Differentiating local and systemic inflammatory responses to burn injuries

Transplantation of human induced pluripotent stem cell derived keratinocytes accelerates deep second-degree burn wound healing

BACKGROUND

Current evidence shows that human induced pluripotent stem cells (hiPSCs) can effectively differentiate into keratinocytes (KCs), but its effect on skin burn healing has not been reported.

AIM

To observe the effects of hiPSCs-derived KCs transplantation on skin burn healing in mice and to preliminarily reveal the underlying mechanisms.

METHODS

An analysis of differentially expressed genes in burn wounds based on GEO datasets GSE140926, and GSE27186 was established. A differentiation medium containing retinoic acid and bone morphogenetic protein 4 was applied to induce hiPSCs to differentiate into KCs. The expression of KCs marker proteins was detected using immunofluorescence staining. A model of a C57BL/6 mouse with deep cutaneous second-degree burn was created, and then phosphate buffered saline (PBS), hiPSCs-KCs, or hiPSCs-KCs with knockdown of COL7A1 were injected around the wound surface. The wound healing, re-epithelialization, engraftment of hiPSCs-KCs into wounds, proinflammatory factor level, and the NF-κB pathway proteins were assessed by hematoxylin-eosin staining, carboxifluorescein diacetate succinimidyl ester (CFSE) fluorescence staining, enzyme linked immunosorbent assay, and Western blotting on days 3, 7, and 14 after the injection, respectively. Moreover, the effects of COL7A1 knockdown on the proliferation and migration of hiPSCs-KCs were confirmed by immunohistochemistry, EdU, Transwell, and damage repair assays.

RESULTS

HiPSCs-KCs could express the hallmark proteins of KCs. COL7A1 was down-regulated in burn wound tissues and highly expressed in hiPSCs-KCs. Transplantation of hiPSCs-KCs into mice with burn wounds resulted in a significant decrease in wound area, an increase in wound re-epithelialization, a decrease in proinflammatory factors content, and an inhibition of NF-κB pathway activation compared to the PBS group. The in vitro assay showed that COL7A1 knockdown could rescue the inhibition of hiPSCs-KCs proliferation and migration, providing further evidence that COL7A1 speeds up burn wound healing by limiting cell proliferation and migration.

CONCLUSION

In deep, second-degree burn wounds, COL7A1 can promote KC proliferation and migration while also suppressing the inflammatory response.

Burn-injured skin is marked by a prolonged local acute inflammatory response of innate immune cells and pro-inflammatory cytokines

The systemic and local immune response in burn patients is often extreme and derailed. As excessive inflammation can damage healthy tissues and slow down the healing process, modulation of inflammatory responses could limit complications and improve recovery. Due to its complexity, more detailed information on the immune effects of thermal injury is needed to improve patient outcomes. We therefore characterized and quantified subsets of immune cells and mediators present in human burn wound tissue (eschar), sampled at various time points. This study shows that after burn injury, the number of immune cells were persistently increased, unlike the normal wound healing process. There was an immediate, strong increase in neutrophils and a moderate increase in monocytes/macrophages and lymphocytes, especially in the second and third week post burn. The percentage of classical (CD14highCD16-) monocytes/macrophages demonstrated a steady decrease over time, whereas the proportion of intermediate (CD14highCD16+) monocytes/macrophages slowly increased. The absolute numbers of T cells, NK cells and B cells increased up to week 3, while the fraction of γδ T cells was increased only in week 1. Secretome profiling revealed high levels of chemokines and an overall pro-inflammatory cytokine milieu in burn tissue. The local burn immune response shows similarities to the systemic immune reaction, but differs in neutrophil maturity and lymphocyte composition. Altogether, the neutrophil surges, high levels of pro-inflammatory cytokines and limited immunosuppression might be key factors that prolong the inflammation phase and delay the wound healing process in burns.

Global burn care and the ideal burn dressing reloaded - A survey of global experts

PURPOSE

Burn care is a highly relevant medical specialty in every part of the world. Different infrastructure, healthcare systems and access to medical supplies lead to different needs, treatment strategies and outcomes. A fundamental tool in a burn care provider's armamentarium is the use of different dressings. Several studies have investigated the question of the ideal burn dressing, but none could achieve a proper global perspective. With advanced dressings being on the rise, we conducted this study to get a global understanding of the actual use and idea of the ideal burn dressing.

OBJECTIVE

The objective of this study was to investigate the understanding of an 'ideal burn dressing' on a global scale.

MATERIALS AND METHODS

A questionnaire about burn care and the ideal burn dressing has been created and translated to five of the most spoken languages world-wide (English, Spanish, French, Chinese, Indonesian). It has been uploaded to an online survey platform and sent out to burn experts worldwide. The voluntary participation was possible for a period of four weeks.

RESULTS

In total, 196 respondents from 49 countries participated in the study, yielding a response rate of 24.5%. The most important burn dressing characteristics in a cumulative ranking were (1) lack of adhesion (80.54%), (2) pain-free dressing change (79.87%), (3) requirement of fewer dressing changes, while in a linear ranking they were (1) anti-infective (35.14% 1st), pain-reduction (24.14% 2nd), and high absorbency (23.49% 3rd). Silver-based dressings are the most used dressings for superficial (45.21%) and deep (52.78%). 94.81% believe that the choice of burn dressing affects the outcome.

CONCLUSION

This investigation has delivered valuable insights into the global perspective of the ideal burn dressing. Yet, the question of the ideal burn dressing is still inconclusive. Wound dressing research is of fundamental interest for patients, healthcare providers and healthcare systems.