Intraluminal release of citrullinated histone 3 from various cellular origins coincides with microvascular thrombosis in burn wounds.

Loss of perfusion in the burn wound might cause wound deepening and impaired healing. We previously showed persistent microvascular thrombosis coinciding with intraluminal neutrophils extracellular traps in human burned skin. This study investigates the presence of intraluminal citrullinated histone 3 (H3cit) from different cellular origins (neutrophils, monocytes, and lymphocytes) in relation to microvascular thrombosis of burn wounds. Eschar was obtained from burn patients (n = 18) 6-40 days postburn with a mean total burned body surface area of 23%. Microvascular presence of tissue factor (TF), factor XII (FXII) and thrombi was assessed by immunohistochemistry. Intramicrovascular cell death was analyzed via immunofluorescent microscopy, combining antibodies for neutrophils (MPO), monocytes (CD14), and lymphocytes (CD45) with endothelial cell markers CD31 and H3cit. Significantly increased microvascular expression of TF, FXII, and thrombi (CD31+) was found in all eschar samples compared with control uninjured skin. Release of H3cit from different cellular origins was observed in the lumen of the dermal microvasculature in the eschar tissue 7-40 days postburn, with release from neutrophilic origin being 2.7 times more abundant. Intraluminal presence of extracellular H3cit colocalizing with either MPO, CD14, or CD45 is correlated to increased microvascular thrombosis in eschar of burn patients.

Scar formation from the perspective of complexity science: a new look at the biological system as a whole.

A burn wound is a complex systemic disease at multiple levels. Current knowledge of scar formation after burn injury has come from traditional biological and clinical studies. These are normally focused on just a small part of the entire process, which has limited our ability to sufficiently understand the underlying mechanisms and to predict systems behaviour. Scar formation after burn injury is a result of a complex biological system-wound healing. It is a part of a larger whole. In this self-organising system, many components form networks of interactions with each other. These networks of interactions are typically non-linear and change their states dynamically, responding to the environment and showing emergent long-term behaviour. How molecular and cellular data relate to clinical phenomena, especially regarding effective therapies of burn wounds to achieve minimal scarring, is difficult to unravel and comprehend. Complexity science can help bridge this gap by integrating small parts into a larger whole, such that relevant biological mechanisms and data are combined in a computational model to better understand the complexity of the entire biological system. A better understanding of the complex biological system of post-burn scar formation could bring research and treatment regimens to the next level. The aim of this review/position paper is to create more awareness of complexity in scar formation after burn injury by describing the basic principles of complexity science and its potential for burn care professionals.

Neutrophil extracellular traps coincide with a pro-coagulant status of microcirculatory endothelium in burn wounds.

Burn-induced tissue loss is partly related to secondary expansion of necrosis into vital dermis neighboring the initial burn injury. An important factor herein is the severe loss of perfusion of the burn wound, probably caused by microvascular damage induced by the intense local inflammatory responses as well as burn-induced hypercoagulation. We hypothesize that the formation of neutrophilic extracellular traps (NETs) play an important role in this. The purpose of this study was to investigate postburn intravascular thrombosis, NETs formation and the coagulant state in the microvasculature of burns in both animal models and patients. We used two in vivo burn wound models: rats and pigs. In rats, the entire wound was excised at day 14 postburn and in pigs burn wound biopsies were collected at different time points up to 60 days postburn. To confirm the data in patients, eschar from the burn wound was obtained from burn wound patients at different time points after wounding. The number of intravascular thrombi, the presence of intravascular NETs and the number of tissue factor (TF) positive blood vessels in the burn wound was determined. In rats, a significant increase in intravascular thrombi and TF expression was observed 14 days postburn, that in majority coincided with NETs. In pigs, a significant increase in intravascular thrombi and TF expression was found over time up to 60 days postburn, that in majority coincided with NETs too. Also in eschar of burn wound patients, a significant increase in intravascular thrombi was noted, that in majority coincided with NETs, already 0.5 days postburn and remained elevated up to 46 days postburn. This study shows the presence of NETosis in microcirculatory thrombosis of burn wounds and a switch in the microcirculatory endothelium toward a procoagulant phenotype.

Insulin-induced changes in skeletal muscle microvascular perfusion are dependent upon perivascular adipose tissue in women.

AIMS/HYPOTHESIS: Obesity increases the risk of cardiovascular disease and type 2 diabetes, partly through reduced insulin-induced microvascular vasodilation, which causes impairment of glucose delivery and uptake. We studied whether perivascular adipose tissue (PVAT) controls insulin-induced vasodilation in human muscle, and whether altered properties of PVAT relate to reduced insulin-induced vasodilation in obesity. METHODS: Insulin-induced microvascular recruitment was measured using contrast enhanced ultrasound (CEU), before and during a hyperinsulinaemic-euglycaemic clamp in 15 lean and 18 obese healthy women (18-55 years). Surgical skeletal muscle biopsies were taken on a separate day to study perivascular adipocyte size in histological slices, as well as to study ex vivo insulin-induced vasoreactivity in microvessels in the absence and presence of PVAT in the pressure myograph. Statistical mediation of the relation between BMI and microvascular recruitment by PVAT was studied in a mediation model. RESULTS: Obese women showed impaired insulin-induced microvascular recruitment and lower metabolic insulin sensitivity compared with lean women. Microvascular recruitment was a mediator in the association between obesity and insulin sensitivity. Perivascular adipocyte size, determined in skeletal muscle biopsies, was larger in obese than in lean women, and statistically explained the difference in microvascular recruitment between obese and lean women. PVAT from lean women enhanced insulin-induced vasodilation in isolated skeletal muscle resistance arteries, while PVAT from obese women revealed insulin-induced vasoconstriction. CONCLUSIONS/INTERPRETATION: PVAT from lean women enhances insulin-induced vasodilation and microvascular recruitment whereas PVAT from obese women does not. PVAT adipocyte size partly explains the difference in insulin-induced microvascular recruitment between lean and obese women.

An in silico modeling approach to understanding the dynamics of the post-burn immune response.

Introduction: Burns are characterized by a massive and prolonged acute inflammation, which persists for up to months after the initial trauma. Due to the complexity of the inflammatory process, Predicting the dynamics of wound healing process can be challenging for burn injuries. The aim of this study was to develop simulation models for the post-burn immune response based on (pre)clinical data. Methods: The simulation domain was separated into blood and tissue compartments. Each of these compartments contained solutes and cell agents. Solutes comprise pro-inflammatory cytokines, anti-inflammatory cytokines and inflammation triggering factors. The solutes diffuse around the domain based on their concentration profiles. The cells include mast cells, neutrophils, and macrophages, and were modeled as independent agents. The cells are motile and exhibit chemotaxis based on concentrations gradients of the solutes. In addition, the cells secrete various solutes that in turn alter the dynamics and responses of the burn wound system. Results: We developed an Glazier-Graner-Hogeweg method-based model (GGH) to capture the complexities associated with the dynamics of inflammation after burn injuries, including changes in cell counts and cytokine levels. Through simulations from day 0 - 4 post-burn, we successfully identified key factors influencing the acute inflammatory response, i.e., the initial number of endothelial cells, the chemotaxis threshold, and the level of chemoattractants. Conclusion: Our findings highlight the pivotal role of the initial endothelial cell count as a key parameter for intensity of inflammation and progression of acute inflammation, 0 - 4 days post-burn.

The Complexity of the Post-Burn Immune Response: An Overview of the Associated Local and Systemic Complications.

Burn injury induces a complex inflammatory response, both locally and systemically, and is not yet completely unravelled and understood. In order to enable the development of accurate treatment options, it is of paramount importance to fully understand post-burn immunology. Research in the last decades describes insights into the prolonged and excessive inflammatory response that could exist after both severe and milder burn trauma and that this response differs from that of none-burn acute trauma. Persistent activity of complement, acute phase proteins and pro- and anti-inflammatory mediators, changes in lymphocyte activity, activation of the stress response and infiltration of immune cells have all been related to post-burn local and systemic pathology. This "narrative" review explores the current state of knowledge, focusing on both the local and systemic immunology post-burn, and further questions how it is linked to the clinical outcome. Moreover, it illustrates the complexity of post-burn immunology and the existing gaps in knowledge on underlying mechanisms of burn pathology.

[What is the stat of art in 3D bioprinting of cartilage? Challenges concerning the reconstruction of a burned ear]. / Hoe staat het met 3D-bioprinten van kraakbeen?

Five years ago in this journal we described our research into 3D bioprinting of ear cartilage for the purpose of making personalized cartilage implants for facial reconstruction. 3D bioprinting makes it possible to place living cells in a biodegradable scaffold to give a 3D structure to the tissue. We are able to develop a hybrid auricular cartilage implant model. However, Long term in vivo experiments are needed to test preclinical applicability. Nevertheless, the work presented in our studies provides a potential strategy for the use of biofabricated tissue constructs in the clinic. In short, 3D bioprinting is still in its infancy and has no direct clinical application yet. Before the step to the clinic can be made, the technique still has to go through a preclinical phase in which it is investigated how the 3D printed tissue would appear in vivo.

NOX2 Expression Is Increased in Keratinocytes After Burn Injury.

Reepithelialization is crucial for effective wound repair in burn wounds. Reactive oxygen species (ROS) have shown to be important in this. Recent studies suggest that NOX proteins produce ROS in keratinocytes. In the present study, we have studied NOX proteins in burn wounds, including the effect of C1-esterase inhibitor (C1inh) hereon, which is the endogenous inhibitor of complement activity whereof we have shown previously that it also increased the rate of reepithelialization in burn wounds. Skin tissue derived from healthy control Wistar rats (n = 6) were compared with burn-injured rats, with (n = 7) or without C1inh treatment (n = 7). After 14 days, rats were terminated. From the burn-injured rats, the entire wound and nonburned skin from the hind leg, that is, internal control was excised. From the control rats, dorsal skin was excised. In these skin samples, NOX2 and NOX4 were analyzed immunohistochemically. In nonburned rats, NOX2 was found in keratinocytes in both the basal layer and suprabasal layer of the epidermis; and the number of NOX2-positive keratinocytes was 367/mm2 (254-378). In burned rats, the number of NOX2-positive keratinocytes was significantly increased in the newly forming epidermis in the burned area to 1019/mm2 (649-1172), especially in the suprabasal layer, but significantly decreased in remote nonburned skin to 22/mm2 (6-89). C1inh treatment counteracted these changes in epidermal NOX2 expression in burned rats, both in the burned area as in remote nonburned skin. No NOX4 expression was found in the epidermis in none of the groups. NOX2 expression was increased in keratinocytes in newly forming epidermis after burn injury. C1inh, a drug that increases the rate of reepithelialization, counteracted this effect. These results suggest a role for NOX2 in the reepithelialization of burn wounds.

Impact of delayed and prolonged fixation on the evaluation of immunohistochemical staining on lung carcinoma resection specimen.

Pre-analytical factors, such as fixation time, influence morphology of diagnostic and predictive immunohistochemical staining, which are increasingly used in the evaluation of lung cancer. Our aim was to investigate if variations in fixation time influence the outcome of immunohistochemical staining in lung cancer. From lung resections, specimen with tumor size bigger than 4 cm, 10 samples were obtained: 2 were put through the standard fixation protocol, 5 through the delayed, and 3 through the prolonged fixation protocol. After paraffin embedding, tissue microarrays (TMAs) were made. They were stained with 20 antibodies and scored for quality and intensity of staining. Samples with delay in fixation showed loss of TMA cores on glass slides and deterioration of tissue quality leading to reduction in the expression of CK 7, Keratin MNF116, CAM 5.2, CK 5/6, TTF-1, C-MET, Napsin A, D2-40, and PD-L1. Prolonged fixation had no influence on the performance of immunohistochemical stains. Delay of fixation negatively affects the expression of different immunohistochemical markers, influencing diagnostic (cytokeratins) and predictive (PD-L1) testing. These results emphasize the need for adequate fixation of resection specimen.

The role of complement in the acute phase response after burns.

Severe burns induce a complex systemic inflammatory response characterized by a typical prolonged acute phase response (APR) that starts approximately 4-8h after-burn and persists for months up to a year after the initial burn trauma. During this APR, acute phase proteins (APPs), including C-reactive protein (CRP) and complement (e.g. C3, C4 and C5) are released in the blood, resulting amongst others, in the recruitment and migration of inflammatory cells. Although the APR is necessary for proper wound healing, a prolonged APR can induce local tissue damage, hamper the healing process and cause negative systemic effects in several organs, including the heart, lungs, kidney and the central nervous system. In this review, we will discuss the role of the APR in burns with a specific focus on complement.

The Local and Systemic Inflammatory Response in a Pig Burn Wound Model With a Pivotal Role for Complement.

In patients with burns, a massive inflammatory response is induced which negatively affects the healing process of the burn wound and additionally exerts systemic effects. An important factor herein is the complement system. Here we analyzed the effects of burns on complement and inflammatory cells both locally and systemically after burn in time in a pig burn wound model. In burned pigs, burn wound biopsies and blood were collected up to 60 days after burn. Complement in blood as well as complement and inflammatory cells in the burn wound and several organs were determined. In the blood, C3 was significantly increased after 9 to 60 days, whereas C4 after 21 to 30 days after burn. In the burn wound, C3 levels were significantly increased after 9 days and C4 after 3 days, whereafter both declined after 21 and 9 days, respectively. Neutrophils, macrophages, and lymphocytes were significantly increased in the burn wound after 3 days, all declined after 21 days after burn. In the heart, at 60 days after burn, an increase of neutrophils and macrophages was observed, mainly in the right atrium. In contrast to the heart, the inflammatory cell infiltrates in the lungs, liver, and kidney of burned pigs were lower than in control pigs. In pigs, following burn there is a prolonged increase in complement levels both in the burn wound and the blood and increased inflammatory cell infiltrate in the burn wound and the heart. However, complement levels in the burn wound and in the blood seem not to be correlated in time.

Myocardial Microvascular Inflammatory Endothelial Activation in Heart Failure With Preserved Ejection Fraction.

OBJECTIVES: The present study investigated whether systemic, low-grade inflammation of metabolic risk contributed to diastolic left ventricular (LV) dysfunction and heart failure with preseved ejection fraction (HFpEF) through coronary microvascular endothelial activation, which alters paracrine signalling to cardiomyocytes and predisposes them to hypertrophy and high diastolic stiffness. BACKGROUND: Metabolic risk is associated with diastolic LV dysfunction and HFpEF. METHODS: We explored inflammatory endothelial activation and its effects on oxidative stress, nitric oxide (NO) bioavailability, and cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) signalling in myocardial biopsies of HFpEF patients and validated our findings by comparing obese Zucker diabetic fatty/Spontaneously hypertensive heart failure F1 hybrid (ZSF1)-HFpEF rats to ZSF1-Control (Ctrl) rats. RESULTS: In myocardium of HFpEF patients and ZSF1-HFpEF rats, we observed the following: 1) E-selectin and intercellular adhesion molecule-1 expression levels were upregulated; 2) NADPH oxidase 2 expression was raised in macrophages and endothelial cells but not in cardiomyocytes; and 3) uncoupling of endothelial nitric oxide synthase, which was associated with reduced myocardial nitrite/nitrate concentration, cGMP content, and PKG activity. CONCLUSIONS: HFpEF is associated with coronary microvascular endothelial activation and oxidative stress. These lead to a reduction of NO-dependent signalling from endothelial cells to cardiomyocytes, which can contribute to the high cardiomyocyte stiffness and hypertrophy observed in HFpEF.

Analysis of morphological characteristics and expression levels of extracellular matrix proteins in skin wounds to determine wound age in living subjects in forensic medicine.

OBJECTIVE: Wound age determination in living subjects is important in routine diagnostics in forensic medicine. Macroscopical description of a wound to determine wound age however is inadequate. The aim of this study was to assess whether it would be feasible to determine wound age via analysis of morphological characteristics and extracellular matrix proteins in skin biopsies of living subjects referred to a forensic outpatient clinic. METHODS: Skin biopsies (n=101), representing the border area of the wound, were taken from skin injuries of known wound age (range: 4.5h-25 days) in living subjects. All biopsies were analyzed for 3 morphological features (ulceration, parakeratosis and hemorrhage) and 3 extracellular matrix markers (collagen III, collagen IV and α-SMA). For quantification, biopsies were subdivided in 4 different timeframes: 0.2-2 days, 2-4 days, 4-10 days and 10-25 days old wounds. Subsequently, a probability scoring system was developed. RESULTS: For hemorrhage, collagen III, collagen IV and α-SMA expression no relation with wound age was found. Ulceration was only found in wounds of 0.2-2, 2-4 and 4-10 days old, implying that the probability that a wound was more than 10 days old in case of ulceration is equal to 0%. Also parakeratosis was almost exclusively found in wounds of 0.2-2, 2-4 and 4-10 days old, except for one case with a wound age of 15 days old. The probability scoring system of all analyzed markers, as depicted above, however can be used to calculate individual wound age probabilities in biopsies of skin wounds of living subjects. CONCLUSIONS: We have developed a probability scoring system, analysing morphological characteristics and extracellular matrix proteins in superficial skin biopsies of wounds in living subjects that can be applied in forensic medicine for wound age determination.

Analysis of inflammatory cells and mediators in skin wound biopsies to determine wound age in living subjects in forensic medicine.

OBJECTIVE: In forensic medicine it is important to determine the age of skin wounds in living subjects. The aim of this study was to assess whether analysis of inflammatory cells and inflammatory mediators in skin biopsies of wounds from living subjects could improve wound age determination. METHODS: Biopsies (n=101), representing the superficial border area of a skin wound, were taken from skin injuries of known wound age (range: 4.5 hours to 25 days) of living subjects. All biopsies were analyzed for 3 inflammatory cell markers (MPO, CD45 and CD68) and 4 inflammatory mediators (MIP-1, IL-8, CML and vitronectin). For quantification, biopsies were subdivided in 4 different timeframes: 0.2-2 days, 2-4 days, 4-10 days and 10-25 days old wounds. Subsequently, a probability scoring system was developed. RESULTS: MPO, CD45, MIP-1, IL-8 (inflammatory cell markers) and N(epsilon)-(carboxymethyl)lysine (CML) positivity were maximal in wounds of 0.2-2 days old and then decreased in time. Remarkably, CD45, CD68 and CML showed a minor but non-significant increase again in 10-25 days old wounds. MPO and CD68 positivity was significantly lower in 4-25 days old wounds compared to 0.2-4 days old wounds. MPO positivity was also significantly lower in 10-25 days old wounds compared to 0.2-10 days old wounds. For CD45, MIP-1, IL-8 and CML no significant differences between the age groups were found. In case of vitronectin positivity in the extravasate or when the number of MIP-1 or IL-8-positive cells was more than 10 cells/mm(2) the probability that a wound was more than 10 days old was 0%. A probability scoring system of all analyzed markers can be used to calculate individual wound age probabilities in biopsies of skin wounds of living subjects. CONCLUSIONS: We have developed a probability scoring system of inflammatory cells and mediators that can be used to determine wound age in skin biopsies of living subjects.

A new method to determine wound age in early vital skin injuries: a probability scoring system using expression levels of Fibronectin, CD62p and Factor VIII in wound hemorrhage.

PURPOSE OF THE STUDY: In forensic autopsies it is important to determine the age of early vital skin wounds as accurate as possible. In addition to inflammation, coagulation is also induced in vital wounds. Analysis of blood coagulation markers in wound hemorrhage could therefore be an important additional discriminating factor in wound age determination. The aim of this study was to develop a wound age probability scoring system, based on the immunohistochemical expression levels of Fibronectin, CD62p and Factor VIII in wound hemorrhage. METHODS: Tissue samples of (A) non injured control skin (n=383), and samples of mechanically induced skin injuries of known wound age, (B) injuries inflicted shortly before death (up to a few minutes old) (n=382), and (C) injuries inflicted 15-30 min before death (n=42) were obtained at autopsy in order to validate wound age estimation. Tissue slides were stained for Fibronectin, CD62p and Factor VIII and were subsequently scored for staining intensity (IHC score) in wound hemorrhage (1=minor, 2=moderate, 3=strong positive). Finally, probability scores of these markers were calculated. RESULTS: In at most 14% of the non-injured control samples, hemorrhage was found, with mean±standard deviation IHC scores of 0.1±0.4, 0.2±0.4 and 0.2±0.5 for Fibronectin, CD62p, and Factor VIII, respectively. Expression of these markers significantly increased to mean IHC scores 1.4±0.8 (Fibronectin), 1.2±0.6 (CD62p), and 1.6±0.8 (Factor VIII) in wounds inflicted shortly before death (few minutes old) and to 2.6±0.5 (Fibronectin), 2.5±0.6 (CD62p), and 2.8±0.4 (Factor VIII) in 15-30 min old wounds. The probabilities that a wound was non vital in case of an IH score 0 were 87%, 88% and 90% for Fibronectin, CD62p, and Factor VIII, respectively. In case of an IHC score 1 or 2, the probabilities that a wound was a few minutes old were 82/90%, 82/83% and 72/93%. Finally, in case of an IHC score 3, the probabilities that a wound was 15-30 min old were 65%, 76% and 55%. CONCLUSIONS: Based on the expression of Fibronectin, CD62p and Factor VIII in wound hemorrhage, we developed a probability scoring system that can be used in forensic autopsies to improve wound age estimation in early skin injuries.