Matrix metalloproteinase 9 modulates collagen matrices and wound repair

Area of Science:

• Zebrafish models for injury and regeneration
• Molecular mechanisms of wound healing
• Extracellular matrix remodeling

Background:

• Leukocyte infiltration characterizes acute and chronic injuries.
• Matrix metalloproteinase 9 (Mmp9) is implicated in injury, but its role in wound repair is unclear.
• A zebrafish mutant with chronic inflammation and epithelial defects was previously identified.

Purpose of the Study:

• To investigate the role of Mmp9 in zebrafish models of acute and chronic injury.
• To elucidate Mmp9's function in epithelial and collagen organization during wound repair.

Main Methods:

• Microarray analysis of mutant zebrafish larvae to identify gene expression changes.
• Mmp9 depletion using morpholino injection.
• Second-harmonic generation imaging to assess collagen fiber organization.
• Assessment of tissue regeneration after tail transection.

Main Results:

• Mutant larvae exhibited increased inflammatory gene expression, including significant Mmp9 upregulation.
• Mmp9 depletion partially rescued chronic inflammation and epithelial phenotypes, restoring collagen organization.
• Acute wounding induced Mmp9 expression and collagen thickening; Mmp9 depletion impaired this reorganization and tail regeneration.

Conclusions:

• Mmp9 plays a critical role in regulating both acute and chronic tissue damage.
• Mmp9 is essential for proper collagen reorganization during wound repair.
• Mmp9 is implicated in tissue regeneration following injury.