Induction of bone by epithelial cell products

Area of Science:

• Developmental Biology
• Cell Biology
• Biochemistry

Background:

• Craniofacial bone development in vertebrates requires inductive interactions between progenitor cells and embryonic epithelia.
• The specific role of epithelial products in initiating bone formation remains an area of investigation.

Purpose of the Study:

• To determine if extracellular products from epithelial cells can substitute for intact epithelia in inducing bone formation.
• To identify the component within epithelial basal lamina responsible for bone induction.

Main Methods:

• Culturing embryonic chick mandibular epithelia on Millipore filters to generate extracellular matrix.
• Grafting mandibular ectomesenchymal cells onto these matrices and assessing bone formation in vivo.
• Enzymatic treatments (trypsin, L-azetidine-carboxylic acid, hyaluronidase) to identify the inductive component.

Main Results:

• Epithelial extracellular matrix, identified as basal lamina-like, supported bone formation by mandibular ectomesenchyme.
• Trypsin and L-azetidine-carboxylic acid treatments abolished the inductive capacity of the extracellular products.
• Hyaluronidase treatment did not affect the induction of bone formation.

Conclusions:

• A proteinaceous component of the epithelial basal lamina is sufficient to induce bone differentiation in mandibular ectomesenchyme.
• This suggests a critical role for specific extracellular matrix proteins in craniofacial skeletal development.