Burn wounds are notoriously susceptible to bacterial infection and usually result in a greater amount of scar tissue than laceration wounds.
in APL Bioengineering, With the publication of the AIP, researchers from Boston University and Harvard University have created a biomimetic model to study wound healing in burn and laceration wounds. They discovered that fibroblasts—usually considered building cells that give shape and strength to tissues and organs—remove damaged tissue before depositing new material. This part of the healing process is slower in burn wounds, as there is more tissue damage.
Cell biologists identify four stages of wound healing: cessation of bleeding, inflammation, new tissue formation, and tissue strengthening. During the inflammatory and formation stages, immune cells are thought to remove bacteria and dead cells from the wound. It also activates fibroblasts and blood vessels to initiate repairs.
Depending on the injury, the extent and duration of these four stages can vary widely across different types of wounds. Given that laceration wounds are well filled with blood, they tend to heal well. However, in the case of burns, the blood vessels are cauterized, which prevents blood from entering the wound bed and slows down the healing process. Severe burn wounds also contain large amounts of dead tissue that physically prevents new tissue from forming.”
Jeroen Ekmans, author
To study how injury affects the rate of wound healing, the team designed an in vitro model system made of fibroblasts embedded in a collagen hydrogel. Wounds were created in these delicate tissues using a microdissection knife to simulate laceration or a high-energy laser to simulate a burn.
Although the two types of wound were of equal size, laser ablation caused more cell death and tissue damage adjacent to the wound margins than knife wounds.
“During healing, we found that fibroblasts first removed damaged material from the wound before depositing new material,” Ekmans said. “This was a surprising finding because the removal of dead tissue was attributed to specialized immune cells such as macrophages, and fibroblasts were considered tissue-building cells, not tissue-clearing cells.”
Because there was more tissue damage in laser ablation wounds, it took more time for the fibroblasts to remove the damage, which ultimately delayed tissue healing.
Based on these findings, therapies that promote wound clearance can accelerate healing. Genetically modified white blood cells, which are designed to remove dead tissue, could be especially useful for reaching injured organs and tissues deep in the body.
Gribble, M.; et al. (2023). Removal of damaged tissue fibroblasts after microengineered tissue laser ablation. APL Bioengineering. doi.org/10.1063/5.0133478.