Human neonatal keratinocytes have very high levels of cellular vitamin A-binding proteins

Area of Science:

• Biochemistry
• Dermatology
• Cell Biology

Background:

• Cellular retinol-binding proteins (CRBP) and cellular retinoic acid-binding proteins (CRABP) are crucial for vitamin A's role in epidermal differentiation.
• Understanding the distribution of these binding proteins in skin layers is essential for elucidating vitamin A metabolism and function.

Purpose of the Study:

• To quantify the levels of CRBP and CRABP in the epidermis and dermis of newborn human foreskin.
• To compare these levels with those found in primary cultures of keratinocytes and fibroblasts.

Main Methods:

• Ligand binding assays were employed using radiolabeled all-trans-retinol and all-trans-retinoic acid.
• Cytosols from skin layers and cultured cells (keratinocytes, fibroblasts) were analyzed for binding protein quantification.

Main Results:

• Epidermal CRABP and CRBP levels in newborn foreskin were significantly higher than in adult epidermis but comparable to neonatal keratinocyte cultures.
• CRABP levels were substantially lower in the dermis compared to the epidermis, consistent with fibroblast cultures.
• Cultured dermal fibroblasts exhibited very low CRBP levels, indicating another dermal cell type likely contributes significantly to dermal CRBP.

Conclusions:

• Neonatal epidermis and keratinocytes possess high concentrations of CRABP and CRBP.
• Dermal fibroblasts have low CRABP levels, while their low CRBP levels suggest a non-fibroblast source for dermal CRBP.
• These findings highlight differential expression of vitamin A binding proteins in skin compartments and cell types.