A NEW STRATEGY TO MODULATE ALOPECIA 47 Up to a hundred hair are shed every day (6). Over that number, pathological hair loss (alopecia) is most likely to occur. Male pattern hair loss (androgenic alopecia) is the most common type of baldness, affecting roughly 50% of Caucasian men by the age of 50 years and 13% of Caucasian women before menopause increasing to 75% by the age of 65 years in women (5). Asians and African are less affected than Caucasians and the incidence is lowest in Native Americans and Eskimos (6). Patterns of hair loss may vary among gen- ders. Indeed in men, the crown and temples are more likely to be fi rst affected, a pattern that eventually progresses to baldness, whereas in women hair loss is generally rather dif- fuse (7). In most cases, hair thinning appears to precede hair loss (8). The causes of male pattern hair loss are still a matter of debate, but genetic predisposi- tion, hormonal dysfunction, loss of extracellular matrix (ECM) proteins in the follicular bed, and localized microinfl ammation are recognized as major triggers (Figure 2). From a hormonal point of view, androgens are known to be important regulators of hair growth and the enzyme 5-α-reductase is pivotal to their effect. In the scalp, testosterone is metabolized to the stronger androgenic signal 5-α-dihydrotestosterone (DHT) by 5-α-reductase. Besides its action on androgen receptors in the follicle, DHT also stimu- lates the synthesis of transforming growth factor (TGF)-β in dermal papilla cells. TGF-β signaling is associated with inhibition of keratinocyte growth and induction of cell apoptosis (9). Pathological expression of TGF-β is a source of infl ammation and fi brotic matrix deposition (10). In hair physiology, TGF-β is a catagen inducer that also pre- vents reentry from telogen to anagen, thus suppressing hair growth (11). Higher 5-α-reductase activity, resulting in high levels of DHT and dysregulated TGF-β sig- naling, is found in bald scalp (12). Cell–matrix interactions are also key regulatory steps in hair cycling (13). The ECM is in constant remodeling during the different phases of hair growth. Maintenance of the ECM composition is mainly assumed by the dermal papilla fi broblasts, but proper exchange with hair matrix keratinocytes is mandatory for this function. These exchanges take place at the basement membrane zone (BMZ) located at the epithelial–mesenchymal interface of the hair follicle. Matrix proteins found at this interface serve as anchors to maintain Figure 2. Pathological mechanisms involved in recessing hair: combined effects of hormones, infl ammation, and ECM dysfunction alter the hair growth cycle and lead to hair loss.

JOURNAL OF COSMETIC SCIENCE 48 epithelial–mesenchymal contact and stabilize the BMZ. These include laminins, some integrins, and collagen VII (14,15). They have a crucial role in the maintenance of the hair follicle and the control of its volume. Microinfl ammation is suspected to be a precipitating factor in male pattern alopecia (16), but the concept has yet to be integrated into treatment strategies. Exposure to irritants, pollution, and UV radiation has the potential to turn keratinocytes into mediators of infl ammation (17). Under stress conditions, keratinocytes react by increasing their production of interleukin (IL)-1α, a pro-infl ammatory cytokine. The latter acts on fi broblasts to stimulate their production of IL-8, a cytokine involved in the recruit- ment of neutrophils. Both IL-1α and IL-8 are inducible at the dermal papilla and were found in plucked hair samples of subjects with male pattern alopecia (18) sug- gesting their participation in the pathology (19). Cytokine-driven persistent infl am- mation also activates matrix metalloproteinases involved in tissue remodeling and perifollicular fi brosis (20). Limited treatments are currently available for male pattern alopecia. The most popular are the following: minoxidil (Rogain® McNeil-PPC, Johnson & Johnson, New Bruns- wick, New Jersey, USA.), an over-the-counter vasodilator that is believed to optimize blood supply to the dermal papilla (5) fi nasteride (Propecia® Merck, Whitehouse Station, New Jersey), a drug that acts by inhibiting the enzyme that converts testosterone to DHT (5) and diaminopyrimidine oxide (Aminexil®, l’Oréal, Paris, France), a patented compound that prevents perifollicular fi brosis. Each of these treatments targets one aspect of hair loss and offers a certain level of effi cacy for those who respond. However, for improved results, it may be desirable to simultaneously target several aspects of the problem. The new cosmetic active ingredient (a mixture of clover extract and acetyl tetrapeptide-3), described in this article, represents a new, more integrative approach to hair loss. MATERIAL AND METHODS TEST MATERIAL The test material consisted of a mixture of Trifolium pratense (clover) fl ower extract (total isofl avone ≥98% and biochanin A ≥12%, determined by high-performance liquid chro- matography (HPLC)) and acetyl tetrapeptide-3 (pure peptide obtained by solid phase peptide synthesis, purity ≥90% determined by HPLC). The clover extract fraction is standardized using biochanin A, a phytoestrogen fl avonoid with documented health- promoting activities (20). The tetrapeptide is a biomimetic derived from a signal peptide found in matrix proteins, such as collagen and fi brin, and also in HGF, which is a growth factor fi rst isolated from human plasma (21). The peptide is normally liberated by prote- olysis in the course of tissue damage. Its release and activation stimulates tissue remodel- ing following the initial phase of wound healing. The components of the mixture were tested either together or alone, according to their expected roles in hair care, as could be deduced from the existing literature (20,22). An effect of the biochanin A component was documented on 5-α-reductase activity, while acetyl tetra- peptide-3 was investigated for its infl uence on ECM components, including collagens III and VII, and laminins. The mixture of both components was tested for anti-infl ammatory activity before being clinically tested in humans to evidence effi cacy in reducing hair loss.