Engineered stem cell sheet enhances grafts for treating severe burns

Written by Alexandra Thompson

Biomedical engineers at Michigan Technological University (Houghton, MI, USA) have developed an improved graft technique for healing burns using an engineered sheet of stem cells to enhance the split thickness skin grafts.

Researchers from Michigan Technological University (Houghton, MI, USA) and the First Affiliated Hospital of Sun Yat-sen University (Guangzhou, China) have combined the split thickness skin graft (STSG) technique with a specially engineered sheet of stem cells to create an engineered tissue that maximizes the body’s natural healing power, resulting in improved burn wound repair in a rat model.

Treating burns requires regrowing or replacing the skin as well as ensuring the tissue is vascularized. Full-thickness skin grafts are currently the gold standard for treating burn wounds, but are not always feasible. “STSG can be used under unfavorable conditions, such as a recipient’s wound having moderate infection or less vasculature, where full thickness skin grafts would fail,” Feng Zhao, an associate professor of biomedical engineering at Michigan Tech, explained. “However, STSG are more fragile than full thickness skin grafts and can contract significantly during the healing process.”

Zhao engineers ‘pre-vascularized’ tissues that help the healing process begin more quickly by reducing graft contraction and encouraging early vascularization. The team uses stem cells to improve healing via release of growth factors and cytokines.

In a rat model of the combined stem cell sheet and STSG, the implantation demonstrated less contracted and puckered skin, less cellular inflammation and a thinner epidermal thickness. Improved blood microcirculation and preservation of complex structures such as hair follicles and sebaceous glands were also observed in the skin tissue.

Zhao commented on the results and hopes for its application: “The engineered stem cell sheet will overcome the limitation of current treatments for extensive and severe wounds, such as for acute burn injuries, and significantly improve the quality of life for patients suffering from burns.”

Significant outstanding challenges include the fragility of both the STSGs and stem cell sheets, and the difficulty in harvesting. Further work will therefore involve enhancing the mechanical properties of the cell sheets and improving harvesting techniques and technologies, as well as better understanding the processes behind the therapeutic effects.

“We have seen excellent therapeutic effects of the vascularized stem cell sheet in healing full skin wounds. However, the underlying mechanism needs to be further elucidated,” Zhao commented. “We also need to conduct large animal experiments, such as in pigs, which are closer to human physiology.”