Stratum corneum intercellular lipid and keratin matrix (SC matrix)

The stratum corneum intercellular lipid and keratin matrix is the primary physical barrier of the mammalian epidermis, often described by the "brick and mortar" model. In this structural assembly, the "bricks" are the corneocytes—dead, flattened cells filled with a dense matrix of keratin proteins and filaggrin—while the "mortar" is a continuous extracellular lipid matrix composed of ceramides, cholesterol, and free fatty acids (StatPearls, 2023). This complex is essential for maintaining homeostasis by preventing transepidermal water loss and protecting the body from environmental insults, including chemical irritants and microbial pathogens (Journal of Investigative Dermatology, 2012). In dermatological diseases such as atopic dermatitis and psoriasis, the integrity of this matrix is often compromised due to genetic mutations (e.g., filaggrin deficiency) or inflammatory processes, leading to a "leaky" barrier and increased sensitivity (PubMed, 2008). Therapeutic strategies target this matrix through the use of keratolytic agents to remove hyperkeratotic scales or barrier-repair formulations that aim to replenish the lipid cement and restore the skin's protective function (NIH, 2021). Understanding the biochemical composition of this matrix is critical for the development of topical drug delivery systems, as it represents the rate-limiting step for the penetration of most pharmacological agents.

Other names

Skin barrierBrick and mortar modelCorneocyte-lipid matrixEpidermal permeability barrierIntercellular cement

Keratolytic agents like salicylic acid and urea disrupt the desmosomal connections and the keratin matrix within corneocytes to promote desquamation. Emollients and barrier-repair agents (e.g., ceramides, cholesterol) replenish the intercellular lipid cement to restore the permeability barrier and reduce water loss. Humectants like glycerin draw water into the keratin matrix to increase skin flexibility.