lab. Since most growth factors are classified as proteins, they are quite large when compared to other molecules in the cell.
For example, when measured in molecular weight, transforming growth factor beta is hundreds of times larger than most molecules that can pass through the skin. In order for any molecule to have any effect on the skin’s structure or function, it must be able to penetrate the outermost layer of the skin and enter into the living component of the skin. This inner layer is where all of the action, like collagen formation, oxidative stress, and DNA repair, is taking place. When applied to the skin, growth factors are too large and complex to diffuse to the living skin tissue and produce an effect, such as to stimulate cell growth or accelerate DNA repair. So, although these growth factors may produce some effect when tested and directly applied to living cells in a petri dish, they simply don’t work on human skin because they don’t have access to the living tissue.
Dana Point Dermatology’s Bottom Line: Although growth factors sound good in theory when applied to the skin, they have very little effect on living skin cells because they are too large to penetrate the outer layer.
