The Role of Autophagy in the Maintenance of Mitochondrial Quality and Adaptations to Contractile Activity

Autophagy is a critical survival mechanism facilitating protein turnover and pathogen defense in post-mitotic cells. More recently, mitophagy has been identified for the selective recognition and targeting of mitochondria for degradation. Mitochondrial availability is the net result of organelle catabolism via mitophagy and mitochondrial biogenesis. Although the latter process has been well described, mitophagy in skeletal muscle is less understood, and it is unknown how these two opposing mechanisms converge during contractile activity. We employed an in vitro model of chronic contractile activity (CCA) of myotubes in cell culture in the presence of autophagy inhibitor Bafilomycin A1 (BafA) and assessed the implications of defective autophagy on the adaptations to contractile activity. BafA lead to severe deficits to mitochondrial respiration and enhanced reactive oxygen species. CCA ameliorated this defective phenotype, reverting levels back towards untreated controls. Thus, contractile activity normalizes mitophagy flux and maintains a healthier mitochondrial profile during autophagy deregulation

Stem cells derived from burned skin - The future of burn careResearch in context

Background: Thermal injuries affect millions of adults and children worldwide and are associated with high morbidity and mortality. The key determinant for the survival of burns is rapid wound healing. Large wounds exceed intrinsic wound-healing capacities, and the currently available coverage materials are insufficient due to lack of cellularity, availability or immunological rejection. Methods: Using the surgically debrided tissue, we isolated viable cells from burned skin. The isolated cells cultured in tissue culture dishes and characterized. Findings: We report here that debrided burned skin, which is routinely excised from patients and otherwise considered medical waste and unconsciously discarded, contains viable, undamaged cells which show characteristics of mesenchymal skin stem cells. Those cells can be extracted, characterized, expanded, and incorporated into created epidermal-dermal substitutes to promote wound healing in immune-compromised mice and Yorkshire pigs without adverse side effects. Interpretation: These findings are of paramount importance and provide an ideal cell source for autologous skin regeneration. Furthermore, this study highlights that skin contains progenitor cells resistant to thermal stress. Fund: Canadian Institutes of Health Research # 123336. CFI Leader's Opportunity Fund: Project # 25407 National Institutes of Health 2R01GM087285-05A1. EMHSeed: Fund: 500463, A generous donation from Toronto Hydro. Integra© Life Science Company provided the meshed bilayer Integra© for porcine experiments. Keywords: Mesenchymal stem cells, Wound healing, Skin, Burn, Trauma, Cell therapy, Autologous, Skin regeneratio

Burn Induces Browning of the Subcutaneous White Adipose Tissue in Mice and Humans

Burn is accompanied by long-lasting immuno-metabolic alterations referred to as hypermetabolism that are characterized by a considerable increase in resting energy expenditure and substantial whole-body catabolism. In burned patients, the length and magnitude of the hypermetabolic state is the highest of all patients and associated with profoundly increased morbidity and mortality. Unfortunately, the mechanisms involved in hypermetabolism are essentially unknown. We hypothesized that the adipose tissue plays a central role for the induction and persistence of hypermetabolism post-burn injury. Here, we show that burn induces a switch in the phenotype of the subcutaneous fat from white to beige, with associated characteristics such as increased mitochondrial mass and UCP1 expression. Our results further demonstrate the significant role of catecholamines and interleukin-6 in this process. We conclude that subcutaneous fat remodeling and browning represent an underlying mechanism that explains the elevated energy expenditure in burn-induced hypermetabolism

Biological characteristics of stem cells derived from burned skin—a comparative study with umbilical cord stem cells

Abstract Introduction Burned human skin, which is routinely excised and discarded, contains viable mesenchymal stromal/stem cells (burn-derived mesenchymal stromal/stem cells; BD-MSCs). These cells show promising potential to enable and aid wound regeneration. However, little is known about their cell characteristics and biological function. Objectives This study had two aims: first, to assess critical and cellular characteristics of BD-MSCs and, second, to compare those results with multipotent well-characterized MSCs from Wharton’s jelly of human umbilical cords (umbilical cord mesenchymal stromal/stem cells, UC-MSCs). Methods BD- and UC-MSCs were compared using immunophenotyping, multi-lineage differentiation, seahorse analysis for glycolytic and mitochondrial function, immune surface markers, and cell secretion profile assays. Results When compared to UC-MSCs, BD-MSCs demonstrated a lower mesenchymal differentiation capacity and altered inflammatory cytokine secretomes at baseline and after stimulation with lipopolysaccharides. No significant differences were found in population doubling time, colony formation, cell proliferation cell cycle, production of reactive oxygen species, glycolytic and mitochondrial function, and in the expression of major histocompatibility complex I and II and toll-like receptor (TLR). Importance, translation This study reveals valuable insights about MSCs obtained from burned skin and show comparable cellular characteristics with UC-MSCs, highlighting their potentials in cell therapy and skin regeneration

Skin regeneration is accelerated by a lower dose of multipotent mesenchymal stromal/stem cells—a paradigm change

Abstract Background Multipotent mesenchymal stromal/stem cell (MSC) therapy is under investigation in promising (pre-)clinical trials for wound healing, which is crucial for survival; however, the optimal cell dosage remains unknown. The aim was to investigate the efficacy of different low-to-high MSC dosages incorporated in a biodegradable collagen-based dermal regeneration template (DRT) Integra®. Methods We conducted a porcine study (N = 8 Yorkshire pigs) and seeded between 200 and 2,000,000 cells/cm2 of umbilical cord mesenchymal stromal/stem cells on the DRT and grafted it onto full-thickness burn excised wounds. On day 28, comparisons were made between the different low-to-high cell dose groups, the acellular control, a burn wound, and healthy skin. Result We found that the low dose range between 200 and 40,000 cells/cm2 regenerates the full-thickness burn excised wounds most efficaciously, followed by the middle dose range of 200,000–400,000 cells/cm2 and a high dose of 2,000,000 cells/cm2. The low dose of 40,000 cells/cm2 accelerated reepithelialization, reduced scarring, regenerated epidermal thickness superiorly, enhanced neovascularization, reduced fibrosis, and reduced type 1 and type 2 macrophages compared to other cell dosages and the acellular control. Conclusion This regenerative cell therapy study using MSCs shows efficacy toward a low dose, which changes the paradigm that more cells lead to better wound healing outcome