The dermal epidermal junction (DEJ) in the skin is the layer responsible for supporting the epidermis and epidermal-dermal adhesion and for the communication between epidermal and dermal cells. Traditionally, the study of the mechanisms of skin aging has overlooked this important area. The DEJ is a basement membrane that separates the skin cells (basal layer of keratinocytes) and anchoring fibril (composed largely of type VII collagen) in/from the epidermis from the extracellular matrix (ECM) in the dermis. This membrane is composed of two layers, the basal lamina, in contact with the epidermal cells, and the reticular lamina in contact with the dermis. The basement membrane contains specific structures/molecules that ensure the stability of the connection and communication between the two major skin compartments. The cohesion between dermis and epidermis is essential to maintain skin balance because it enables the transport of oxygen, nutrients and waste to the epidermis. The basal lamina is abundant in collagen type IV, proteoglycans and the glycoproteins entactin and laminin. These molecules provide a structural network and bioadhesive properties for cell attachment. The membrane, however, serves more than simple structural and filtering roles.

The laminins are a family of multi-domain glycoproteins that are an integral part of the structural scaffolding in almost every tissue of an organism. Laminins are major proteins in the basal lamina of the skin, forming a protein network in the ECM of the base membrane for the maintenance of DEJ architecture and stability. Laminin is, after collagen, the most abundant protein in the ECM of the base membrane at DEJ. The laminins are an important and biologically active part of the basal lamina, influencing cell differentiation, migration, adhesion and cutaneous regeneration. These mechanisms are necessary for skin maintenance and for healing mechanism. Keratinocytes bind to specific domain on Laminin using their own integrin receptors -the transmembrane proteins located on specific junction points called hemidesmosomes. Defects in laminins are involved in some skin pathologies.

Laminins are trimeric proteins that contain an α, β, and γ-chain. The isoforms of laminin molecules vary in chain composition. A number of chain combinations have been identified in vivo. The trimeric proteins can bind to other cell membrane and extracellular matrix molecules as well as bind to other laminins which allows them to form laminin aggregates. Laminins networks are associated with type IV collagen networks via entactin, fibronectin (a glycoprotein), and perlecan (a proteoglycan). They also bind to cell membranes through integrin receptors and other plasma membrane molecules. Through these interactions, laminins critically contribute to cell attachment and differentiation, cell shape and movement, maintenance of tissue phenotype, and promotion of tissue survival. Some of these biological functions of laminin have been associated with specific amino-acid sequences or fragments of laminin.

Studies have confirmed the involvement of the basement membrane in skin aging due to the early alteration of the membrane’s constituents during the aging process. Certain features of the DEJ are altered by the aging process, such as the anchoring ability of keratinocytes with age. Laminin synthesis has also been proved to decrease in aged skin. The production of laminins was reported to be reduced by 31% with age, in
reconstructed skin models. This causes a loss of contact between dermis and epidermis, and results in the skin losing elasticity and becoming saggy. In UV exposed skin, laminins are destroyed, resulting in the disorganization of the DEJ.

Biomimetic peptides are ingredients derived from the skin’s natural protein or peptides that function to mimic the activity of the protein/peptide in vivo. Biomimetic laminin peptides (peptides contain partial laminin sequence) has been developed for topical skin care and cosmetics. In vitro studies concerning the properties of the laminin peptide and its effects on human skin cells has been conducted. Lipotec has developed a laminin peptide ingredient named Serilesine® which is a hexapeptide from the alpha chain of Laminin. This peptide retains many of the characteristics of the native protein, and promotes cell adhesion and proliferation. Serilesine is able to restore the skin’s normal function by promoting synthesis of Laminin, stimulating keratinocyte and fibroblast proliferation, inducing a redensifying effect on the dermis, and an improvement in skin elasticity, compactness, tonicity and smoothness. ChroNOline™ is the commercial anti-aging ingredient manufactured by Atrium which targets specifically to the dermal-epidermal junction functionality. ChroNOline™ is able to boost the production of DEJ components such as collagen VII, laminin, and fibronectin. ChroNOline™ stimulates the production of laminin and fibronectin by human fibroblasts in in vitro and ex vitro studies. Addition of ChroNOline™ to human fibroblasts increased the production of laminins by 26%.