Advertising claims touting botulinum toxin like effects for topical moisturizers are becoming commonplace in print and television media. Sometimes I wonder if advertisers believe that if they say something loud enough for long enough consumers will begin to believe what they hear and see. Certainly, every dermatologist must have wondered for a moment if it is possible for any topical agent to function in a manner similar to injectable botulinum toxin. Why are these claims being made? What are the active agents in products claiming to induce facial muscle paralysis or relaxation? Are these products safe? How can these claims be made? This article will examine some of the issues surrounding the popularity of creams claiming botulinum toxin effects.
While this may seem surprising, no claims are being made regarding the botulinum toxin like effects of topical cosmeceuticals. The most famous of the topical botulinum toxin creams asks ad readers if their product is “Better than Botox?” This is not a claim. This is a question. It is left up to the consumer to answer the question. Of course, the answer is “no.” However, the consumer interest generated by this ad has been extremely successful, to the point that numerous cosmeceutical manufacturers are using the word Botox in creative ways in advertising.
Imagine that you are a cosmetic manufacturer. Imagine that you want to appear to be novel, cutting edge, innovative, and state-of-the-art. What would you do? Well, you would latch on to the image associated with anything successful that was expensive and performed by a dermatologist. After all, dermatologists are reputable physicians and have done extensive research to demonstrate the safety and efficacy of botulinum toxin injections. Why not latch onto this successful aura and somehow transfer this image of respectability and cutting edge technology to your newest addition to your product line? Even if your product could not possibly function as well as botulinum toxin, it is worthwhile rubbing shoulders with a successful cosmetic procedure.
The most common active agents in cosmeceuticals claiming to have botulinum toxin like effects are engineered peptides. Several of them have been commercialized and introduced into the prestige and mass market. One of the most interesting peptides is known commercially as argireline. It is a hexapeptide composed of 6 amino acids with the INCI name of acetyl hexapeptide-3. Since peptides are considered foods, they can be readily added to a variety of cosmetics without worry of undergoing FDA scrutiny. Argireline is sold as a 0.05% powder that can be easily added to moisturizer formulations immediately prior to packaging, due to its inherent heat instability. The raw material costs $25 for 50 ml, which is rather pricey for a cosmetic active.
Argireline structurally mimics the SNAP-25 protein, which is part of the SNARE complex at the neuromuscular junction. Thus, it is able to destabilize the SNARE complex that is broken through the injection botulinum toxin. Breaking the SNARE complex results in muscle paralysis while destabilization results in muscle relaxation. Thus, Argireline is advertised as extending and potentiating the effect of botulinum toxin. Is it able to accomplish this feat? Probably not. Even botulinum toxin cannot induce facial muscle paralysis when applied topically. Reaching the SNARE complex for practical purposes requires injection of materials through the skin.
Once one gets through the cosmetic hype, it is actually rather frightening to think what might happen if topical agents could indeed modulate neuromuscular function. This would then mean that casual contact with environmental proteins might result in temporary muscle paralysis that could be dangerous. I personally am glad that the design of the human body prevents topical proteins from reaching the neuromuscular junction.
Probably the most popular peptide that is used in moisturizers comparing efficacy to botulinum toxin, such as Regenerist or Strivectin, is commercially known as Matrixyl. Matrixyl is a pentapeptide composed of the 5 amino acids lysine, threonine, threonine, lysine, serine. It is abbreviated as KTTKS.
As I mentioned previously, it is almost impossible to get large protein fragments to penetrate into the skin. Pentapeptides can enter the skin if linked to a penetration enhancer, such as palmitic acid. Thus, KTTKS was linked to palmitic acid to create Pal-KTTKS, which is the chemical composition of Matrixyl. Matrixyl has no effect on the neuromuscular junction, but it is thought to be a modulator of collagen breakdown.
It is known that Matrixyl is a fragment of collagen type I and is thought to function by flooding the cell with excessive collagen breakdown fragments. This abundance of collagen breakdown products is thought to alert the cell to excessive cellular damage and downregulate the synthesis of collagenase. If collagenase is downregulated, then collagen production should theorectically increase. Typically Matrixyl is used in concentrations of 4 parts per million, thus functioning as a cellular messenger to modulate functioning.
Currently advertised products that contain Matrixyl draw comparisons to botulinum toxin, but do not claim to have any botulinum toxin like effects. They instruct the consumer to try their product as a “less drastic” alternative to botulinum toxin or other cosmetic surgical procedures.
The search for topical agents that might be safe curare-like chemicals has intensified amid the tremendous popularity of botulinum toxin. One botanical active finding its way into muscle modulating creams is commercially known as Myoxinol. Myoxinol is an oligopeptide obtained from Hibiscus seeds with an INCI name of Hydrolyzed Hibiscus Esculentus Extract and Dextrin. It is a fine beige to yellow powder that is classified as a food. It is used in cosmetics in concentrations ranging from 0.5-2%.
The muscle relaxation effects of this botanical are based on observations resulting from the incubation of striated muscle fibers with Myoxinol. It was noted that spontaneous muscle contractions decreased 1, 2, 6, and 24 hours following the presence of Myoxinol in the muscle fiber culture. This decrease in spontaneous muscle contractions was interpreted to mean that the chemical decreased muscle tone and would therefore induce facial muscle relaxation, which in turn might enhance or extend the effect of botulinum toxin. Again, there are many suppositions made as to the efficacy of Myoxinol and no direct comparisons to botulinum toxin are made.
All of the peptides and botanicals discussed are considered safe by the FDA, since they are classified as foods. I would not be concerned for the safety of patients that wish to give these novel cosmeceuticals a try. These products are basically moisturizers that desperately want to be something more than an oil-in-water emulsion. They may indeed improve the texture and feel of the skin while decreasing the appearance of fine facial lines due to dehydration.
It is my current understanding that the NAD is looking into these claims. There is concern that comparing an injectable drug to a cosmetic moisturizer is like comparing apples to oranges. While it is not illegal to make the comparison, it may be misleading to the consumer to mention such dissimilar products in the same sentence. I think dermatologists would certainly agree that this is the case. It will be interesting to see how companies will alter their advertisements in the future.
The tremendous efficacy and popularity of injectable botulinum toxin for the diminution of wrinkles has certainly raised the bar for the cosmetic industry regarding anti-aging formulations. The future will certainly find more products on the market hoping to be the next best thing to botulinum toxin.
Have you ever wondered how new cosmeceuticals are developed? Do you ever find yourself asking how in the world they came up with this stuff? Do you wonder how they know it works? Do you wonder if the cosmeceutical is safe for your patients? Do you wonder how it can remain on the market if it doesn't appear to work? These are all excellent questions. Questions that I too had until I had the opportunity to work on the development of several cosmeceutical formulations from concept to market. Perhaps exploring the development process will shed light on why the cosmeceutical marketplace exists as it does in the United States.
Cosmeceuticals are an undefined, unregulated category of over-the-counter (OTC) products designed to do more than adorn the skin, but without the medical benefits of prescription drugs. Around the world, the cosmeceutical category is being redefined. For example, in Japan cosmeceuticals are called "quasi-drugs" based on their ability to alter the structure and function of the skin with ingredients that are not classified as drugs. It is unlikely that a better definition of cosmeceuticals with be forthcoming in the United States, which is hampering research and development in this area.
Cosmeceuticals are formulated typically as moisturizers. Moisturizers are designed to be part of the maintenance regimen of skin care preventing transepidermal water loss, soothing itching skin, and providing a smooth, soft feel to the skin surface. Bland moisturizers were the majority of the cosmeceuticals in the marketplace for many years until the consumer began to demand more technologically sophisticated products. The revolution in modern cosmeceuticals really began with the introduction of glycolic acid into the marketplace, which produced a visible effect through the induction of exfoliation. This single ingredient opened the door for products that delivered more than just moisturization benefits.
The new push in cosmeceutical products is to develop formulations that prevent and reverse the signs of aging skin. The bulk of the prevention is accomplished through the addition of sunscreens to moisturizers providing evidence for an antiaging claim through UV protection. But, protection is not enough. Consumers want the additional benefit of reversing the signs of aging. The introduction of new cutaneous aging theories related to oxidation induced skin inflammation has created renewed interest in the search for antioxidant, anti-inflammatory cosmeceutical ingredients. This has led to the plethora of antioxidant containing and anti-inflammatory containing moisturizer formulations.
The easiest source of new cosmeceutical ingredients is the plant kingdom. Plants are rich in endogenous antioxidants, since they must survive in an environment rich in UV insults. Plant extracts are also felt to be safe and meet the FDA criteria for substances that can be put in OTC formulations. It is generally felt that substances that are safe for oral consumption can be assumed safe when applied topically. This has led to a renewed interest in herbal preparations and homeopathic treatments.
The search for botanicals has led to the gathering of flowers, seeds, roots, leaves, twigs, and berries from plants all over the world. It important to remember, however, that the constituents of a plant component are influenced by the season in which the plant material was picked, the growing conditions, and the processing of the agent. These variables are summarized in Table 1.
The currently popular cosmeceutical antioxidants are soy, curcumin, silymarin, and pycnogenol. These are all plant derived. Soy comes from the soybean, curcumin comes from the tumeric spice used in Middle Eastern cooking to impart a yellow color to food, and pycnogenol comes from pine bark. Plants contain antioxidants in the form of flavones, xanthones, carotenoids, and polyphenols. These plant extracts are typically identified via mass spectroscopy and synthesized to create a less expensive additive with greater consistency.
Botanical antioxidants function no differently than any other type of antioxidant. The botanicals contain chemicals, such as the flavinoids, carotenoids, and polyphenols mentioned earlier, that are able to donate an electron to an unstable oxygen species. Any substance with a free electron can function as an antioxidant, which is why so many antioxidant type substances have been identified.
The newest botanical anti-inflammatories are gingko biloba and green tea. Both of these botanical anti-inflammatories function by down regulating key processes in the inflammatory cascade. Notice that the active agent is again the polyphenol and flavinoid fraction of the plant. This is due to the fact that all antioxidants are by definition anti-inflammatories, since oxidative insults activate the inflammatory cascade. Thus, for all practical purposes cosmeceutical anti-inflammatories and antioxidants should be considered one in the same. The main difference is in the claims associated with the botanical ingredient.
There are a variety of botanicals that are incorporated into products designed for sensitive skin. These substances are known as anti-irritants. You might say that antioxidants and anti-inflammatories are also anti-irritants and this perspective would be correct, but there are certain ingredients that seem to be associated with the anti-irritant claim. It is interesting to analyze how these ingredients function. Both prickley pear and aloe vera are mucilages placing a protective film over the damaged skin surface. This is only effective, however, if the juice is freshly extracted from the plant. Since this is not possible in cosmeceutical formulations, another mechanism of action must be operative. In the case of aloe vera, it is important to recognize that this plant extract is high in choline salicylate, a well-known medicinal anti-inflammatory. Allantoin also decreases white blood cell infiltrates in the skin. Most botanical extracts have some explanation for their purported effect that is completely consistent with accepted medical principles.
New cosmeceuticals are identified based on the algorithm presented in Table 5. Once the botanical active is identified and synthesized it is typically applied to a fibroblast gene chip to determine if it affects any key cellular event. After demonstration of a presumed physiologic effect, the active is tested in vitro to determine an effect on cultured fibroblasts. If positive data is obtained, the active is studied in a mouse model for confirmation. The active is then placed in a vehicle suitable for human application and clinical studies are undertaken. Successful human clinical studies pave the way for successful introduction into the marketplace via ingredient licensing arrangements.
Most quality cosmeceuticals are formulated from ingredients that already have a proven safety record in the marketplace. This may be due to their extraction from foods, such as topical lycopene from tomatoes or topical avocadin from avocados. Or, extensive animal testing may be undertaken by the raw material supplier to determine that the single ingredient is appropriate for human use. In the case of botanicals, most are assumed safe based on their ubiquitous nature. Efficacy is much harder to validate. Typically, human clinical testing is undertaken under the direction of a research laboratory or a dermatologist with defined parameters to substantiate efficacy. The efficacy is tested usually only on the final formulation making it difficult to separate the efficacy of any individual active. Well-controlled studies utilize a vehicle compared to the vehicle plus the active to isolate the effect of the unique ingredient. However, there are no standards for cosmeceutical testing in the industry.
Cosmeceuticals form an important part of the OTC skin treatment market. There are some industry forecasters who feel that the cosmetics industry has hit a glass ceiling in new cosmeceutical development largely due to the failure of the FDA to develop a new classification system. It is thought that a new "quasi-drug" category, similar to the Japanese designation, would allow the introduction of more robust active ingredients into cosmeceuticals. These more robust ingredients would provide enhanced consumer perceived skin benefits supporting stronger claims. The consumer may wonder why cosmeceuticals are not more thoroughly studied and tested. This is in part due to the fact that it may be in the manufacturer's best interest not to fully understand exactly what a cosmeceutical active can accomplish. Cosmeceuticals that function too well would alter the structure and function of the skin and become drugs. The current state of the cosmeceutical marketplace is not due to the industry lack of desire to perform thoughtful research and develop quality products, but rather due to limitations imposed by the present regulatory climate.
There are a myriad of new active ingredients entering the marketplace, each one claiming to be more efficacious than prior raw materials. There are vitamins and supplements and botanicals and serums and skin tighteners and anti-inflammatories and collagen rebuilders and muscle modulators and moisturizing factors and skin conditioners and elastin modifiers and antioxidants and metabolic regulators and hair strengtheners and etc., etc., etc. While the rapidity with which ingredients enter and leave the cosmetic counter may seem bewildering to the dermatologist, there are some actives that have remained in cosmetic and skin care formulations for many years. One group of actives that have enjoyed tremendous longevity are proteins and their derivatives. Why are proteins so popular? Simple. They provide a tremendous variety of functions important to moisturizers, antiaging cosmeceuticals, and hair conditioners. This article follows the history of proteins in skin and hair care products by initially examining some of the older protein actives still important in current formulations and following the progress that has led to the newer biologically active peptides.
Some of the earliest cosmetics were actually moisturizers designed to prevent dry skin. These moisturizers were produced by boiling cow skin to extract the gelatins and proteins that were used primarily for their ability to thicken and add body to early creams. It was not recognized for many years that proteins had skin effects beyond their ability to improve product viscosity.
Proteins are actually extremely effective humectants. Humectants are substances that are able to bind water. Other humectants include glycerin, propylene glycol, and sorbitol. However, protein is a unique humectant among this group in that it is able to bind and hold water longer and to a greater degree. An excellent example of the humectant ability of protein is the changes that a callus undergoes when it is soaked prior to paring. Initially, the callused tissue is yellow, firm, and inelastic. Soaking the callus in water for 15 minutes changes the compacted keratin from yellow to white and softens the tissue so that it becomes flexible and can be easily pared. Proteins in moisturizers function much the same way.
Proteins are added to moisturizers to increase amount of water present in the stratum corneum and the viable epidermis. This enhanced water content decrease wrinkles of dehydration and creates a moist environment optimal for barrier repair. Thus, proteins function both as cosmeceuticals and viscosity agents in skin moisturizers.
Proteins have also been recognized for their value in hair care, where they function as a moisturizer for the hair. They have been incorporated into hair conditioners of the instant type, which are applied following shampooing and immediately rinsed, and deep conditioners designed to be left on wet hair for 30 minutes prior to removal. Protein-containing conditioners are important to restore the cosmetic value and strength of hair that has been damaged to the removal of the cuticular scales, a process known as weathering. As hair weathers, it looses its strength due to removal of the cuticular scales and damage to the underlying cortex. This damage creates areas where the hair shaft contains holes, through which protein present in hair conditioners can enter the hair shaft. Even though only small amounts of protein can enter via this route, the end result is an increase in hair shaft fracture strength by up to 10%. Usually, the protein must be hydrolyzed to a particle size of molecular weight 1000 to 10,000 to enter the hair shaft., The protein diffusion is reversible, however. This means that any exogenous protein present in the hair shaft will be removed at the time of shampooing, necessitating reapplication of the protein-containing conditioner.
The proteins can also function to neutralize the charge from static electricity that may be present on the hair shafts. This ability to quench static electricity increases the manageability of the hair and improves styling ease.
As knowledge was accumulating regarding the physiology of skin and hair moisturization, it was recognized that proteins play another important role. Cosmetic chemists had searched for years for the skin's own natural moisturizer. After several years of experimentation, it was determined that the combination of the ingredients listed in Table 1 form the recipe for the endogenous moisturizer responsible for maintaining cutaneous hydration. Notice that the recipe contains both amino acids and peptides. The natural moisturizing factor was one of the earliest uses of peptides in the cosmetic industry.
As cosmetic science has evolved, more and more complex uses for peptides, which form the building blocks of proteins, have appeared. One cosmeceutical use of peptides is as a carrier for larger molecular weight molecules to enhance penetration. For example, copper, a known cofactor in the production of collagen during wound healing, was linked to a peptide to enhance penetration in the wounded skin. This copper peptide technology was then adapted to general skin care as an antiaging moisturizer in both the physician dispensed and mass markets.
Probably the newest use of peptides are as regulators of cellular function. Since the body uses peptides to communicate between cells, it was theorized that perhaps engineered peptides might be able to up regulate or down regulate cutaneous functions that had decayed with time due to the cumulative effects of aging. This theory was investigated more thoroughly by chemists under the direction of Dr. Karl Lintner at Sederma in France. They developed a variety of peptides and tested them in cell culture to determine their biologic effects. The most interesting peptide was found to be a pentapeptide composed of lysine, threonine, threonine, lysine, serine. This pentapeptide is abbreviated as KTTKS.
One of the challenges of peptide chemistry is to achieve penetration into the skin. This is essential if the peptide is to exert cellular effects. In order to enhance penetration, the KTTKS peptide was linked to palmitic acid. Thus, the commercialized pentapeptide is termed Pal-KTTKS with the trade name Matrixyl. Matrixyl contains 800 parts per million of Pal-KTTKS, which is typically used at a concentration of 1-4 parts per million in currently marketed cosmeceutical moisturizers.
The activity of Pal-KTTKS was documented through several studies. The first evaluation was undertaken in cultured lung fibroblasts where it was shown to stimulate cellular growth and increase both collagen and fibronectin synthesis. The next studies were performed on fibroblasts from a 63 year old donor. Here the efficacy of Pal-KTTKS was compared to TGF beta for its ability to increase collagen type IV synthesis. In addition to increasing the production of collagen type IV in cultured fibroblasts, it was also found to increase collagen type I synthesis. Lastly, Pal-KTTKS was shown to increase the production of glycosaminoglycans by human skin fibroblasts obtained from a 30 year old donor.
The antiaging effects of Pal-KTTKS have been compared to those of tretinoin, since both increase collagen production thereby reducing some of the cumulative effects of photoaging. Typically, Pal-KTTKS is used in combination with other active ingredients that also impart moisturzation and other skin benefits. For example, a currently marketed product with 3 parts per million of Matrixyl also contains panthenol as a humectant, niacinamide as an enhancer of cell turnover, vitamin E as a skin soothing agent, allantoin as an anti-inflammatory, and 4 green tea polyphenols to function as cutaneous antioxidants (Regenerist, Olay, Procter & Gamble). Thus, all the ingredients work together to create a modern cosmeceutical moisturizer.
The exact mechanism of action of Pal-KTTKS has not been fully elucidated, but it is known that this pentapeptide is a fragment of collagen type I. Many different fragments of collagen type I were studied, but Pal-KTTKS performed the best, as demonstrated by the cell culture work previously presented. It is thought that the exposure of the fibroblasts to high levels of collagen type I breakdown products triggers a cellular recognition that too much collagen has been destroyed. This in turn down regulates the activity of collagenase resulting in less collagen destruction and enhanced collagen synthesis. Further research is ongoing in this area.
The pentapeptides are the first of the modern protein derivatives designed to alter cellular functioning. Restoring youthful cellular communication is an enticing model to reverse the cell senescence that results from messages that are either not received or improperly received. Certainly, there will be advances made in peptide technology as our ability to measure the effects of the new biologics progresses.
Proteins are the most allergenic substances when placed on the skin. For this reason, cosmetics avoided the use of proteins for many years. Probably the first protein used on the skin was hydrolyzed collagen derived from the heating of bovine skin. This protein was added to hair conditioners and skin moisturizers for its ability to function as a humectant to hold water. The use of hydrolyzed collagen revolutionized skin care and hair care in the 1980s. More recently, with advancements in protein chemistry, engineered molecules can be created that mimic functioning structures within the body. Since proteins are too big to penetrate the skin barrier, engineering peptides made of carefully selected amino acids are synthesized that have the potential to enter the stratum corneum and theoretically affect epidermal and dermal functioning.
Peptides are the cellular messengers of the body allowing the modulation of receptors, activating enzyme release, and regulating the production of proteins. Peptides are present in many of the new generation cosmeceuticals. They are considered safe when topically applied, since peptides are ingested on a regular basis when consuming meat. Allergic reactions to cosmetic topical peptide formulations have not been reported to date, thus increased use of peptide technology in moisturizers is expected in the future. This article examines the peptides families that are currently is use and looks at specific peptides as examples of each family.
Peptides are formed from amino acids that are selected by the protein chemist to achieve a specific functional goal. The peptide families that have been presently identified are listed in Table 1. The first peptides introduced into the wound healing marketplace were carrier peptides, which were then adapted to the anti-aging skin care market. From the carrier peptides, the next development was signal peptides designed to mimic a natural body structure and turn on or off production of an endogenous protein. Neurotransmitter peptides were then developed that interrupted acetylcholine release. Finally, enzyme modulating peptides directly or indirectly inhibit enzyme functioning were produced. Our discussion now turns to discussing specific examples of each of these peptide families that is in presently marketed cosmeceutical preparations.
The first commercialized peptides were carrier peptides. These peptides were designed to hook to another ingredient and facilitate transportation of the agent to the active site. The first carrier peptide was designed to deliver copper, a trace element necessary for wound healing. From a wound healing application, a peptide known as GHK-Cu was commercialized into a line of skin care products to minimize the appearance of fine lines and wrinkles (Neutrogena, J&J). GHK-Cu is composed of glycine and histidyl and lysine hooked to copper and was found to induce dermal keratinocytes proliferation. GHK was originally isolated from human plasma and then synthetically engineered.
The largest peptide family currently used in marketed cosmeceuticals is the signal peptides. Signal peptides stimulate collagen, elastin, fibronectin, proteoglycan, and glycosaminoglycan production creating the appearance of younger looking skin. The most popular signal peptide is palmitoyl pentapeptide, commercially known as Matrixyl (Olay Regenerist, P&G). Palmitoyl pentapeptide, abbreviated Pal-KTTKS, is composed of the amino acids lysine, threonine, threonine, lysine, and serine. It is a procollagen I fragment demonstrated to stimulate the production of collagen I, III, and IV in vitro. It is used in a low concentration of 4 parts per million, since it theoretically acts as a “signal” whereby one molecule has a cascading effect. The idea is to present the body with procollagen fragments that will down-regulate the production of collagenase thereby increasing dermal collagen and minimizing the appearance of aging.
Neurotransmitter peptides function by inhibiting the release of acetylcholine at the neuromuscular junction. They are similar to botulinum toxin in that both selectively modulate synaptosome-associated protein of 25,000 Daltons, more commonly known as SNAP-25. Botulinum toxin A proteolytically degrades SNAP-25 while acetyl hexapeptide-3, a neurotransmitter peptide, mimics the N-terminal end of the SNAP-25 protein that inhibits the SNARE (soluble N-ethyl-maleimide-sensitive factor attachment protein receptor) complex formation. Acetyl hexapeptide-3 is commercially known as Argireline (Centerchem). It supposedly functions topically to relax muscles, much like a weak short-lived botulinum toxin, by inhibiting vesicle docking through prevention of the SNARE complex formation. This muscle relaxation reduces the appearance of facial wrinkles.
A second commercialized neurotransmitter peptide is pentapeptide-3, commercially known as Vialox (Centerchem). Pentapeptide-3 is a competitive antagonist at the acetylcholine receptor. It also reduces muscle contraction and theoretically the depth of wrinkles on the face.
Enzyme modulating peptides directly or indirectly inhibit the function of a key enzyme in some metabolic process. Many of these enzyme modulating peptides are extracted from botanical sources rather than engineered through protein chemistry. Soy proteins, already used in cosmeceuticals for the reduction of pigmentation and the inhibition of hair growth, possess another peptide that inhibits the formation of proteases. Rice proteins possess a peptide inhibits MMP (matrix metalloproteinase) activity. These naturally occurring peptides are used in cosmeceutical facial moisturizers in combination with the previously discussed synthesized peptides.
Peptides can be perplexing to the uneducated dermatologist, but once it is understood that they are naturally occurring or synthetic biologically designed combinations of amino acids, the puzzle come unraveled. The intent of the peptide chemist is to influence cellular communication by exposing the skin to mimics of naturally occurring amino acid sequences. While the effect of peptides can be easily demonstrated in Petri dish cultures of fibroblasts or muscle cells, it is much harder to assess the cosmeceutical value of topical peptides for human facial application. Almost all peptide formulations contain a mixture of robust moisturizing ingredients. It can be hard to determine whether the improvement in skin smoothness and reduction in facial wrinkles is due to the moisturizing abilities of the formulation or the addition of the peptide. In some regards, since cosmeceutical is a fancy name for cosmetics, as long as the consumer is pleased with the effect of the facial cream and purchases another container, the product is a success.
In dermatology, we want to link cause and effect to a specific ingredient. Indeed this should be our quest as skin scientists. However, double blind placebo controlled studies are hard to conduct in the moisturizer realm because the vehicle formulation without the peptide may still produce skin improvement. This is why many cosmeceutical moisturizer tests are performed against the current market leader as a control. The goal is to show that the new peptide-containing finished formulation performs better than a presently marketed cream. Indeed the peptide-containing moisturizer may be better, but the superiority cannot be totally attributed to the peptide alone. This is a key distinguishing characteristic of the cosmetic realm from the drug realm.
It is important to recognize that peptide chemistry is yet in its infancy. Peptides hold the promise to modulate much of the functioning of the skin, but the details remain perplexing. This article has unraveled some of the confusion regarding peptides by organizing them into families and presenting examples of peptides in current use. The dermatologist should closely watch this family of cosmeceutical ingredients as their true potential has not yet been fully realized.
Vitamin A is of primary importance to the survival of human and plant life in an evironment rich in oxygen. Vitamin A, and its precursor beta-carotene, are found in yellow, orange, and green vegetables, egg yolk, liver, butter, and fish oils. Plants especially high in vitamin A include spinach, carrots, sweet potatoes, squash, and cantaloupe. In the plant kingdom, vitamin A, in a form known as retinol, functions as a free radical scavenger, protecting plants from UV radiation damage. To humans, retinol is also a valuable protectant against oxidative damage in our world.
As mentioned previously, oral vitamin A is an important endogenous antioxidant. Oxidation occurs due to formation of oxygen radical species, such as hydrogen peroxide, superoxide anion, and hydroxy radicals that transfer their energy to living human cells resulting in damage. Cellular proteins, enzymes, DNA, and RNA are damaged, but oxidative damage to the unsaturated fatty acid component of cell membranes is of primary importance. Hydroxy radicals initiate lipid peroxidation in cell membranes to form lipid peroxides that are responsible for the appearance of benign photodamage. One of the primary oxidation products thought to induce aging is malondialdehyde (MDA). Interestingly, MDA is also increased in cells that have undergone carcinogenesis. Oral vitamin A appears to have an effect on this process.
Recently, the use of topical forms of naturally occurring vitamin A in skin care products for benign photodamage has been popularized. Vitamin A can perform several different functions when topically applied. It is a known humectant, meaning that it can attract water from the dermis and viable epidermis to the stratum corneum. This aids in skin hydration when the humectant vitamin A is combined with an occlusive agent, such as petrolatum or mineral oil, to prevent water evaporation. Vitamin A can also function as preservative by preventing oxidation of the lipids in the moisturizer in the form of retinyl palmitate, however this naturally occurring form of vitamin A has no biologic activity.
There is some evidence that naturally occurring forms of vitamin A, such as retinyl palmitate and retinol, can function as topical antioxidants, enhancing functioning of benign photodamaged skin. It is now well recognized that the skin is an enzymatically active organ capable of metabolic alteration of topically applied substances. Retinyl palmitate can become biologically active following cutaneous enzymatic cleavage of the ester bond and subsequent conversion of retinol to retinoic acid. It is this cutaneous conversion of retinol to retinoic acid that is responsible for the biologic activity of some of the new stabilized over-the-counter vitamin A preparations designed to improve the appearance of benign photodamaged skin. Unfortunately, only small amounts of retinyl palmitate and retinol can be converted by the skin, accounting for the increased efficacy seen with prescription preparations containing retinoic acid, to be discussed next.
The vitamin A derivatives that have been discussed up to this point are considered nutritional supplements and thus are found in cosmetic preparations. Topical synthetic vitamin A derivatives, designed to alter the structure and function of benign photodamaged skin, include tretinoin (Retin-A, Renova, Ortho) and tazarotene (Tazorac, Avage, Allergan). The synthetic retinoids, as well as the naturally occurring forms of vitamin A, are difficult to formulate due to their inherent photo instability. As antioxidants, they degrade immediately upon light exposure to biologically inactive forms. For this reason, oral forms of synthetic and natural vitamin A are packaged in amber bottles to prevent UV radiation exposure and prescription topical retinoids are packaged in opaque metal or plastic tubes. Topical preparations where the retinoid has oxidized turn yellow, an indication that some degradation has occurred.
The remainder of this discussion focuses on the use of topical synthetic retinoids for purposes of decreasing and reversing the signs of benign photodamage. The use of retinoids in the reversal and prevention of photoaging was discovered by Albert Kligman, MD, Ph.D., who noted that topical tretinoin improved wrinkling, lentigenes, roughness, and precancerous actinic keratoses. The list of observed retinoid effects is summarized in Table 5.,
The initial effect observed following the first few weeks of topical tretinoin treatment is improvement in tactile smoothness. This is felt to be due to a stratum corneum with a more compact pattern with increased epidermal thickness due to spongiosis. Increased hyaluronic acid is also produced, allowing the water holding capacity of the skin to increase, also contributing to the early improvement in skin smoothness. Thickening also occurs in the epidermal granular cell layer. The effects of topical tretinoin following 4 months of use are improvement in fine wrinkles, representing a dermal effect. This improvement is due to an increase in collagen production. Furthermore, it has been demonstrated that tretinoin decreases UVB-induced collagenase activity, thus preventing photoaging. Topical tretinoin does prevent photoaging by acting as a sunscreen, since it does not reduce UVB-induced erythema. The improvement in skin condition continues with prolonged use and may be seen in both sun-exposed and sun-protected skin., Side effects are consistent with hypervitaminosis A of the skin and include mild skin irritation (erythema, peeling, burning) and a clinically insignificant burning sensation in the eyes.
Topical tretinoin also appears to have an effect on skin pigmentation as seen by a decrease in cutaneous freckling and lentigenes. It is the irregular grouping and activation of melanocytes that accounts for the dyspigmentation associated with photoaging, but normalization of this change has been histologically demonstrated by Bhawan, et al. Improvement in dyspigmentation has also been demonstrated in Oriental and Black skin.,
Thus, synthetic and naturally occurring retinoids form the foundation for topical agents designed to improve the appearance of benign photodamaged skin. The fact that skin cells possess a retinoid receptor provides direct access to altering the structure and function of the skin. There are other vitamins that have used to improve the appearance of photodamaged skin, to be discussed next, however their function is limited by the fact they are not receptor-mediated vitamins.
Stem cells are pluripotential cells that can differentiate into many different structures. The ability of stem cells to differentiate and remain differentiated is key to survival of complex multiorgan life, such as humans. Once differentiated, liver cells must remain liver cells, kidney cells must remain kidney cells, and skin cells must remain skin cells. This is accomplished through epigenetic changes that repress certain gene sequences that should no longer be transcribed. If these gene sequences are mistakenly available for transcription, cancer may occur. Yet, there is tremendous interest in stem cells as a source of materials for replenishing the aging body.
Stem cells are present in all organisms, including plants. One of the theories of how anti-aging skin care products might work is through the use of stem cells from plants, such as raspberries. The theory is that these ingredients might be effective in reducing oxidative stress on the skin thereby reducing inflammation. This article examines the role of plant stem cells in skin care, how the stem cells are used to obtain plant extracts, how the products are tested, and their relevance to dermatology.
Berry extracts from raspberries, blueberries, and strawberries have become an area of intense research is the cosmetics industry because they contain high levels of anthocyanins, representing a new category of highly potent antioxidants with anti-inflammatory activity. Berry extracts also contain other ingredients such as reservatrol, a polyphenol purported to modulate sirtuins, and ellagic acid, a purported antiviral and anticancer agent. Wild cultivars contain higher levels of these active ingredients than domesticated varieties. Many different parts of the plant can be used to obtain the extract.
Stem cells are used for the preparation of many extracts used in skin care products. The stem cells can be obtained from many different plant parts. The berries, leaves, stems, twigs, and roots can all be used. Commonly, the leaves of the plant are used because they are especially high in antioxidants, since the leaves are the site of photosynthesis and require excellent oxidative stress protection. The stem cells are cultured under controlled laboratory conditions to obtain the purest extract possible.
Plant materials obtained from outdoor cultivation may contain a variety of contaminants to include heavy metals, pesticides, and fungal toxins. When the plant material is concentrated, so are the contaminants. One of the biggest concerns with frequent green tea consumption is the possibility of pesticide intake, since pesticides are used to prevent leaf damage in the fields. It is not possible to remove the pesticides completely from the leaves and tea represents a concentrated use of the dried leaves. Utilizing stem cells eliminates this type of concern.
Stem cell derived materials also have greater consistency of contents. The plant materials are cultured under optimal conditions to yield a more standard composition than those grown outdoors that may vary based on weather, soil condition, fertilizer application, etc. Consistency is key to obtaining a reliable extract for reproducible results.
Many mistakenly think that the entire stem cell is placed in the skin care product, but this is not the case. The stem cell is used to obtain the extract that is then placed into formulation. It is not possible to maintain live stem cells in cosmetic emulsions. Osmotic conditions, lack of suitable growth media, and preservatives make this impossible.
Stem cells are obtained from the plant leaves after they have been sterilized in 70% ethanol for 15 minutes and 1% bleach for an additional 15 minutes followed by washing three times with sterile water. The original plant material for culture must come from outdoors, but all contaminants must be removed for successful culture. The leaves are then cut into thin 0.5cm pieces and placed on an agar culture plate containing plant growth hormones, such as kinetin. Plant callus is then formed that can be collected. The callus is then cultured to form single cells, which are recultured in a liquid media. The cells are then filtered for removal from the media and homogenized. The mixture is centrifuged to remove the soluble components and lyophilized to obtain a powder that represents the cosmetic ingredient.
The cosmetic ingredient that is obtained is not the viable stem cell, but the substances that are contained in the stem cell. These are the chemical entities that are then added to the anti-aging cream. An example of the constituents of a raspberry extract obtained in this manner is listed in Table 1. These are all potent antioxidants.
Assessing the antioxidant properties of a stem cell extract relies on techniques developed to assess the efficacy of food preservation. It is unlikely that these assays are directly applicable to antioxidant efficacy of the product on the skin, but these assessment techniques are currently considered state-of-the-art in the cosmetics industry. These techniques are the total antioxidant capacity (TAC) and the oxygen radical absorbance capacity (ORAC).
The TAC assay is used to measure the reducing ability of a substance. It is performed by mixing the test compound with copper II. If copper II is converted to copper I through a reduction reaction, the ingredient can be considered an effective antioxidant. This is a different technique than the ORAC assay where the ability of the ingredient to inhibit the oxidation of fluorescein in the presence of a potent oxidant (2,2’-azobis(2-amidinopropane) dihydrochloride) abbreviated AAPH is examined. These tests indicate that a material can function as an antioxidant in vitro, but the most significant oxidative damage occurs in the skin and not on the stratum corneum where the ingredient is applied. This is why in vitro testing is predictive, but not confirmatory.
How is this new stem cell technology relevant to dermatology? This is the first step in standardizing botanical cosmetic ingredients and achieving the consistency of dose mandatory in drug development. Stem cells also provide for purity that was previously not achievable. However, stem cell technology does not mean that plant cells can somehow interact with human cells to induce a slowing or reversal of aging like you might have seen in a new science fiction movie.
The use of stem cells to obtain better quality ingredients with consistent composition is a step forward in cosmetic technology. Variability of plant extracts has been a key source of concern. Drugs must possess consistent delivery each and every time they are used and cosmetic ingredient suppliers are searching for ways to improve cosmetic ingredient consistency. Stem cells offer an opportunity for consistency, but also ingredient purity. One of the reasons botanical extracts that have been submitted for FDA approval as drugs have been denied is due to contamination. Stem cells minimize this concern.