The population group serving as a model for the tropoelastin composition are chosen for one or more characteristics and once the appropriate genes have been synthesized and introduced into a host organism, large quantities of human tropoelastin are produced by cultivation of transgenic plants. The elastin composition can then be formulated and incorporated as an ingredient in skin care compositions. This product provides a source of authentic human tropoelastin with the same characteristics as the material synthesized in the body, be compatible with the biochemistry of the skin, and can beidentified directly with the population that served as the source genetic code for the DNA used in the production of the material.

Recombinant Human Tropoelastin. The human tropoelastin gene has been cloned into E. coli and r-tropoelastin produced in small quantities by fermentation. The resulting purified material has been shown to be water soluble and to serve as a substrate for the crosslinking enzyme lysyl oxidase. Research has confirmed that recombinant human tropoelastin is incorporated into tissues. These studies also demonstrated that certain tropoelastin isomorphs are more efficiently incorporated into the tissue matrix.

Keratin. Human hair varies in length, thickness and color in different individuals and among different races. Hair consists of a root and a shaft. The shaft is made up of three parts: the medulla, the cortex and the cuticle. The medulla is composed of rows of polyhedral cells. The cortex constitutes the chief part of the hair shaft and its cells contain pigment granules in dark hair and air in white hair. The cuticle consists of a single layer of flat scales that overlap one another. Exposure of the hair to sun, wind, and modern hair styling techniques imparts significant damage to the proteins of the cuticle and cortex. As damage to hair proteins accumulates, a loss in body results in poor combability, increased electrostatic charging, breaking of the hair and the poor appearance of hairstyles.

The structural component of hair is an overlapping array of protein filaments. These filament proteins contain a rod domain, which assembles in pairs to form a dimeric coil. The dimers form multimer subunits, which twist and pack together into microscopic ropes that are woven together in different ways to form a network. This network connects cells to each other and is a major structural component of epithelial tissues. In humans, three-quarters of all filament proteins are made of the protein keratin (Lane et al., Current Opinion in Gen. and Dev. 1994, 4: pp 412-418.).

Keratins are the most complex group of filament proteins. There are at least 30 keratin proteins which can be further divided into hard keratins, (hair and nail keratins), and soft keratins, (epidermal keratins) (Yu et al., J. of Invest. Dermatol., 101, No. 1, Supplement, July, 1993; and Fuchs, Ann. Rev. Biochem., 63: pp. 345-382, 1994). At present, there are seven type I hair keratins (Winter et al. Nature Genetics, 1997, 16: pp. 372-374.) and four type II hair keratins (Rogers et al., Differentiation, 1997, 61: pp. 187-194.). Together with the so-called minor components the hair keratin family comprises 13 members. There is an astounding heterogeneity in keratin proteins expressed in different individuals. This heterogeneity results from a polymorphism of the respective epithelial keratin genes (Mischke et al., J. Invest. Dermatol. 1987, 88: # 2, pp. 191-197).
top
Given the heterogeneity of epidermal keratins and its effect on the appearance of the skin, it is not surprising that polymorphisms are also found to be associated with hair keratins. In one example, two polymorphic loci were identified and shown to be inherited as Mendelian traits (Winter et al.). Heterogeneity in keratin proteins can have direct effects on the tensile strength, flexibility, and dynamics of the intermediate filaments, which means that even subtle heterogeneity in intermediate filament proteins can influence the external features of the hair or skin.

Proteins are widely used in the formulation of hair care products to provide shine, strength, softness, smoothness, and good combing properties. Keratin in particular is often utilized. Because the naturally occuring cross linked keratin fibers are insoluble in water, the keratin is solubilized using chemical and enzymatic methods that hydrolyze the protein from starting materials including animal and human hair, feathers, claws, horns, hooves and scales. Since the keratin proteins are from a variety of sources they do not reflect any particular desirable keratin composition. Because the protein is hydrolyzed to its constituent amino acids, it does not maintain the structure of the keratin protein, but is merely a simple mixture of amino acids that is added to the hair treatment composition. An ideal hair treatment product would tailor the type of intact keratin used in the hair treatment product to match the hair keratins in a specific individual’s hair, or reproduce the keratin proteins of hair with specific desirable characteristics.