Fibronectin extracellular matrix assembly by human epidermal cells implanted into athymic mice

Area of Science:

• Dermatology
• Tissue Engineering
• Extracellular Matrix Biology

Background:

• Human epidermal keratinocytes (HEKs) implanted subcutaneously into athymic mice reorganize into epidermal inclusion cysts.
• This process offers a model to study epithelial organization and basement membrane formation in vivo.

Purpose of the Study:

• To investigate the temporal and spatial dynamics of extracellular matrix (ECM) and basement membrane protein deposition during the in vivo organization of HEKs into epidermal cysts.
• To compare the protein deposition sequence with that observed during skin wound reepithelialization.

Main Methods:

• Subcutaneous implantation of HEKs into athymic mice.
• Immunohistochemical analysis of cyst formation over time (up to 5 weeks).
• Detection of fibronectin, bullous pemphigoid antigen (BPAg), and laminin using species-specific antibodies.

Main Results:

• Fibronectin accumulation occurred early during cyst aggregation and persisted for 7 days, with some synthesized by implanted cells.
• Bullous pemphigoid antigen and laminin appeared later, forming a continuous band at the epithelial-stromal interface by 4 and 7 days, respectively.
• This basement membrane structure remained stable for at least 5 weeks, while fibronectin levels diminished.

Conclusions:

• Implanted human epidermal keratinocytes can establish and maintain a stable basement membrane zone in vivo.
• The observed sequence of fibronectin, BPAg, and laminin deposition parallels natural skin wound reepithelialization.
• This model is valuable for studying epithelial morphogenesis and basement membrane dynamics.