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Wound healing of the integument in the 5-day chick embryo
Insights
This study details chick embryo wound healing, showing complete epidermal closure within 24 hours. It reveals basement membrane and epidermal cell changes during this rapid embryonic wound repair process.
Area of Science:
- Developmental Biology
- Regenerative Medicine
- Cell Biology
Background:
- Embryonic wound healing is crucial for development.
- Understanding the early stages of tissue repair is vital for regenerative medicine.
- Chick embryos offer a rapid model for studying complex biological processes like wound healing.
Purpose of the Study:
- To investigate the morphological changes during embryonic wound healing.
- To analyze the cellular and extracellular matrix dynamics post-excision in chick embryos.
- To characterize the timeline of basement membrane and epidermal cell reconstitution.
Main Methods:
- Light and electron microscopy were employed.
- A surgical excision of epidermis and mesenchyme was performed on 5-day chick embryos.
- Wound healing was observed at various time points from minutes to 30 hours post-operation.
Main Results:
- Complete wound closure occurred within 24 hours in all embryos.
- Early changes included epidermal cell rearrangement and basement membrane (lamina densa) folding.
- Epidermal migration began at 3 hours, with direct cell-cell contact, and basement membrane reconstruction by 24-30 hours.
Conclusions:
- Embryonic wound healing is a rapid process involving significant cellular and matrix remodeling.
- The basement membrane undergoes dynamic changes, with temporary loss and subsequent reconstitution during epidermal migration.
- Direct cell-to-cell interactions facilitate epidermal coverage in the absence of a complete basement membrane.
Abstract:
A morphological study of wound healing has been performed by light and electron microscopy in 5-day chick embryos. The operation consisted in the excision of a rectangular piece of epidermis and subjacent mesenchyme from the right flank. After 18 hours, 61% of the embryos were completely healed. Wound closure was completed in all embryos within 24 hours. Shortly after the operation, the basal epidermal cells at the wound edge enlarged and lost their regular arrangement. The intercellular spaces disappeared. The peridermal cells became thicker and acquired a rounded and swollen appearance. The lamina densa of the basement membrane showed a folded appearance near its free edge (2 minutes after the excision). The mesodermal face of the plasma membrane of the basal epidermal cells was deprived of lamina densa over a distance of approximately 4 micrometers from the wound edge. The epidermis began to migrate 3 hours after the excision. After 8 hours of wound healing, the lamina densa was progressively reconstituted by deposits of irregular and non uniformly dense material. The bare mesoderm showed a disorganized cellular arrangement with numerous blood cells and many phagocytes. Between 5 and 8 hours, the surface of the mesenchyme became epithelized. After 24 hours, the bare epithelized mesenchyme progressively took the appearance of a normal predermal dense mesenchyme. During the migration of the epidermis from the wound edges, no lamina densa was present between epidermal and dermal cells. Basal epidermal cells established direct contacts and zones of close parallel apposition with dermal cell processes. Between 24 and 30 hours, the lamina lucida and lamina densa were completely reconstructed in their normal appearance.