Anti-inflammatory effect of interleukin-6 highly enriched in secretome of two clinically relevant sources of mesenchymal stromal cells.

Despite several advances in the field of regenerative medicine, clinical management of extensive skin wounds or burns remains a major therapeutic issue. During the past few years, Mesenchymal Stromal Cells (MSCs) have emerged as a novel therapeutic tool to promote tissue repair through their anti-inflammatory, pro-trophic and pro-remodeling effects. They exert their biological activity mainly via the secretion of soluble bioactive molecules such as cytokines, growth factors, proteins and microRNAs which can be encapsulated within extracellular vesicles (EV). The recent discovery of their high plasticity to external stimuli has fostered the development of new targeted therapies known as priming strategies, to enhance their potential. Our team recently showed that Interleukin-1ß (IL-1ß)-primed gingival MSCs promote wound healing and epidermal engraftment in vitro, and in vivo through their secreted products that contain extracellular vesicles. In the present work, we investigated whether two common sources of MSCs, gingiva and bone marrow, could respond similarly to IL-1ß to favor pro-healing capabilities of their secretome. We showed that both primed-MSC sources, or their related secreted products, are able to reduce inflammation in LPS-challenged human monocytic THP-1 cell line. IL-1ß priming enhanced MSC secretion of wound healing-related growth factors, cytokines and miRNAs in both sources. Among them, interleukin 6 was shown to be involved in the anti-inflammatory effect of MSC secreted products. Overall, these results underline the pro-healing properties of both MSC sources and their secretome upon IL-1ß priming and their potential to improve the current medical treatment of severe wounds.

IL-1ß-Primed Mesenchymal Stromal Cells Improve Epidermal Substitute Engraftment and Wound Healing via Matrix Metalloproteinases and Transforming Growth Factor-ß1.

Since the 1980s, deep and extensive skin wounds and burns are treated with autologous split-thickness skin grafts, or cultured epidermal autografts, when donor sites are limited. However, the clinical use of cultured epidermal autografts often remains unsatisfactory because of poor engraftment rates, altered wound healing, and reduced skin functionality. In the past few decades, mesenchymal stromal cells (MSCs) have raised much attention because of their anti-inflammatory, protrophic, and pro-remodeling capacities. More specifically, gingival MSCs have been shown to possess enhanced wound healing properties compared with other tissue sources. Growing evidence also indicates that MSC priming could potentiate therapeutic effects in diverse in vitro and in vivo models of skin trauma. In this study, we found that IL-1ß-primed gingival MSCs promoted cell migration, dermal-epidermal junction formation, and inflammation reduction in vitro, as well as improved epidermal substitute engraftment in vivo. IL-1ß-primed gingival MSCs had different secretory profiles from naive gingival MSCs, characterized by an overexpression of transforming growth factor-ß and matrix metalloproteinase (MMP) pathway agonists. Eventually, MMP-1, MMP-9, and transforming growth factor-ß1 appeared to be critically involved in IL-1ß-primed gingival MSC mechanisms of action.

Influence of fibrin matrices and their released factors on epidermal substitute phenotype and engraftment.

Cultured epithelial autografts (CEAs) represent a life-saving surgical technique for full-thickness skin burns covering more than 60% total body surface area. However, CEAs present numerous drawbacks leading to heavy cosmetic and functional sequelae. In our previous study, we showed that human plasma-based fibrin matrices (hPBM) could improve the reparative potential of CEAs. Therefore, in the present work, we sought to investigate the role of hPBM compared with fibrin from purified fibrinogen (FPF) or plastic support on epidermal substitute formation and engraftment. The use of hPBM for epidermal substitute culture improved keratinocyte migration, proliferation, and epidermal substitute organization to a better extent than FPF in vitro. Both fibrin matrices favored greater dermal-epidermal junction protein deposition and prevented their degradation. Keratinocyte differentiation was also decreased using both fibrin matrices. Basement membrane protein deposition was mainly influenced by matrix whereas growth factors released from fibrin especially by hPBM were shown to enhance in vitro keratinocyte migration, proliferation, and epidermal substitute organization. Ultimately, epidermal substitutes grown on hPBM displayed better engraftment rates than those cultured on FPF or on plastic support in a NOD-SCID model of acute wound with the formation of a functional dermal-epidermal junction. Together, these results show the positive impact of fibrin matrices and their released growth factor on epidermal substitute phenotype and grafting efficiency. Fibrin matrices, and especially hPBM, may therefore be of interest to favor the treatment of full-thickness burn patients.

Bioengineering a human plasma-based epidermal substitute with efficient grafting capacity and high content in clonogenic cells.

UNLABELLED: Cultured epithelial autografts (CEAs) produced from a small, healthy skin biopsy represent a lifesaving surgical technique in cases of full-thickness skin burn covering >50% of total body surface area. CEAs also present numerous drawbacks, among them the use of animal proteins and cells, the high fragility of keratinocyte sheets, and the immaturity of the dermal-epidermal junction, leading to heavy cosmetic and functional sequelae. To overcome these weaknesses, we developed a human plasma-based epidermal substitute (hPBES) for epidermal coverage in cases of massive burn, as an alternative to traditional CEA, and set up critical quality controls for preclinical and clinical studies. In this study, phenotypical analyses in conjunction with functional assays (clonal analysis, long-term culture, or in vivo graft) showed that our new substitute fulfills the biological requirements for epidermal regeneration. hPBES keratinocytes showed high potential for cell proliferation and subsequent differentiation similar to healthy skin compared with a well-known reference material, as ascertained by a combination of quality controls. This work highlights the importance of integrating relevant multiparameter quality controls into the bioengineering of new skin substitutes before they reach clinical development. SIGNIFICANCE: This work involves the development of a new bioengineered epidermal substitute with pertinent functional quality controls. The novelty of this work is based on this quality approach.