Peptides
Defensin is a peptide. Peptides are short amino acid chains. These important substances are challenging to incorporate into topical formulations for various reasons, including stabilization difficulty, interaction with other molecules, and poor penetration (greater than 500 Dalton molecular weight). For these reasons, many peptide-containing formulations do not have efficacy. Attempts are underway to better develop or modify peptide products to enhance solubility, achieve better penetration, and target increased receptor activity. Defensins are peptides, which makes them difficult to formulate in a topical product. Special steps must be taken in the formulation process to stabilize defensin and allow penetration into the hair follicle where the LGR6+ cells reside. Fortunately, it is easier for a peptide to target the hair follicle because it can traverse through the “pore” – than it is to get a peptide to reach the fibroblasts in the dermis.
Defensins
Defensins, or human beta-defensins, are host defense peptides that exhibit antimicrobial activities against numerous bacteria.4 LGR6+ stem cells, which are dormant until they are activated to respond to damage, are stimulated by defensins. Defensins have been shown to stimulate keratinocyte proliferation, migration, and wound healing. (3) **Human alpha-defensin 5 peptide has also been shown to enhance wound healing, increasing LGR5+ and LGR6+ stem cell migration in the wound bed.(1)***
When formulated in a manner that allows for stability and penetration into the hair follicle where the LGR6+ stem cells reside, defensin formulations can be applied topically. A product sold as DefenAge uses a patented formulation that uses albumin, a large and stable protein, to stabilize defensin and act as a carrier molecule while helping the defensin maintain its integrity and extend shelf life in the serum base. The albumin/defensin complex is incorporated into liposomes to prevent other ingredients in the cosmetic base from interacting with the peptide and to enhance delivery to the LGR6+ target cell.
The role of defensins in treating skin aging
- Old fibroblast and keratinocytes are sluggish and lazy.
- Old cells do not “hear” signals as well as younger cells.
- LGR6+ stem cells repopulate the epidermis with new, young keratinocytes.
- Defensin stimulates LGR6+ stem cells.
- The defensin/LGR6+ pathway plays a role in keratinization.
- Using topical defensin can improve the skin’s appearance.