Temple University School of Podiatric Medicine Journal Review Club

Editor's note: This post is part of the Temple University School of Podiatric Medicine (TUSPM) journal review club blog series. In each blog post, a TUSPM student will review a journal article relevant to wound management and related topics and provide their evaluation of the clinical research therein.

Article Title: Stem cells derived from burned skin – The future of burn care

Authors: Saeid Amini-Nik; Reinhard Dolp; Gertraud Eylert; Andrea-Kaye Datu; Alexandra Parousis; Camille Blakeley; Marc G. Jeschke (Sunnybrook Research Institute, Canada)

Journal: EBioMedicine

Reviewed by: Akhil Korrapati, Class of 2021, Temple University School of Podiatric Medicine

Introduction

Thermal injuries outrank the combined incidence rates of both HIV and tuberculosis, making a thermal injury one of the most devastating injuries a patient can incur. The single most crucial factor for burn patients in terms of survival is wound coverage and wound healing. The current standard for burn wounds is to excise the injury within 72 hours. Extracting the damage reduces the source of inflammatory stimuli as well as pathologic responses like keloid formation and hypertrophic scarring. After the removal of burned skin, autologous skin grafting is the current gold standard. Grafting is an invasive procedure and creates a new wound in a healthy skin area. The larger the burn, the less healthy skin remains for autologous skin grafting, limiting its availability for grafts. Realizing the limitations with skin grafting, the researchers turned to stem cells as a new alternative for wound healing. Fibroblast-like cells from surrounding intact cells as well as recruited mesenchymal progenitor cells contribute to the reconstitution of the dermis. Recent data is showing that myeloid lineage cells may directly convert into fibroblast-like cells and assist in dermis reconstitution. The researchers report that severely burned skin—which is routinely excised and discarded and considered as medical waste—contains viable MSC (burn-derived mesenchymal stem cells, BD-MSCs) that can be used for skin regeneration and wound healing. The researcher’s data demonstrates that BD-MSCs facilitates the healing process and decreases healing time.

Methods/Materials

The research team used excised human skin from patients that suffered at least a third-degree burn. Twenty-four hours after skin excision and cell extraction, an average of 16,140 ± 5,416 viable cells per cm2 of burned skin was attached to the plastic surface of the cell culture flask. They observed cell outgrowth from the skin into the tissue culture dish. These cells form colonies in a colony-forming assay and could differentiate into three lineages of mesenchymal cell progeny (adipogenic, chondrogenic, osteogenic differentiation), confirming their multipotent capacity. The research team then had four differentiation staining techniques, Oil Red O staining for Adipogenic differentiation, Alizarin red staining for Osteogenic differentiation, Alician Blue staining for chondrogenic differentiation and finally immunofluorescent adipogenic cell culture staining. After confirming the pluripotency and safety of BD-MSc, the researchers evaluated the reparative and regenerative potential of these cells in 10 mice and four pigs.

Results

Mice treated with BD-MSCs visibly displayed faster healing. Histological examination of the healed wounds at day 12 post-wounding showed a significantly smaller wound size, as well as a thinner keratinocyte layer in the BD-MSC group. At day 12, the mice that received BD-MSCs passed the proliferation phase and showed a lower proliferation profile which is characteristic of late proliferation phase and early remodeling phase. After determination of the safety and positive effect of BD-MSC treatment in mice, the researchers used a porcine wound-model with 5x5cm excisional wounds. BD-MSC treatment of excisional wounds in the porcine model showed the pro-wound healing properties of BD-MSCs obtained in the previous mice study. Beside enhanced re-epithelialization, the researchers observed an increase in the number of blood vessels in the dermal component of reconstituted skin, another characteristic of improved skin healing. No safety concerns or adverse effects were detected in wounds treated with BD-MSCs.

Discussion

The researchers claim to show for the first time that full-thickness burned skin, which is usually discarded to avoid further morbidities, contains viable mesenchymal skin stem cells originating from the injured organ itself. Since the cells are the patient's skin stem cells, the chance of immunological reaction and rejection is negligible and this does not raise ethical issues that represent an obstacle to embryonic or cadaverous stem cell extraction. Almost no patient refused to donate these discarded tissues, making such therapies universally applicable. Also, cell isolation from burned skin is a non-invasive technique with no added risk to the patient since the debridement of affected burned tissues is part of routine practice. Regarding the mice study, the researchers could detect human BD-MSCs in the scar/wound tissue of mice after complete wound closure. However, it was unclear if those cells were still in their MSC-state or if they could integrate and further differentiate to fully regenerate the skin. The pig study showed an increased epithelialization speed and area, confirming the acceleration of wound healing by BD-MSC treatment. Furthermore, a significantly higher number of new blood vessels have been observed in wounds treated with BD-MSC. More studies are underway to evaluate whether the enhanced neovascularization is the result of general enhanced wound healing or if there is a direct effect of BD-MSCs on neovascularization.

About the Author

Akhil Korrapati is a second-year podiatric medical student at Temple University School of Podiatric Medicine (TUSPM) in Philadelphia, Pennsylvania. He graduated from the University of Pittsburgh with a Bachelor of Arts in Health Services and a minor in Exercise Science. Akhil worked as a Research Coordinator at the Johns Hopkins School of Public Health and completed his Master of Science in Biotechnology. In the fall of 2017, he enrolled at TUSPM with a merit scholarship. Akhil holds a keen interest in diabetic limb salvage, wound care, and reconstructive surgery and hopes to use his platform as a future podiatrist to educate and increase awareness on the importance of lower extremity health including preventive care for chronic diseases, including diabetes and obesity. Dr. James McGuire is the director of the Leonard S. Abrams Center for Advanced Wound Healing and an associate professor of the Department of Podiatric Medicine and Orthopedics at the Temple University School of Podiatric Medicine in Philadelphia.