Most skin-aging treatments work by prodding old fibroblasts and keratinocytes to accelerate the production of important cellular components. For example, retinoids act on retinoic acid receptors to activate collagen genes and deactivate collagenase genes. Glycolic acid, ascorbic acid, and certain growth factors stimulate synthesis of collagen by fibroblasts. Older fibroblasts and keratinocytes are sluggish for many reasons; they do not “hear” signals as well as younger cells do. Glycosaminoglycans such as heparan sulfate can help cells hear these signals. Heparan sulfate, for example, assists in the delivery of growth factors to cells, stabilizes them, and presents them to the receptors on the keratinocytes and fibroblasts, and amplifies cellular response to these factors.
A new angle in antiaging skin care is to create new keratinocytes rather than to stimulate old cells. For the last decade, personal care companies have touted the benefit of putting stem cells in cosmeceuticals, claiming that these cells would rejuvenate skin. However, this proved to be unsubstantiated marketing hype because the stem cells were plant derived (often from apples), had poor shelf life, and could not intercalate between the native skin cells and work with them to have any effect. Stems cells in cosmeceuticals became a point of disdain for savvy scientists.
A new approach to skin rejuvenation is to use agents to stimulate an individual’s own stem cells to form new, young cells. A stem cell known as leucine-rich repeat-containing G-protein–coupled receptor (LGR6+), present in the hair follicle, plays a very important role in the rekeratinization that occurs during wound healing. Recent studies have shown that stimulating the LGR6+ stem cell will result in “fresh” keratinocytes in the epidermis that will improve the skin’s appearance. At this point, we do not know if the LGR6+ stem cell has any effect on fibroblasts. The focus of this column is on the role of the peptide defensin in this process and its potential as a topically applied cosmeceutical ingredient to combat cutaneous aging.
Stem cells
Wounding the skin stimulates LGR6+ stem cells. This occurs when neutrophils in the immune system release defensins in response to injury, and, in turn, defensins activate LGR6+ stem cells. Situated above the follicular bulge, these cells are reported to have the capacity to synthesize all cutaneous cell lineages, including sebaceous gland and interfollicular epidermal cells.1,2 There are no specific studies that show that the LGR6+ cells generate new fibroblasts, but it seems likely. Transplantation of LGR6+ stem cells into the skin results in increased wound healing, hair follicle genesis, and angiogenesis.3 LGR6+ stem cells repopulate the epidermis by creating new basal stem cells. In regards to skin rejuvenation, it is clear that activated LGR6+ stems cells produce new, younger-acting keratinocytes in the epidermis.
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
Studying DefenAge
At this time, there is only one small multicenter, double-blind, placebo-controlled clinical study completed at three locations by investigators who are stockholders in the company and an independent dermatologic histopathologist who has no relation with the company; results have been reported in aesthetic dermatology industry newsletters. Each site had 15 patients for a total of 45 patients; all were women, aged 41-70 years (average age, 60 years), with little or no history of “quality” skin care. The study regimen used a system that contained alpha- and beta-defensins developed by Progenitor Biologics. Thirty patients used the three products in the DefenAge line: the 2-Minute Reveal Masque Exfoliator, 24/7 Barrier Balance Cream, and 8-in-1 BioSerum. The remaining patients received a three-part placebo system. Baseline biopsies were obtained to evaluate underlying conditions in the patients’ skin, and their skin was evaluated at 6 and 12 weeks, when additional biopsies were taken. Data analysis indicated that patients using DefenAge experienced significant improvement in coarse and fine wrinkles, pigmentation, pore prominence, epidermal thickness, as well as skin texture and evenness.
My personal opinion
I have never been a fan of formulations containing stem cells or peptides for the reasons listed above. DefenAge is unique in the way it has been stabilized, by penetrating the hair follicle rather than through the dermis and because defensin has very well-documented effects on the important LGR6+ stem cells. The effects of defensin on LGR6+ stem cells intrigue me. I do not intend to stop recommending retinoids for antiaging, but rather will add DefenAge to the antiaging regimen. In the past year, I have used DefenAge on many patients and have had many observations. I do not recommend starting retinoids and DefenAge at the same time because I have seen increased retinoid dermatitis. I suggest starting one the first month and then introducing the other product during the second month. Although no studies have been performed on this, my impression is that the DefenAge gives a quick result that helps improve patient compliance with the entire skin care regimen, but the effects reach a point at which no further improvement is seen. Combining DefenAge with a skin care regimen (targeted specifically to their Baumann Skin Type of course!) that includes a retinoid will increase efficacy. For wrinkle-prone skin types, I combine DefenAge with a retinoid, vitamin C, and heparan sulfate. After cleansing in the morning, I have them apply vitamin C followed by the DefenAge and an SPF. In the evening after cleansing, I have them apply a retinoid followed by a heparan sulfate analogue.
Conclusion
DefenAge offers a new approach to skin aging. At this time, there is much basic science research about the benefits of LGR6+ and that uses defensin to stimulate these stem cells; however, only one small clinical trial using defensin topically for antiaging has been published. It is doubtful that many studies will be performed because cosmetic companies are not allowed to make biologic claims so they have little incentive to demonstrate biologic changes. For this reason, we have to rely upon anecdotal reports from physicians such as the information that I have shared here.
Conflict of interest note: I have no financial relationship (no honorarium, stocks, or research funding) with Progenitor Biologics. I was asked to lecture in a DefenAge Symposium at the Vegas Cosmetic Surgery meeting but received no compensation. DefenAge products are sold through doctors, with my company, Skin Type Solutions Franchise Systems, as are heparan sulfate analogues, multiple brands of retinol, and 40 other product brands.
Dr. Baumann is a private practice dermatologist, researcher, author, and entrepreneur who practices in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote two textbooks: “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002) and “Cosmeceuticals and Cosmetic Ingredients” (New York: McGraw-Hill, 2014); she also authored a New York Times Best Seller for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). Dr. Baumann has received funding for advisory boards and/or clinical research trials from Allergan, Evolus, Galderma, and Revance Therapeutics. She is the founder and CEO of Skin Type Solutions Franchise Systems LLC.
References
1. Lough D et al. Plast Reconstr Surg. 2013 Nov;132(5):1159-71 .
2. Snippert HJ et al. Science. 2010 Mar 12;327(5971):1385-9 .
3. Lough DM et al. Plast Reconstr Surg. 2014 Mar;133(3):579-90 .
4. Kiatsurayanon C et al. J Invest Dermatol. 2014 Aug;134(8):2163-73 .
