Keratin and stratum corneum protein matrix (SC matrix)

The keratin and stratum corneum protein matrix constitutes the primary physical barrier of the human skin, located in the outermost layer of the epidermis. This matrix is composed of keratin intermediate filaments bundled by filaggrin within corneocytes, which are further encased in a cornified envelope and embedded in a lipid-rich extracellular matrix (StatPearls, Physiology, Stratum Corneum, 2023). Its primary biological function is to prevent transepidermal water loss and protect the body from environmental insults, including pathogens, chemicals, and UV radiation. In various dermatological diseases such as psoriasis, ichthyosis, and actinic keratosis, the matrix undergoes pathological thickening or abnormal differentiation, known as hyperkeratosis (PubMed, Keratolytic agents in dermatology, 2021). Therapeutic intervention often involves the use of keratolytic agents like salicylic acid or urea, which work by breaking down the protein bonds or increasing the hydration of the keratin matrix to facilitate the shedding of dead skin cells (PubChem, Salicylic Acid, 2024). Additionally, the high affinity of certain antifungal drugs for keratin allows for effective treatment of dermatophyte infections localized within this matrix.

Other names

Stratum corneumCornified envelopeKeratin matrixEpidermal barrierHorny layer

Keratolytic agents work by increasing the hydration of the stratum corneum or by dissolving the intercellular 'cement' (desmosomes) that holds corneocytes together, leading to the softening and shedding of the keratin layer. Some drugs, like terbinafine, exhibit high keratin affinity, allowing them to persist in the matrix to treat fungal infections.