Pressure ulcers, which are also knows as bedsores (or decubitus ulcers) are localized injuries to the skin that can also include the underlying tissue that usually occur as a result of pressure, or pressure in combination with rubbing or friction. They tend to occur some sort of bony prominence such as elbows, hips, shoulders, ankles, back of the head, and other such places. More than 2.5 million patients each year in the U.S. require treatment for pressure ulcers, and the elderly are at particularly high risk for these lesions. Currently, therapies for pressure ulcers consist of conservative medical management for shallow lesions and aggressive debridement and surgery for deeper lesions.
Jeffery Gimble and his colleagues from the Tulane University School of Medicine in New Orleans, Louisiana, used a mouse model for pressure ulcers to test the ability of fat-derived stromal/stem cell treatment to accelerate and enhance the healing of pressure ulcers. The dorsal skin of both young (2 months old) and old (20 months old) C57BL/6J female mice was pinched between external magnets for 12 hours over 2 consecutive days. This treatment initiated a pressure ulcer, and one day after induction of the pressure ulcers, some of these mice were injected with fat-derived stromal stem cells that had been isolated from healthy mice that were of the same genetic lineage as the injured mice. However, the donor mice were genetically engineered to express a green fluorescent protein in all their tissues. Other mice were treated with injections of saline-treated controls.
The mice that were injected with fat-derived stromal/stem cells displayed a cell-concentration-dependent acceleration of wound closure. The cell-injected mice also showed improved epidermal/dermal architecture, increased fat deposition, and reduced inflammation at the sites of injury. Interestingly, these fat-derived stem cell-induced improvements occurred in both young and elderly mice. However, the gene expression profile of genes involved in the making of blood vessels, regulating the immune system, and tissue repair differed according to the age of the mice, with younger mice making more of these genes that their older counterparts. These results are consistent with clinical reports of the improved skin architecture after fat grafting in patients with thermal injuries.
This current proof-of-principle study sets the stage for clinical translation of the transplantation of fat-based stem cells as a treatment of pressure ulcers.