245 ex 3, wound healing & FDA

Discriminate between cell types?

Neutrophil = 3-lobed

Macrophage = single pinched

FBGCs = many nuclei

Would Healing

Extension into dermal layer requires repair

• First step is blood clotting and formation of a fibrin network to prevent fluid loss

• Second, acute inflammation begins which triggers influx in fibroblasts to begin formation of granulation tissues

  • Large number of new blood vessels form as well

• As new ECM is deposited, fibrin clot dissolved

• Final step is remodeling/scar formation, requires turnover of collagen molecules in the ECM along with collagen accumulation.

Skin Regeneration

If wound is contained in the epidermal layer, full regeneration is possible via re-epithelialization

• Cells at edge of wound change shape to cover the wound

  • Migrate into the wound

• Cells contact other epithelial cells within the wound and recover their original shape while reattaching to the ECM

• Further proliferation and matrix production occur to restore original thickness.

In Vivo Assays for Inflammatory Response

In vitro evaluation can not replace in vivo due to complex interplay of cell types and signaling molecules that comprise the immune response.

Considerations in Development of Animal Models

Animal

Implant Site

Length of Study

FDA

Regulates medical devices, regulatory framework in the US

Three primary roles: Gatekeeper, enforcer, sentinel

Medical device

device intended to be used to affect the body of a person in any manner.

Classes of devices (ISO 10993-1)

Cat 1: Surface-contacting - Bandage

Cat 2: External communicating - Pacemakers

Cat 3: Implant - Heart valves

Biological Evaluation

Three main tests

• Cytotoxicity

• Irritation (3-24hr)

• Sensitization (2-24hr)